Systems, methods and devices for underground mining

Abstract

The present disclosure relates to systems, methods and devices for forming a void for underground mining, such as for forming a blasting or ventilation void for use in mining an ore body, tunnel or other underground mining operation. In some embodiments, the blasting or ventilation voids are formed in backfill material.

Description

10062563561Systems, methods and devices for underground miningField of the invention

[0001] This application claims priority from Australian provisional application 2025900987, filed on 26 March 2025, PCT application PCT / AU2025 / 050429, filed 30 April 2025, and Australian complete application 2025267473, filed on 14 November 2025. The entirety of these disclosures is hereby incorporated herein by reference.

[0002] The present disclosure relates to systems, methods and devices for forming a void for underground mining, such as for forming a blasting or ventilation void for use in mining an ore body, tunnel or other underground mining operation.Background of the invention

[0003] Metals and minerals are often found in underground deposits formed as a body or vein of ore contained in rock strata located at a range of depths. A technique for accessing and retrieving the ore from ore bodies in underground mining is referred to as “stoping” or “open stoping” or “long hole stoping”. This is a process of drilling blast holes, e.g. between tunnels or drives provided at two levels within or adjacent to a body of ore. The blast holes are then charged and detonated or blasted causing broken material from the ore body to collapse, e.g. to the tunnel or drive at the lower level, for collection and removal to the surface for processing.

[0004] Once all the ore has been removed from a stope, the resultant void or space is backfilled to reinforce the excavated area and to facilitate the mining of future stopes within the mining sequence, including the next adjacent stope. The term “stope” refers to the block or section of the ore body that is currently being mined. The dimensions of a stope may vary considerably from mine to mine. As an example, a stope in a particular mine may be about 20 metres high, about 20 metres deep and about 5 metres in width. The ore body will often lie or extend in the ground at an angle to a vertical and / or a horizontal plane, but it may also extend substantially vertically. After removing the blasted ore, the stope is backfilled with a backfill material, which may include rock, crushed aggregate, mine tailings, concrete, cemented rock fill, and / or paste fill (or combinations of the these). The backfill material and the method of backfilling can vary greatly between mining operations. Paste fill is an example of a flowable backfill10062563562material and is usually introduced by pumping the backfill material into the open stope or void. Where waste rock or cemented rock fill is used as backfill, the material is usually tipped or deposited into the open stope or void, e.g. by means of a front-end loader or other mechanical means.

[0005] For the charges in the blast holes to work successfully to break up the ore body, there must be space into which the rock can expand when the charges are detonated or “fired”. To this end, an initial void (i.e. a blasting void) is typically created in the stope to be mined to provide a space to which the rock may expand or break. This blasting void can be known by different names in the mining industry, such as a slot, rise, long hole rise, raise, raise bore, winze and box hole. The name of the blasting void is typically reflective of the method used to create the void, although the terms can at times be used interchangeably. Stopes require a blasting void and the process of establishing a blasting void is a difficult, costly and high-risk stage of mining a stope. A blasting void can be created either with specialised equipment, such as a raise bore rig, box hole rig, etc, or established using a standard production drill rig and explosives.

[0006] One example of a known blasting void creation technique is a raise bore slot. This methodology begins by drilling a pilot hole into the ore body from a top level (such as from an upper ore drive) to a bottom level (such as a lower ore drive). The pilot hole is then reamed using a suitable reamer head, which is typically attached to the drill rod at the lower level and then pulled up from the bottom level to the top level, in order to increase the diameter or width / depth of the hole. After removal of the raise bore cuttings and demobilisation of the raise bore rig or similar equipment used to form the hole, a series of blast holes are drilled around the hole. The blast holes are then loaded with explosives and fired towards the hole, thereby establishing a larger void, i.e. the slot.

[0007] Another example of a known blasting void technique, very similar to the raise bore slot technique, is known as the box hole slot. The main difference between the raise bore slot technique and the box hole slot technique is that rather than pulling the reamer head through between two levels, the reamer head is pushed from one level to another.

[0008] Yet another example of a known blasting void technique is known as the long hole slot / rise technique. A long hole slot is established by creating a hole with a long10062563563hole drill in a similar manner to a ‘burn cut’ used in drill and blast tunnelling. This process involves drilling multiple blast holes in close proximity around a series of larger ‘reamer holes’. The diameter of the reamer holes is typically between about 152 mm to 204 mm, whilst the blast holes are typically between 76 mm and 102 mm in diameter. The reamer holes provide a void for the blast holes to blast towards, thereby forming the final, larger blasting void. Long hole rises are generally fired in multiple ‘firings’ to increase the chance of successfully producing the final rise. The long hole rise technique is a common method used throughout the mining industry to establish a blasting void.

[0009] The above techniques involve forming the blasting void in the ore body. AU 2016305485 makes very brief reference to the possibility of adopting the long hole slot / rise technique or the raise bore slot technique in the backfill material, specifically describing creation of a void by mining an elongated substantially vertical or inclined shaft extending between a lower level and an upper level of the mine.

[0010] Newer techniques have also been explored for creating blasting voids in the mining industry. Some of these techniques have included deploying a hollow tubular casing or an inflatable bladder in an open stope, prior to backfilling operations. The premise behind these newer techniques is to effectively cast into the backfill material the blasting void. In the case of the hollow tubular casing, the blasting void is effectively the bore of the tubular casing, whereas when the inflatable bladder is used, the premise that the backfill material is cast around the inflatable bladder, followed by removal of the bladder to leave behind a blasting void.

[0011] In addition to the above, ‘crush firing’ methodology has also been utilised in some applications. This involves not forming a blasting void but instead blasting towards the backfill material (given its lesser compressive strength). This methodology has many shortcomings relative to methodology that involves creating a blasting void as the energy from a blast can be absorbed or otherwise dissipated by the backfill material, resulting in poor blasting outcomes.

[0012] Creation of the blasting void using many of the conventional blasting void creation techniques takes about six to seven days (i.e. 12 to 14 shifts) to complete, with factors such as poor ground conditions potentially causing delays. As such, a significant10062563564amount of time required in the mining cycle for stoping or long hole stoping is spent simply establishing the blasting void.

[0013] It will be appreciated that the creation of voids in underground mining is not a practice exclusive to stoping. Voids can be created in underground mining for various applications, including for ventilation purposes. Ventilation voids are typically called shafts. A typical process for forming a shaft may involve simply excavating a hole in a suitable location. The shaft may be left unsupported in some cases. In other cases, the shaft may be supported using rock bolts, concrete, etc. To support the shaft with rock bolts, miners have to be deployed into the shaft to install the rock bolts. A known methodology of doing this involves filing the shaft with loose rock, slowly removing a portion of the loose rock to allow miners into the shaft (the miners using the remaining loose rock as a platform) and for rock bolts to be installed. This process is repeated several times, with rock bolts installed at predetermined depths within the shaft, until all the loose rock has been removed. Understandably, such a methodology presents risk to the miners, but this methodology is generally employed anyway as it is more effective than leaving a shaft unsupported given the integrity of an unsupported shaft will deteriorate over time.

[0014] It is desirable to provide improved methodology, as well as associated systems and devices, for creating voids during underground mining more efficiently than at least some of the known techniques. Alternatively, it is desirable to provide the public with useful alternative methodology, as well as associated systems and devices, for creating voids during underground mining.

[0015] Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and / or combined with other pieces of prior art by a skilled person in the art.Summary of the invention

[0016] In a first aspect, the present invention provides a method of creating one or more blasting voids during underground mining, said one or more blasting voids10062563565configured to allow expansion of blasted material during a stope firing, the method including: excavating, in a backfill material near an interface between the backfill material and an unexcavated stope, a plurality of holes extending into the backfill material, said plurality of holes disposed in a predetermined pattern such that the plurality of holes define one or more blasting voids.

[0017] In an embodiment, the backfill material is a flowable backfill material. In an embodiment, the flowable backfill material includes a paste fill, mine tailings, concrete or similar. In another embodiment, the backfill material is a non-flowable backfill material. In an embodiment, the non-flowable backfill material includes rock (e.g. waste rock, crushed rock, etc.), crushed aggregate, cemented rock fill, or similar.

[0018] In an embodiment, two or more of the plurality of holes are disposed in close proximity to one another such that said two or more holes together define one of the one or more blasting voids. It will be understood that disposing the plurality of holes in close proximity to one another to define a blasting void can mean 1 ) that two or more of the holes may intersect one another along their respective lengths, 2) that any unexcavated material disposed between adjacent, non-intersecting holes is of little structural integrity so as to effectively create a continuous void due to providing minimal resistance to blasting operations, or 3) a combination of 1) and 2).

[0019] It will be appreciated that whilst the focus of the method is to excavate the plurality of holes solely in the backfill material near the interface between the backfill material and the unexcavated stope, the uneven nature of the rock face (i.e. along the face of the unexcavated stope) may mean that in excavating the plurality of holes, partial excavation of the hard rock material associated with the unexcavated stope may occur.

[0020] It will be understood that by ‘near’ in reference to excavating the plurality of holes near the interface between the backfill material and the unexcavated stope, it is meant that the plurality of holes are arranged such that they are within a suitable distance of the blast holes so that the blast can propagate through burden disposed between the blast holes and the plurality of holes. In other words, the plurality of holes are arranged at a suitable distance to the interface between the backfill material and the unexcavated stope such that the blast can propagate through to the one or more10062563566blasting voids. Preferably, the plurality of holes in the backfill material are as close to the interface between the backfill material and the unexcavated stope as possible / practical (whilst substantially extending into the backfill material). A person skilled in the art will appreciate that the precise positioning of the holes can be different from mine to mine, as well as different for different ore bodies. Other factors will be the size of the plurality of holes forming the one or more blasting voids, as well as the size, shape and arrangement of the blast holes in the unexcavated stope.

[0021] In an embodiment, excavating said plurality of holes includes excavating said plurality of holes in said predetermined pattern in the backfill material. It will be appreciated that said predetermined pattern may be selected based at least partly on the geometry of a rock face at the interface between the backfill material and the unexcavated stope, including where the rock face is uneven (for example curved inwardly or outwardly) such that the interface is not planar. Accordingly, in some embodiments the predetermined pattern (i.e. location and / or orientation of one or more holes of the predetermined pattern) may be tailored to account for such geometry so as to position the plurality of holes near the interface and thereby define the one or more blasting voids. In an embodiment, said predetermined pattern includes arranging two or more of the plurality of holes near to one another and / or arranging two or more of the plurality of holes such that they intersect with one another. In an embodiment, said predetermined pattern includes a substantially linear row of holes adjacent to one another. In an embodiment, said substantially linear row of holes are arranged substantially in a longitudinal direction, which coincides with a general direction of an underground ore drive or the strike of the ore body. In an embodiment, said substantially linear row of holes are arranged substantially in a transverse direction, perpendicular to the longitudinal direction and perpendicular to a height direction of the unexcavated stope. In an embodiment, said substantially linear row of holes are arranged substantially in a transverse direction, perpendicular to the longitudinal direction and parallel to a height direction of the unexcavated stope. In an embodiment, said predetermined pattern includes a plurality of substantially linear rows of holes, each row being spaced apart from one another. For the avoidance of doubt, reference to a substantially linear row of holes includes a plurality of holes arranged along an arc or portion of a ring (i.e. spaced generally circumferentially about the arc), including where10062563567a plurality of such substantially linear rows of holes are provided as spaced-apart rings. In other words, the substantially linear row of holes can be a row of holes that generally track along a, typically curved, surface of the ore drive (i.e. corresponding to a shape of at least part of the ore drive). In an embodiment, said plurality of substantially linear rows of holes are spaced apart along the longitudinal direction. In an embodiment, said plurality of substantially linear rows of holes are spaced apart along the transverse direction. In an embodiment, said predetermined pattern includes a staggered arrangement. In an embodiment, said staggered arrangement includes a first substantially linear row of holes and a second substantially linear row of holes spaced apart from the first substantially linear row of holes. In an embodiment, the first substantially linear row of holes are spaced apart in the longitudinal direction from the second substantially linear row of holes. In an embodiment, the first substantially linear row of holes are spaced apart in the transverse direction from the second substantially linear row of holes. In an embodiment, said first substantially linear row of holes is substantially parallel with the second substantially linear row of holes. In an embodiment, further substantially linear rows of holes may be provided.

[0022] In an embodiment, said first substantially linear row of holes and said second substantially linear row of holes are angled with respect to each other. In an embodiment, one or both of said first substantially linear row of holes and said second substantially linear row of holes are angled towards the interface between the backfill material and the unexcavated stope. In an embodiment, one or both of said first substantially linear row of holes and said second substantially linear row of holes are angled away from the interface between the backfill material and the unexcavated stope. In an embodiment, said first substantially linear row of holes and said second substantially linear row of holes are arranged such that one or more distal ends of the holes of the first substantially linear row of holes are positioned closer to one or more distal ends of the holes of the second substantially linear row of holes and / or such that spacing between adjacent distal ends of the holes is selected to be sufficiently small that the holes collectively establish a substantially continuous blasting void at or near the interface between the backfill material and the unexcavated stope. Thus, in use, blasting is able to propagate between the holes without excessive unexcavated material remaining between adjacent holes (i.e. the unexcavated material is of little structural10062563568integrity so as to effectively create a continuous void). For example, said spacing between adjacent distal ends of the holes may be less than or equal to 1m for a hole of having a diameter of about 350mm. It will appreciated that hole diameter will in part dictate what spacing is suitable. In an embodiment, one or more holes of the first substantially linear row of holes and one or more holes of the second substantially linear row of holes are oriented such that the respective distal ends of the holes converge toward one another at a distal end of the holes. In other words, although the proximal end of the holes (i.e. the end closest to the drive, and opposite to the distal end of the hole) of the first substantially linear row of holes and the proximal ends of the holes of the second substantially linear row of holes may be laterally spaced apart, staggered, or otherwise separated when viewed from the proximal end, the holes are oriented such that the respective distal ends of the holes are located closer together. In an embodiment, the positions of the proximal ends of the holes are governed at least in part by the geometry and available dimensions of an ore drive from which the holes are drilled, and wherein one or more of the holes of the first substantially linear row of holes and / or the second substantially linear row of holes are drilled at an angle relative to the ore drive such that the respective distal ends of the holes of the first and second substantially linear rows of holes are positioned closer together than the respective proximal ends of those holes. To this end, the positioning of the distal ends can be determined by blast design requirements.

[0023] Reference to one or more holes being angled may include the one or more holes being formed with an orientation that differs from another hole and / or from a reference direction. In an embodiment, the orientation of a hole may include a variation in inclination (i.e. an up hole or down hole inclination and / or a forward or backward inclination relative to the interface between the backfill material and the unexcavated stope) and / or a variation in rotational or azimuthal orientation about the drilling axis, such that the hole is directed in a selected direction in three-dimensional space. It will be understood by a person skilled in the art that, by varying one or both of the inclination and the rotational or azimuthal orientation, the distal ends of the holes may be positioned at desired locations (including closer together) notwithstanding that the proximal ends of the holes may be positioned in locations governed at least in part by the geometry and available dimensions of the ore drive.10062563569

[0024] It will be understood that the staggered arrangement is one where the holes are not in a straight line but are offset or alternating. In an embodiment, said predetermined pattern can be such that the holes of the first substantially linear row of holes are placed away from a space between a pair of holes of the second substantially linear row of holes. In an embodiment, the predetermined pattern is between a 30-70° staggered pattern. In an embodiment, the predetermined pattern is between a 45° staggered pattern. In an embodiment, the predetermined pattern is between a 60° staggered pattern. In an embodiment, said predetermined pattern includes arranging the plurality of holes within a blasting void hole region disposed at the backfill material, near the interface between the backfill material and the unexcavated stope, wherein said blasting void hole region is generally elongate. Preferably, said blasting void hole region generally extends in the transverse direction. In an embodiment, said blasting void hole region generally extends in the longitudinal direction. In an embodiment, said blasting void hole region generally extends in both the longitudinal and transverse directions. In another embodiment, the predetermined pattern includes a generally circular, rectangular or square arrangement of holes adjacent to one another. It will appreciated by a person skilled in the art the that the arrangement of the plurality of holes will generally depend on mine site-specific parameters.

[0025] It will be understood that the plurality holes may be of any shape, including any combination of round, square, oblong, etc.

[0026] In an embodiment, at least one of the one or more blasting voids is a continuous or substantially continuous void having a width dimension greater than a depth dimension in cross-section, when viewed in plan. In other words, at least one of the one or more blasting voids is a continuous or substantially continuous void having, in plan-view cross-section, a width greater than a depth. By the continuous or substantially continuous void having a width dimension greater than a depth dimension, it is meant that this particular blasting void, be it defined by one hole or a plurality of holes, will have a width dimension greater than a depth dimension. In an embodiment, said at least one of the one or more blasting voids having a width dimension greater than a depth dimension is attributable at least in part to said generally elongate blasting void hole region. The width dimension may extend in the transverse direction, whilst the depth dimension may extend in the longitudinal direction. However, this may differ100625635610depending on the overall orientation of a given ore drive. In an embodiment, said at least one of the one or more blasting voids is a continuous or substantially continuous void having, in plan-view cross-section, a width greater than a depth along a substantial portion of the height thereof. In an embodiment, said at least one of the one or more blasting voids is a continuous or substantially continuous void having, in plan-view cross-section, a width greater than a depth along the whole height thereof. In an embodiment, the blasting void has a width to depth ratio of greater than about 1.1:1. In an embodiment, the blasting void has a width to depth ratio of between about 1.1:1 and about 75:1. In an embodiment, the blasting void has a width to depth ratio of at least about 1.1:1. In an embodiment, the blasting void has a width to depth ratio of at least about 2:1. In an embodiment, the blasting void has a width to depth ratio of at least about 5:1. In an embodiment, the blasting void has a width to depth ratio of at least about 10:1. The width to depth ratio can be calculated by dividing the width of the blasting void (including any material between the void holes in backfill which are of insignificant structural integrity so as to constitute a part of the blasting void) by the depth of the blasting void in plan (as distinct from the overall height of the blasting void). An advantage of creating a blasting void of greater width than depth is that the blasting void provides a wider target for blast holes to blast towards. Another advantage, particularly relative to conventional slot methods (such as raise bores and long holes rises), is it allows for the blasting void to generally correspond to the shape of the stope which is to be mined. In practice, the width to depth ratio (and therefore the dimension) of the final blasting void is in part dictated by mine-specific factors, such as the dimensions of the drive(s), the dimensions of the stope, the stope design, the firing sequence of blast holes, and other known mine engineering considerations. For example, the width to depth ratio may vary significantly between small width stopes and large width stopes, these factors dictated in part by site specific parameters such as drive placement, the presence of stub drives and the stope shape. The depth of the blasting void in backfill may also vary depending on how many rows of holes are drilled in the backfill to create the blasting void. It will also be appreciated that the width to depth ratio can vary along the height of the blasting void. This can occur due to the angles in which the holes in the backfill are created. For example, this can occur when the blasting void has been drilled in an arc or ‘fan’-type pattern from a drive where the100625635611width of the blasting void is narrower at its base (end closest to the drive in which it was drilled) and wider at its end (end furthest away from the drive in which it was drilled).

[0027] In an embodiment, at least one of the one or more blasting voids is configured to facilitate expansion of blasted material from the unexcavated stope towards the blasting void in a generally ‘forward’ direction. In an embodiment, each of the one or more blasting voids is configured to facilitate expansion of blasted material from the unexcavated stope towards the blasting void in a generally ‘forward’ direction. In an embodiment, the plurality of holes defining the one or more blasting voids are positioned forward of the blast holes in the unexcavated stope (i.e. formed in the backfill material on an opposite side of the interface from the blast holes) such that blasted material expands in the generally forward direction toward the blasting void. The generally forward direction is to be understood as the direction from the unexcavated stope to the backfill material. This is advantageous relative to known blast void formation methodologies that typically start by forming a central bore, followed by a series of blast holes around the central bore, with these blast holes fired in a specific sequence to ‘open up’ the blasting void by throwing the blasted material inwardly towards the central bore. In contrast, forming the one or more blasting voids in the backfill material, with blast holes formed in the hard rock material (near the backf il l / hard rock interface), the blasted material is blasted in a generally single, forward direction towards the one or more blasting voids formed in the backfill, thereby further opening up the one or more blasting voids. Put differently, the direction of a substantial portion of the blast energy is in this generally forward direction. Another advantage is that this method removes the requirement to have a large concentration of blast holes in a small area. This is particularly advantageous when poor ground conditions, common around stoping locations, are encountered that can result in blocked holes, lost drill rods and the need for re-excavation (e.g. re-drilling). All these issues can result in production delays.Another advantage is that this promotes the creation of a wider blasting void(s), which is particularly advantageous for the reasons previously mentioned. Further, in some embodiments, an added safety advantage is obtained by having the blasting void installed in the backfill material forward of the blast holes, for example because there is reduced personnel and / or equipment exposure beneath or above holes of larger diameter than the blast holes. In an up hole application, this can reduce risks associated100625635612with rocks falling out of raise bore holes and / or long hole rise reamer holes and striking personnel and / or equipment (e.g. charge rigs). In a down hole application, this can reduce hazards associated with exposure over large diameter holes, such as slip and trip risks, which are otherwise typically addressed by covering such holes.

[0028] In an embodiment, said plurality of holes are of greater diameter and / or width / depth relative to holes typically formed in long hole slot / rise methodologies. In an embodiment, one or more of the plurality of excavated holes have a diameter of less than or equal to 204 mm. In an embodiment, one or more of the plurality of excavated holes have a diameter of greater than 204 mm. In an embodiment, one or more of the plurality of holes have a diameter between 204 mm and about 1500 mm. In an embodiment, one or more of the plurality of holes have a diameter between about 350 mm and about 1000 mm. In an embodiment, one or more of the plurality of holes have a diameter between about 350 mm and about 500 mm. Advantageously, this embodiment represents a significant departure from known underground hard rock methodology associated with, for example, drill and blast mining, in which smaller diameter holes are excavated (e.g. relatively small reamer holes used in burn cut / long hole rise techniques). This in part is due to the inventions methodology of excavating holes in the backfill material, which enables holes of greater dimension to be excavated (e.g. drilled) than when excavating the hard rock material of the unmined ore.

[0029] In an embodiment, said excavating the plurality of holes includes excavating the plurality of holes using soft rock drilling methodology, for example rotary drilling with minimal percussion and aggressive-type cutting teeth, as opposed to hard rock drilling methodology, for example percussive drilling with button or cross bits. In an embodiment, said excavating the plurality of holes includes excavating the plurality of holes using soft rock equipment. In an embodiment, said excavating the plurality of holes includes drilling at least one of the plurality of the plurality of holes. In an embodiment, said drilling at least one of the plurality of holes includes drilling at least one of the plurality of holes using soft rock drill bit(s). In an embodiment, said excavating the plurality of holes includes drilling two or more of the plurality of holes. In an embodiment, said drilling two or more of the plurality of holes includes drilling two or more of the plurality of holes using soft rock drill bit(s). Preferably, said excavating100625635613includes drilling each of the plurality of holes. In an embodiment, said drilling each of the plurality of holes includes drilling each of the plurality of holes using soft rock drill bit(s).

[0030] In an embodiment, drilling of said holes is conducted by a suitable underground drilling machine. In an embodiment, drilling of said holes is conducted by a standard production drill rig. This represents a significant departure from known blasting void formation methodology as typically significantly more effort and equipment is used because of the conventional formation of the blasting void in the unexcavated stope. For example, there is no requirement for blasting void formation-specific blast holes, multiple firings, re-entry times after blasting, use of custom drilling and boring rigs such as raise bore / box hole rigs, etc. Further, in some embodiments, after the suitable underground drilling machine (e.g. production drill rig) is used to drill said holes, it can then be used to drill the required blast holes in the unexcavated stope.

[0031] By way of comparison, conventional mining methods for establishing blasting voids using a production drill rig typically involve drilling a predetermined pattern of holes known as a “burn cut” or long hole rise, including a plurality of blast holes (e.g. having diameters in a range of about 64 mm to about 102 mm, such as about 76 mm, 89 mm or 102 mm) disposed around one or more larger reamer holes (e.g. having diameters in a range of about 127 mm to about 204 mm, such as about 157 mm). In such conventional techniques, the long hole rise is typically formed by firing explosives to “blast out” the rise, thereby creating a blasting void for subsequent stope firings. In contrast, one or more embodiments disclosed herein involve utilising a standard production drill rig to drill the plurality of holes in the backfill material, to thereby define the blasting void, without the use of explosives. Further, it will be understood that the blasting void formed in accordance with one or more embodiments disclosed herein need not be a “rise” as that term is commonly understood in the art (i.e. a substantially vertical or inclined shaft extending between mine levels), and may instead be formed as a continuous or substantially continuous void that is wider than it is deep.

[0032] In an embodiment, said excavating the plurality of holes, such as by drilling, can be in the form of up holes (i.e. excavating up into the backfill material) or down holes (i.e. excavating down into the backfill material).100625635614

[0033] It will be understood that, in embodiments in which one or more of the holes are formed as down holes, operational considerations when drilling the down holes may include flushing of cuttings and selection of suitable air and / or water pressures and flow rates to assist clearing of cuttings from the hole, wherein factors such as hole depth and hole diameter may influence such requirements. In some embodiments, additional equipment, such as a compressor, may be used to facilitate removal of cuttings. In some embodiments, one or more of the down holes may be drilled to break through (e.g. into a lower ore drive) to assist clearing of cuttings, although this need not be the case. It will also be understood that in embodiments where one or more of the down holes do not break through, water, cuttings, or a mix of both may remain in the hole after drilling, and that such a hole may still constitute, or contribute to, a blasting void for stoping operations.

[0034] In an embodiment, said excavating the plurality of holes includes jetting out material using waterjets to form at least one, preferably each, of said plurality of holes. In an embodiment, said excavating the plurality of holes includes jetting out material using waterjets to form said one or more blasting voids.

[0035] In an embodiment, said excavating the plurality of holes may be conducted in a single pass, i.e. a series of holes excavated in a single hole forming sequence. In an alternative embodiment, said excavating the plurality of holes may be conducted in multiple passes. For example, the plurality of holes may be separately reamed out in an additional pass to increase the diameters of those holes relative to their initial excavated diameter.

[0036] In an embodiment, said one or more blasting voids is created without the use of explosives. There are several advantages with being able to create the one or more blasting voids without the use of explosives. One advantage is that there is reduced damage to the unexcavated stope, including any blast holes already formed in the unexcavated stope. Another advantage is that less equipment is required. For example, equipment such as charge rigs and transport equipment for the explosives is not required. There is also significant saving in consumable items, such as the explosives and detonators, blast bags, hole liners and bottlebrushes. Another advantage is that blasting in the backfill can be relatively inefficient as certain types of backfill (e.g.100625635615flowable backfills, cemented rock fill, etc) can absorb energy from a blast, unlike the more brittle hard rock material that would typically shatter or fragment.

[0037] In an embodiment, said method includes, before backfilling an open stope void, surveying the open stope void in order to determine at least one characteristic of the rock face of the unexcavated stope, wherein the rock face will be at the interface between the backfill material and the unexcavated stope after backfilling the open stope. In an embodiment said at least one characteristic can include one or more of location of the rock face, contour of the rock face, condition of the hanging wall, condition of the foot wall, and condition of the brow. An advantage of conducting said surveying is that it enables better planning for the excavation activities associated with excavating the plurality of holes. This can include an improved understanding of how deep a particular hole in the backfill material can be before encountering the rock face, which is often an uneven, jagged surface.

[0038] In an embodiment, said method includes conducting survey operations, including surveying one or more blast holes, to assist with planning drilling and blasting activities associated with mining the unexcavated stope. For example, survey “pick-ups” of one or more blast holes in a last production ring (or last ring) of blast holes in a stope that has been mined can assist in determining the condition and / or location of a final rock face for a next stope to be mined (i.e. the rock face that will define, at least in part, the interface between the backfill material and the unexcavated stope). This survey data can assist in determining whether a variation in drill and blast design is required prior to firing the stope, for example inclusion of additional blast holes.

[0039] In an embodiment, said plurality of holes together define a single blasting void. In another embodiment, said plurality of holes define a plurality of blasting voids.

[0040] Advantageously, the present invention provides an improved method of forming one or more blasting voids when mining underground. Unlike known prior art methods, most of which involve formation of the blasting void in the hard rock material of an unexcavated stope (having a compressive strength in the order of about 50-250 MPa for example), the formation of a blasting void in the backfill material (having a compressive strength in the order of about 0.5-10 MPa for example) provides substantial advantages. One advantage is that the one or more blasting voids can be created using standard100625635616mine production drilling rigs, rather than the more specialised hard rock-type equipment and methodology (e.g. hard-rock drills, bits, cutters, specific sequences, interactions and mine operations typically required to establish the blasting void). This enables the one or more blasting voids to be established in significantly less time than would typically be the case using conventional blasting void formation methodology, such as drill and blast (i.e. bum cut), drilled / bored rise (i.e. raise bore), and box hole processes. This has significant benefits to a particular mine in terms of scheduling, production equipment availability and cost of additional equipment and contractors.

[0041] Another advantage of the present invention is the reduction in mine cycle time given the reduced time in forming the one or more blasting voids and therefore the reduction in time to carry out a typical ore recovery and production process. Creating the blasting void is known as being a costly and time intensive part of the ore recovery and production process, and therefore simplifying this stage of the process is greatly beneficial to the mine.

[0042] A further advantage of the present invention is the potential for increase in production as a function of a reduction in the overall stope production cycle.

[0043] In a second aspect, the present invention provides a method of mining an unexcavated stope, the method including: creating one or more blasting voids by the method of the first aspect; creating a plurality of blast holes in the unexcavated stope near the interface between the backfill material and the unexcavated stope; loading the plurality of blast holes with explosives and blasting towards the one or more blasting voids previously established in the backfill material to form an open stope; and removing broken ore from the open stope.

[0044] It will be understood that by ‘near’ in reference to creating the plurality of blast holes in the unexcavated stope near the interface between the backfill material and the unexcavated stope, it is meant that the plurality of blast holes are arranged such that they are within a suitable distance of the one or more blasting voids so that the blast can propagate through distance burden disposed between the plurality of blast holes and the one or more blasting voids. In other words, the plurality of blast holes are arranged at a suitable distance to the interface between the backfill material and the unexcavated stope such that the blast can propagate through to the one or more100625635617blasting voids. A person skilled in the art will appreciate that the precise positioning of the plurality of blast holes can be different from mine to mine, as well as different for different ore bodies. Other factors will be the size, shape and arrangement of the plurality of blast holes, as well as the size of the one or more blasting voids.

[0045] In an embodiment, the method includes backfilling the open stope with backfill material. In an embodiment, the method includes allowing the backfill material to cure. In an embodiment, the method includes, after said backfilling, repeating the steps of: creating one or more blasting voids in the backfill material near an interface between the backfill material and a next unexcavated stope to mine, creating a plurality of blast holes in the remaining unexcavated stope near the interface between the backfill material and the remaining unexcavated stope, loading the plurality of blast holes with explosives and blasting towards the one or more blasting voids just established in the backfill material to form an open stope, and removing broken ore from the open stope. In an embodiment, said repeating the steps continues until the full length of the ore body has been mined.

[0046] In an embodiment, the method further includes developing an upper ore drive and a lower ore drive through respective mining levels along a strike of the ore body, wherein the one or more blasting voids extend from one of the upper ore drive and lower ore drive towards the other of the upper ore drive and lower ore drive. In an embodiment, the upper ore drive and the lower ore drive are developed before said creating the one or more blasting voids. In an embodiment, the one or more blasting voids have a height between about 80% and about 100% of a length between the upper ore drive and the lower ore drive. In an embodiment, the one or more blasting voids have a height between about 90% and about 100% of a length between the upper ore drive and the lower ore drive. In an embodiment, the one or more blasting voids have a height substantially corresponding to a length between the upper ore drive and the lower ore drive. It will be understood that the one or more blasting voids are configured to have a height that meets the engineering requirements to facilitate successful blasting of the stope.

[0047] In an alternative embodiment, the method includes developing an ore drive before said creating the one or more blasting voids, wherein the one or more blasting100625635618voids extend from the ore drive generally upwardly through the ore body. Thus, in this embodiment, there is no need for separate upper and lower drives, with instead a single drive (effectively similar to the lower drive of the earlier embodiment) provided.

[0048] In an embodiment, said creating the plurality of blast holes in the unexcavated stope near to the interface between the backfill material and the unexcavated stope includes creating the plurality of blast holes near to the one or more blasting voids. In other words, the plurality of blast holes are created in a nearby region to the one or more blasting voids. In an embodiment, the plurality of blast holes are arranged such that one or more of the plurality of holes are within about 0.5 m to 5 m of the interface between the backfill material and an unexcavated stope.

[0049] In an embodiment, said creating the plurality of blast holes includes excavating the plurality of blast holes. In an embodiment, said excavating the plurality of blast holes includes drilling the plurality of blast holes. In an embodiment, drilling of said plurality of blast holes is conducted by a suitable underground drilling machine. In an embodiment, drilling of said plurality of blast holes is conducted by a standard production drill rig. Preferably, said plurality of blast holes and said one or more blasting voids are created using the same underground drilling machine (e.g. the standard production drill rig). Advantageously, using the same underground drilling machine to create the one or more blasting voids and the plurality of blast holes provides significant time and cost savings for a mine.

[0050] In an embodiment, said excavating the plurality of blast holes includes jetting out material using waterjets. In an embodiment, said excavating the plurality of holes includes jetting out material using waterjets to form said one or more blasting voids.

[0051] In an embodiment, said creating the plurality of blast holes includes excavating said plurality of blast holes in a predetermined pattern in the unexcavated stope. In an embodiment, said predetermined pattern is configured such that, when the plurality of blast holes are fired, the blasted material is thrown towards the one or more blasting voids in a generally ‘forward’ direction. For example, said one or more blasting voids and said plurality of blast holes may be arranged such that when the blast holes are fired, said blasting towards the one or more blasting voids involves expansion of blasted material towards the one or more blasting voids in the generally forward direction. As100625635619mentioned previously, the generally forward direction is to be understood as the direction from the unexcavated stope to the backfill material. Thus, said plurality of blast holes may be formed rearward of the holes forming the blasting void(s). This is advantageous relative to known blast void formation methodologies that typically start by forming a central bore, followed by a series of blast holes around the central bore, with these blast holes fired in a specific sequence to ‘open up’ the blasting void by throwing the blasted material inwardly towards the central bore. In contrast, forming the one or more blasting voids in the backfill material, with blast holes formed in the hard rock material (near the backf il l / hard rock interface), the blasted material is blasted in a generally single, forward direction towards the one or more blasting voids formed in the backfill, thereby further opening up the one or more blasting voids. Put differently, the direction of a substantial portion of the blast energy is in this generally forward direction. Another advantage is that this method removes the requirement to have a large concentration of blast holes in a small area. This is particularly advantageous when poor ground conditions, common around stoping locations, are encountered that can result in blocked holes, lost drill rods and the need for re-excavation (e.g. re-drilling). All these issues can result in production delays. Another advantage is that this promotes the creation of a wider blasting void(s), which is particularly advantageous for the reasons previously mentioned. There are also safety advantages as previously described.

[0052] In an embodiment, said predetermined pattern of the plurality of blast holes includes a plurality of longitudinally spaced arcs (also known as production rings), wherein each arc includes a series of blast holes of the plurality of blast holes spaced generally circumferentially about the respective arc. It will be understood that said arcs may not necessarily be precisely curved shaped. In practice, said arcs will typically correspond to a shape of at least part of a particular ore drive. For example, said arc may correspond in shape to one of an upper or lower side of a particular ore drive, possibly in addition to two sides of the particular ore drive (depending on the direction the blast holes are being formed in). Put differently, the arc may be defined by one of an upper or lower side, as well as the left and right side of the particular ore drive when viewed longitudinally. In an embodiment, said blasting may include blasting each of the plurality of longitudinally spaced arcs in a predetermined sequence. For example, the100625635620predetermined sequence may include first firing the blast holes of a first arc, which is closest to the interface between the backfill material and the unexcavated stope, followed by the firing the blast holes of a second arc, and so on. A person skilled in the art will also appreciate that blast holes within a particular arc will themselves also typically be blasted in a predetermined sequence. It will be appreciated that other patterns for the plurality of blast holes known in the industry may be utilised. For example, a ‘dice 5’ pattern for the plurality of blast holes may be used.

[0053] In an embodiment, at least one of, and optionally each of, the plurality of blast holes are oriented substantially vertically. In another embodiment, at least one of, and optionally each of, the plurality of blast holes are oriented substantially towards the one or more blasting voids. It will be understood that the desired orientation of the plurality of blast holes may vary depending on the particular application.

[0054] In an embodiment, the method may include reaming one or more of said plurality of blast holes to increase the diameter (or depth / width if not round) thereof. Advantageously, these ‘reamer holes’ can be useful in certain applications where the unexcavated stope near the interface between the backfill material and the unexcavated stope includes a section of increased burden (where the initial blast hole(s) is deemed to be insufficient to achieve the desired blast outcome).

[0055] In an embodiment, the method further includes processing the broken ore, e.g. to extract metal and / or mineral from the ore.

[0056] It will be appreciated that features disclosed with respect to the first aspect of the invention are also applicable with respect to the second aspect of the invention, including different combinations of features disclosed.

[0057] In a third aspect, the present invention provides a drill bit for use in the method of the first or second aspects, said drill bit used for creating the plurality of holes extending into the backfill material that define the one or more blasting voids.

[0058] In an embodiment, said drill bit is of greater diameter than drill bits used in conventional long hole slot / rise methodologies.100625635621

[0059] In an embodiment, said drill bit is a non-typical hard rock bit (e.g. not a typical button bit). In an embodiment, said drill bit is a soft rock bit.

[0060] In an embodiment, said drill bit has a diameter greater than 204 mm. In an embodiment, said drill bit has a diameter between 204 mm and about 1500 mm. In an embodiment, said drill bit has a diameter between about 350 mm and about 1000 mm. In an embodiment, said drill bit has a diameter between about 350 mm and about 500 mm. Advantageously, this embodiment represents a significant departure from known underground hard rock drill bits used to form blasting voids in conventional mining methodologies, for example, drill and blast mining, in which smaller diameter holes are drilled (e.g. relatively small reamer holes used in burn cut / long hole rise techniques). This in part is due to the invention’s methodology of excavating holes in the backfill material, which enables holes of greater dimension to be drilled than when excavating the hard rock material of the unmined ore, thus enabling larger drill bits to be used.

[0061] In an embodiment, said drill bit has a diameter less than or equal 204 mm.

[0062] It will be appreciated that features disclosed with respect to the first and second aspects of the invention are also applicable with respect to the third aspect of the invention, including different combinations of features disclosed.

[0063] In a fourth aspect, the present invention provides a method of creating a blasting void during underground mining, said blasting void configured to allow expansion of blasted material during a stope firing, the method including: before backfilling an open stope with a backfill material, deploying a removable or partially removable plug into the open stope, wherein said plug is disposed near a wall or face of an unexcavated stope and extends a substantial portion of a length of the wall or face; backfilling the open stope with the backfill material, thereby setting the plug in place near the wall or face of the unexcavated stope; and removing all or a portion of the plug to thereby form said blasting void.

[0064] In an embodiment, the removable or partially removable plug is a dissolvable or partially dissolvable plug. In an embodiment, the removable or partially removable plug is an excavatable plug.100625635622

[0065] In an embodiment, said removing all or a portion of the plug to form the blasting void includes dissolving or partially dissolving the plug.

[0066] It will be understood that by ‘near’ in reference to the plug being disposed near the wall or face of the unexcavated stope, it is meant that the plug is arranged such that the blasting void that is to be formed therefrom is within a suitable distance of the blast holes so that the blast can propagate through burden disposed between the blast holes and the blasting void. In other words, the plug is arranged at a suitable distance to an interface between the backfill material and the wall or face of the unexcavated stope such that the blast can propagate through to the blasting void that is formed by excavating all or a portion of the plug. A person skilled in the art will appreciate that the precise positioning of the plug with respect to the unexcavated stope can be different from mine to mine, as well as different for different ore bodies. Other factors will be the size of plug (which relates to the size of the blasting void), as well as the size, shape and arrangement of the blast holes in the unexcavated stope.

[0067] In an embodiment, said plug is arranged to generally be aligned with said wall or face of the unexcavated stope (e.g. aligned with the length of the wall or face of the unexcavated stope). It will be understood that the wall or face of the unexcavated stope may not typically be substantially vertical, but could instead be angled, oriented closer to horizontal, etc. In other words, the length of the wall or face of the unexcavated stope may be oriented at an angle to the vertical or oriented closer to horizontal.

[0068] In an embodiment, said plug extends at least 60% of the length of the wall or face. In an embodiment, said plug extends at least 70% of the length of the wall or face. In an embodiment, said plug extends at least 80% of the length of the wall or face. In an embodiment, said plug extends at least 90% of the length of the wall or face. In an embodiment, said plug extends at least 95% of the length of the wall or face. In an embodiment, said plug extends the full length, or substantially the full length, of the wall or face.

[0069] In an embodiment, said plug is an elongate structure. In an embodiment, said plug is substantially cylindrical in shape. However, said plug may also be of different shape depending on the desired characteristics of the blasting void for a given100625635623application. In an embodiment, a cross-sectional shape of the plug is one of substantially circular, substantially rectangular, substantially oblong, etc.

[0070] In an embodiment, backfill material is a flowable backfill material. In an embodiment, the flowable backfill material includes a paste fill, mine tailings, concrete or similar. In another embodiment, the backfill material is a non-flowable backfill material. In an embodiment, the non-flowable backfill material includes rock (e.g. waste rock, crushed rock, etc.), crushed aggregate, cemented rock fill, or similar.

[0071] In an embodiment, the excavatable plug includes an excavatable material and a casing, wherein said excavatable material is substantially contained within a volume defined by the casing. Preferably, the casing is hollow. In an embodiment, the casing is of substantially closed-shape type. In other words, said volume may be fully or substantially surrounded by the casing. For example, the casing may be substantially tubular-shaped. In another embodiment, the casing is of substantially open-shape type, wherein said volume is surrounded by a combination of the casing and the wall or face of the unexcavated stope. For example, the casing may be substantially channelshaped.

[0072] In an embodiment, said deploying a removable or partially removable plug into the open stope includes deploying the casing into the open stope, wherein said casing is disposed near the wall or face of the unexcavated stope and arranged to generally be aligned with said wall or face of the unexcavated stope. In an embodiment, said deploying a removable or partially removable plug into the open stope includes deploying the casing into the open stope, wherein said casing is disposed near the wall or face of the unexcavated stope and arranged to generally abut said wall or face of the unexcavated stope. In an embodiment, the method may include forming a notch in the wall or face of the unexcavated stope, wherein said deploying a removable or partially removable plug into the open stope includes positioning the casing in the notch.

[0073] In an embodiment, the method further includes, after deploying said casing, filling said casing with the excavatable material, thereby fully forming the deployed excavatable plug. In an alternative embodiment, the excavatable material and the casing are pre-formed or pre-cast to form the excavatable plug.100625635624

[0074] In an embodiment, said excavating all or a portion of the plug includes excavating at least a portion of the excavatable material. In an embodiment, said excavating all or a portion of the plug includes excavating a substantial portion of the excavatable material. In an embodiment, said excavating all or a portion of the plug includes excavating all the excavatable material.

[0075] In an embodiment, said excavating at least a portion of the excavatable material includes drilling out said at least a portion of the excavatable material. In an embodiment, said excavating a substantial portion of the excavatable material includes drilling out said substantial portion of the excavatable material. In an embodiment, said excavating all of the excavatable material includes drilling out said all of the excavatable material. In an embodiment, said excavating at least a portion of the excavatable material is done using the drill bit of the third aspect of the invention. In another embodiment, said excavating at least a portion of the excavatable material includes jetting out the at least a portion of excavatable material using waterjets. In an embodiment, said excavating a substantial portion of the excavatable material includes jetting out said substantial portion of the excavatable material using waterjets. In an embodiment, said excavating all of the excavatable material includes jetting out said all of the excavatable material using waterjets.

[0076] In another embodiment, said excavating all or a portion of the plug includes excavating the excavatable material and the casing. In an embodiment, said excavating the excavatable material and the casing includes drilling out the excavatable material and the casing. In another embodiment, said excavating the excavatable material and the casing includes jetting out the excavatable material and the casing using waterjets.

[0077] In an embodiment, drilling out the excavatable material is conducted by a suitable underground drilling machine. In an embodiment, drilling out the excavatable material is conducted by a standard production drill rig.

[0078] Preferably, the excavatable material is of lower compressive strength than the unexcavated stope. In an embodiment, the excavatable material may have a compressive strength of less than 10 MPa. In an embodiment, the excavatable material may have a compressive strength of less than 5 MPa. In an embodiment, the excavatable material may have a compressive strength of less than 3 MPa. In an100625635625embodiment, the excavatable material may have a compressive strength between about 0.5 MPa and 3 MPa. In an embodiment, said excavatable material is formed of one or more of: mine tailings (wet or dry), sand, gravel, paste fill, cardboard, polystyrene, polymers, foams, or other suitable excavatable material (e.g. a suitable natural or engineered material with properties to meet the desired function).

[0079] In an embodiment, the casing is configured to withstand internal pressure imparted by the excavatable material onto an interior of the casing, such that the casing does not rupture, crumple or otherwise be sufficiently damaged to impact its functionality, particularly when filling said casing with the excavatable material. In an embodiment, the excavatable plug includes an inner lining configured to be positioned between the casing and the excavatable material, wherein the inner lining is configured to prevent the excavatable material from leaking out of the casing.

[0080] In an embodiment, the excavatable plug is configured to withstand external pressure imparted by the backfill material onto an exterior of the plug, such that the plug does not rupture, crumple or otherwise be sufficiently damaged to impact its functionality, particularly when backfilling the open stope with the backfill material. In an embodiment, the casing is configured to withstand external pressure imparted by the backfill material onto an exterior of the casing, such that the casing does not rupture, crumple or otherwise be sufficiently damaged, particularly when backfilling the open stope with the backfill material. In another embodiment, the excavatable plug formed of a combination of the casing and the excavatable material is configured to withstand external pressure imparted by the backfill material onto an exterior of the plug, such that the plug does not rupture, crumple or otherwise be sufficiently damaged, particularly when backfilling the open stope with the backfill material. In an embodiment, the excavatable plug includes bracing structure disposed in an interior thereof to provide resistance against said external pressure. In one example, the bracing structure includes internal struts configured to enhance the integrity of the casing against said external pressure.

[0081] In an embodiment where the excavatable material is to be excavated with the casing remaining set in the backfill material, said casing is configured to enable blast energy to propagate through the casing towards the blasting void.100625635626

[0082] In an embodiment, the excavatable plug is secured to the wall or face of the unexcavated stope prior to said backfilling the open stope with the backfill material.

[0083] In an embodiment, the blasting void is configured to facilitate expansion of blasted material from the unexcavated stope towards the blasting void in a generally ‘forward’ direction. The generally forward direction is to be understood as the direction from the unexcavated stope to the backfill material.

[0084] In an embodiment, said casing is a unitary element.

[0085] In another embodiment, said casing includes a plurality of casing elements configured to be interconnected with one another, preferably in an end-to-end relationship, to form a continuous, substantially rigid casing assembly. In an embodiment, the substantially rigid casing assembly is disposed near the wall or face of the unexcavated stope prior to said backfilling the open stope. Advantageously, this embodiment provides an elongate, substantially rigid casing assembly comprised of a plurality of casing elements assembled or interconnected in a substantially fixed or rigid manner. The casing elements are therefore in the form of modular elements in the sense that a desired or selected number of casing elements can be assembled or connected together to produce the substantially rigid casing assembly in a desired size or length. In this way, a user has flexibility in selecting or determining an overall size or length of the casing assembly for a given mine or ore body to be excavated. This also provides for greater accuracy and reliability in positioning of the casing elements near the wall or face of the unexcavated stope, which, in turn, is relevant for achieving a desired position of the blasting void and, thus, an optimal result from firing of the charges set in the nearby blast holes. From a practical perspective, managing the transport and handling of the casing elements in the underground mine is also improved relative to provision of a casing of unitary form.

[0086] In an embodiment, each of the plurality of casing elements is generally elongate and the plurality of casing elements are rigidly interconnected with one another via one or more connector elements, such as bolts, dowels, cables, or a combination of them. For example, the plurality of casing elements may be bolted together in end-to-end relationship. Alternatively, they may be drawn together by one or more cables under tension extending along or through a length of the casing elements. In this regard, the100625635627plurality of casing elements may be preassembled or interconnected with one another in the fixed end-to-end relationship prior to their deployment near the wall or face of the unexcavated stope. Alternatively, they may be progressively assembled or interconnected with one another in the fixed end to-end relationship during their deployment near the wall or face of the unexcavated stope.

[0087] It will be appreciated that the “end-to-end relationship” of the plurality of casing elements assembled to form the substantially rigid casing assembly is not limited to an arrangement of abutting end faces of the casing elements (e.g., in a butt joint) but also includes an arrangement of overlapping end surfaces or end regions of the casing elements (e.g., in a lap joint). Thus, it will be appreciated that the plurality of casing elements may be arranged telescopically with respect to one another and / or may be rigidly interconnected with one another with a degree of overlap in an axial direction or, alternatively, in a lateral or side-by-side direction.

[0088] In an embodiment, each of the casing elements includes one or more connector elements, such as complementary or mating connectors, at opposite ends thereof to assist positioning and / or alignment of the casing elements in the end-to-end relationship with one another to form the continuous and substantially rigid casing assembly.

[0089] In an embodiment, each of the casing elements are of an open shape-type. For example, each of the casing elements include or define a cavity and, when the plurality of casing elements are interconnected with one another in a fixed end-to-end relationship to form a continuous, substantially rigid casing assembly, the cavities of the respective casing elements combine or align to define the volume to be filled with the excavatable material. In an embodiment, said open shape-type includes a tubular section.

[0090] In an embodiment, each, or at least one, of the plurality of casing elements is formed as, or comprises, a channel-shaped element that defines a cavity between sides of the channel shape. For example, the channel-shaped casing elements may have a generally U-shaped or V-shaped cross-sectional profile. The cavities of each of the channel-shaped casing elements combine, when the casing elements are interconnected or assembled, to define or to form the volume of the casing assembly. In one example, each casing element may have a generally U-shaped cross-sectional100625635628profile, e.g., forming a generally rectangular channel shape having side walls that extend approximately perpendicularly from a flat base. A square or rectangular cross-sectional profile is especially preferred due to its capacity to maximise the width for a given volume near the wall or face of the unexcavated stope. A height of the side walls and a width of the base of the rectangular channel shape may be, e.g., in a range of about 500 mm to 1500 mm, and can be whatever dimensions are appropriate for the specific drilling and blast activities concerned. The channel-shaped casing elements are particularly suitable for pre-cast plugs, i.e. where the cavity is filled with the excavatable material.

[0091] In an embodiment, said deploying the excavatable plug includes connecting a plurality of casing elements together to form said casing. In an embodiment, the method further includes filling said casing assembly with the excavatable material, thereby fully forming the deployed excavatable plug.

[0092] In an embodiment, each of the plurality of casing elements is comprised of a robust material and preferably a durable, high-density material, such as steel or reinforced concrete, which will be capable of withstanding high loads in use. In this regard, for example, when a backfill material such as a waste rock or similar is used, the plurality of casing elements forming the casing assembly will typically be subject to impact loading and abrasion during the backfilling process and they should therefore be sufficiently strong and durable to readily withstand the loading conditions. It will be appreciated, however, that the plurality of casing elements may also be comprised of a robust and durable, light-weight material, such as an engineering plastic, especially when the loading expected during backfilling may be lower, as is the case when backfilling with a flowable backfill material such as mine tailings or paste fill pumped into the open stope. Examples of engineering plastics include polyamide (PA, Nylon), polyethylene (PE, HDPE), polyvinylchloride (PVC), polycarbonate (PC), and polyurethane (Pll). It will also be appreciated that composite materials, such as fibre-reinforced polymers, may be suitable in certain applications.

[0093] In an embodiment, said excavatable plug includes a plurality of plug elements configured to be interconnected with one another, preferably in an end-to-end relationship. For example, each plug element may include both a casing and100625635629excavatable material so that no subsequent filling of excavatable material step is required when deploying the plug.

[0094] In an embodiment, said method includes, before backfilling the open stope and before deploying the excavatable plug into the open stope, surveying the open stope in order to determine at least one characteristic of the wall or face of the unexcavated stope, which will be at an interface between the backfill material and the unexcavated stope. In an embodiment said at least one characteristic can include one or more of location of the wall or face, contour of the rock face, condition of the hanging wall, condition of the foot wall, and condition of the brow.

[0095] In an embodiment, the casing includes a closed lower end to prevent leakage of the excavatable material when filling the casing with the excavatable material. In another embodiment, the casing includes an open lower end configured to engage with a mine floor, whereby the mine floor closes the casing to prevent leakage of the excavatable material when filling the casing with the excavatable material.

[0096] In an embodiment, the method includes before backfilling the open stope with the backfill material, deploying a second excavatable plug, spaced away from the first excavatable plug, into the open stope, wherein said second plug is disposed near the wall or face of the unexcavated stope and extends a substantial portion of the length of the wall or face; backfilling the open stope with the backfill material, thereby setting the first and second plugs in place near the wall or face of the unexcavated stope; and excavating all or a portion of the first and second plugs to thereby form first and second blasting voids. It will be appreciated that multiple blasting voids may be created using this method.

[0097] It will be understood that some of the features referred to above in relation to the excavatable plug may also apply to the removable or partially removable plug (i.e. in relation to features not specific to excavation).

[0098] Advantageously, the present invention provides an improved method of forming a blasting void when mining underground. Unlike known prior art methods, most of which involve formation of the blasting void in the hard rock material of an unexcavated stope (having a compressive strength in the order of about 50-250 MPa), the formation100625635630of a blasting void in the backfill material provides substantial advantages. One advantage is that the blasting void can be created using standard mine production drilling rigs, rather than the more specialised hard rock-type equipment and methodology (e.g. hard-rock drills, bits, cutters, specific sequences, interactions and mine operations typically required to establish the blasting void). This enables the blasting void to be established in significantly less time than would typically be the case using conventional blasting void formation methodology, such as drill and blast (i.e. burn cut), drilled / bored rise (i.e. raise bore), and box hole processes. This has significant benefits to a particular mine in terms of scheduling, production equipment availability and cost of additional equipment and contractors.

[0099] Another advantage of the present invention is the reduction in mine cycle time given the reduced time in forming the blasting void and therefore the reduction in time to carry out a typical ore recovery process. Creating the blasting void is known as being a costly and time intensive part of the ore recovery process, and therefore simplifying this stage of the process is greatly beneficial to the mine.

[0100] A further advantage of the present invention is the potential for increase in production as a function of a reduction in the overall stope production cycle given the excavatable plug is set in the backfill material and can be relatively easily excavated at a later time.

[0101] It will be appreciated that features disclosed with respect to the first, second or third aspects of the invention are also applicable with respect to the fourth aspect of the invention, including different combinations of features disclosed.

[0102] In a fifth aspect, the present invention provides a method of mining an unexcavated stope, the method including: creating a blasting void by the method of the fourth aspect; creating a plurality of blast holes in the unexcavated stope near an interface between the backfill material and the unexcavated stope; loading the plurality of blast holes with explosives and blasting towards the blasting void previously established in the backfill material to form an open stope; and removing broken ore from the open stope.100625635631

[0103] It will be understood that by ‘near’ in reference to creating the plurality of blast holes in the unexcavated stope near the interface between the backfill material and the unexcavated stope, it is meant that the plurality of blast holes are arranged such that they are within a suitable distance of the blasting void so that the blast can propagate through distance burden disposed between the plurality of blast holes and the blasting void. In other words, the plurality of blast holes are arranged at a suitable distance to the interface between the backfill material and the unexcavated stope such that the blast can propagate through to the blasting void. A person skilled in the art will appreciate that the precise positioning of the plurality of blast holes can be different from mine to mine, as well as different for different ore bodies. Other factors will be the size, shape and arrangement of the plurality of blast holes, as well as the size of the blasting void. To this end, the plurality of blast holes can be arranged such that they are within a suitable distance to the blasting void to ensure the blast can propagate through burden disposed between the blast holes and the blasting void and, as necessary, through the casing of the excavatable plug (if present).

[0104] In an embodiment, the method includes repeating the steps of: creating a blasting void by the method of the fourth aspect; creating a plurality of blast holes in a next unexcavated stope near an interface between the backfill material and the next unexcavated stope; loading the plurality of blast holes with explosives and blasting towards the blasting void just established in the backfill material to form an open stope; and removing broken ore from the open stope. In an embodiment, said repeating the steps continues until the full length of the ore body has been mined.

[0105] In an embodiment, said creating the plurality of blast holes in the unexcavated stope near the interface between the backfill material and the unexcavated stope includes creating the plurality of blast holes near to the blasting void. In other words, the plurality of blast holes are created in a nearby region to the blasting void.

[0106] In an embodiment, said creating the plurality of blast holes includes excavating the plurality of blast holes. In an embodiment, said excavating the plurality of blast holes includes drilling the plurality of blast holes. In an embodiment, drilling of said plurality of blast holes is conducted by a suitable underground drilling machine. In an embodiment, drilling of said plurality of blast holes is conducted by a standard production drill rig.100625635632Preferably, said plurality of blast holes and said blasting void are created using the same underground drilling machine (e.g. the standard production drill rig).Advantageously, using the same underground drilling machine to create the blasting void and the plurality of blast holes provides significant time and cost savings for a mine.

[0107] In an embodiment, said excavating the plurality of blast holes includes jetting out material using waterjets.

[0108] In an embodiment, said creating the plurality of blast holes includes excavating said plurality of blast holes in a predetermined pattern in the unexcavated stope. In an embodiment, said predetermined pattern is configured such that, when the plurality of blast holes are fired, the blasted material is thrown towards the blasting void in a generally ‘forward’ direction. For example, said blasting void and said plurality of blast holes may be arranged such that when the blast holes are fired, said blasting towards the blasting void involves expansion of blasted material towards the blasting void in the generally forward direction. As mentioned previously, the generally forward direction is to be understood as the direction from the unexcavated stope to the backfill material. Advantages of this feature are as previously mentioned.

[0109] In an embodiment, said predetermined pattern of the plurality of blast holes includes a plurality of longitudinally spaced arcs (also known as production rings), wherein each arc includes a series of blast holes of the plurality of blast holes spaced generally circumferentially about the respective arc. It will be understood that said arcs may not necessarily be precisely curved shaped. In practice, said arcs will typically correspond to a shape of at least part of a particular ore drive. For example, said arc may correspond in shape to one of an upper or lower side of a particular ore drive, possibly in addition to two sides of the particular ore drive (depending on the direction the blast holes are being formed in). Put differently, the arc may be defined by one of an upper or lower side, as well as the left and right side of the particular ore drive when viewed longitudinally. In an embodiment, said blasting may include blasting each of the plurality of longitudinally spaced arcs in a predetermined sequence. For example, the predetermined sequence may include first firing the blast holes of a first arc, which is closest to the interface between the backfill material and the unexcavated stope,100625635633followed by the firing the blast holes of a second arc, and so on. A person skilled in the art will also appreciate that blast holes within a particular arc will themselves also typically be blasted in a predetermined sequence. It will be appreciated that other patterns for the plurality of blast holes known in the industry may be utilised. For example, a ‘dice 5’ pattern for the plurality of blast holes may be used.

[0110] In an embodiment, at least one of, and optionally each of, the plurality of blast holes are oriented substantially vertically. In another embodiment, at least one of, and optionally each of, the plurality of blast holes are oriented substantially towards the blasting void. It will be understood that the desired orientation of the plurality of blast holes may vary depending on the particular application.

[0111] In an embodiment, the method may include reaming one or more of said plurality of blast holes to increase the diameter (or depth / width if not round) thereof.

[0112] In an embodiment, the method further includes processing the broken ore, e.g. to extract metal and / or mineral from the ore.

[0113] It will be appreciated that features disclosed with respect to the first, second, third or fourth aspects of the invention are also applicable with respect to the fifth aspect of the invention, including different combinations of features disclosed.

[0114] In a sixth aspect, the present invention provides a removable or partially removable plug for creating a blasting void during underground mining, said removable or partially removable plug configured to be disposed in an open stope near a wall or face of an unexcavated stope and set in place when said open stope is backfilled by a backfill material, wherein said blasting void is created when all or a portion of the plug is removed.

[0115] In an embodiment, the removable or partially removable plug is a dissolvable or partially dissolvable plug. In an embodiment, the removable or partially removable plug is an excavatable plug.

[0116] In an embodiment, said removing all ora portion of the plug to form the blasting void includes dissolving or partially dissolving the plug.100625635634

[0117] Preferably, the removable or partially removable plug is for creating a blasting void using the method of the fourth aspect.

[0118] It will be appreciated that features disclosed with respect to the first, second, third, fourth or fifth aspects of the invention are also applicable with respect to the sixth aspect of the invention, including different combinations of features disclosed.

[0119] In a seventh aspect, the present invention provides a method of creating a nonblasting void for underground mining, the method including: deploying a removable or partially removable plug into an open excavation; and removing all or a portion of the plug to thereby form said non-blasting void.

[0120] In an embodiment, the removable or partially removable plug is a dissolvable or partially dissolvable plug. In an embodiment, the removable or partially removable plug is an excavatable plug.

[0121] In an embodiment, said removing all or a portion of the plug to form the nonblasting void includes dissolving or partially dissolving the plug.

[0122] In an embodiment, said non-blasting void is a ventilation void (e.g. a vent shaft) configured to allow passage of air. In another embodiment, said non-blasting void is an ore pass.

[0123] In an embodiment, the removable or partially removable plug is configured to snugly fit within the open excavation such that no backfill material is required to retain the removable or partially removable plug within the open excavation.

[0124] In an embodiment, the removable or partially removable plug is narrower in dimension than the open excavation, thereby defining a gap between the removable or partially removable plug and the open excavation, wherein the method further includes backfilling the gap between the plug and the open excavation with a backfill material, thereby setting the plug in place within the open excavation. In an embodiment, said gap is an annular gap, and the backfill material fills the annular gap forming an annulus of backfill material.100625635635

[0125] In an embodiment, after said removing all or a portion of the plug, at least the annulus of backfill material remains, wherein the annulus of backfill material is configured to maintain the integrity of the non-blasting void.

[0126] In an embodiment, the method includes, before deploying the removable or partially removable plug, excavating to form the open excavation. In an embodiment, said excavating to form the open excavation includes drilling. In an embodiment, said excavating to form the open excavation includes jetting out material using waterjets.

[0127] In an embodiment, the method further includes, after removing all or a portion of the plug, installing bracing in the non-blasting void, wherein the bracing is configured to maintain the integrity of the non-blasting void. In an embodiment, said bracing includes a lining. In an embodiment, said lining is in the form of a casing. Preferably, the casing is formed of steel. However, the casing may be formed of other materials, including other metals, polymers, etc. In an embodiment, the bracing is secured to an interior of the non-blasting void. For example, the bracing may be secured (e.g. using a cement, fastening means, etc) to the interior of the non-blasting void. In an embodiment where the annulus of backfill material remains, the bracing may be secured to an interior of the annulus of backfill material (e.g. ‘grouting’ between the annulus of backfill material and the bracing).

[0128] The backfill material may be any one or more of the backfill materials previously described. In an embodiment, the backfill material may include cementitious products, foams or resins.

[0129] Advantageously, this method has significant advantages for a mine in terms of speed of implementation and enabling the non-blasting void to be stabilised / supported without putting mining workers into the non-blasting void to insert stabilisers, such as rock bolts. Over time, the non-blasting voids deteriorate, and thus require excessive rock bolting, shotcrete, and / or other stabilisers to prevent blockage or closure of the non-blasting void. The need to employ these stabilising techniques results in greater cost and wasted time for a mine. The present method addresses this issue, at least in part, by providing a relatively simple to remove / excavate plug, but also allows for maintaining the integrity of the non-blasting void for a relatively extended period of time (relative to not stabilising the non-blasting void).100625635636

[0130] It will be appreciated that features disclosed with respect to the first, second, third, fourth, fifth or sixth aspects of the invention are also applicable with respect to the seventh aspect of the invention, including different combinations of features disclosed.

[0131] In an eighth aspect, the present invention provides a removable or partially removable plug for creating a non-blasting void during underground mining, said removable or partially removable plug configured to be disposed in an open excavation, wherein said non-blasting void is created when all or a portion of the plug is removed.

[0132] In an embodiment, the removable or partially removable plug is a dissolvable or partially dissolvable plug. In an embodiment, the removable or partially removable plug is an excavatable plug.

[0133] In an embodiment, said removing all or a portion of the plug to form the nonblasting void includes dissolving or partially dissolving the plug.

[0134] Preferably, the removable or partially removable plug is for creating a nonblasting void using the method of the seventh aspect.

[0135] It will be appreciated that features disclosed with respect to the first, second, third, fourth, fifth, sixth or seventh aspects of the invention are also applicable with respect to the eighth aspect of the invention, including different combinations of features disclosed.

[0136] In a ninth aspect, the present invention provides a method for creating a nonblasting void for underground mining, the method including: excavating, in a backfill material used to close an open excavation, a hole extending into the backfill material, said hole defining the non-blasting void.

[0137] In an embodiment, said non-blasting void is a ventilation void (e.g. a vent shaft) configured to allow passage of air. In another embodiment, said non-blasting void is an ore pass.

[0138] In an embodiment, said hole is surrounded by an annulus of remaining backfill material, wherein the annulus of remaining backfill material is configured to maintain the100625635637integrity of the non-blasting void for a relatively extended period of time (relative to not having the remaining backfill).

[0139] In an embodiment, said excavating the holes includes drilling. In an embodiment, said excavating the hole includes jetting out material using waterjets.

[0140] In an embodiment, the method further includes, after excavating the hole, installing bracing in the non-blasting void, wherein the bracing is configured to maintain the integrity of the non-blasting void. In an embodiment, said bracing includes a lining. In an embodiment, said lining is in the form of a casing. Preferably, the casing is formed of steel. However, the casing may be formed of other materials, including other metals, polymers, etc. In an embodiment, the bracing is secured to an interior of the nonblasting void. For example, the bracing may be secured (e.g. using a cement, fastening means, etc) to the interior of the non-blasting void. In an embodiment where the annulus of backfill material remains, the bracing may be secured to an interior of the annulus of backfill material (e.g. ‘grouting’ between the annulus of backfill material and the bracing).

[0141] It will be appreciated that features disclosed with respect to the first, second, third, fourth, fifth, sixth, seventh or eighth aspects of the invention are also applicable with respect to the ninth aspect of the invention, including different combinations of features disclosed.

[0142] In a tenth aspect, the present invention provides a method of processing ore that was recovered using the method of mining an unexcavated stope of the second or fifth aspect of the invention.

[0143] In an embodiment, said processing ore includes extracting metal and / or mineral from the ore.

[0144] It will be appreciated that features disclosed with respect to the first, second, third, fourth, fifth, sixth, seventh, eighth or ninth aspects of the invention are also applicable with respect to the tenth aspect of the invention, including different combinations of features disclosed.100625635638

[0145] As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps.

[0146] Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.Brief description of the drawings

[0147] Figure 1 is a schematic perspective view of a section through a stope illustrating blast holes drilled in the rock strata from a lower tunnel, drive, or work chamber towards an upper tunnel, drive, or work chamber;

[0148] Figure 2 is a schematic cross-sectional perspective view of a mine environment showing upper and lower drives, tunnels or work chambers and blasted ore being collected or “mucked out” at the lower level;

[0149] Figure 3a is a cross-sectional view of the technique used in drilling a blasting void in a similar manner to a “burn cut” or long hole winze;

[0150] Figure 3b is a cross-sectional view of blast holes drilled generally parallel to and spaced from a reamed hole, such as a raise bore;

[0151] Figure 4 is a schematic cross-sectional side view of a mine environment showing an ore body, a previously mined stope, and a back-filled region;

[0152] Figure 5 is a cross-sectional view of an unmined stope showing a schematic ore body extending between the upper and lower drives, tunnels, or work chambers;

[0153] Figure 6 is a schematic cross-sectional side view of a mine environment showing an ore body and a currently mined stope;

[0154] Figure 7 is a schematic cross-sectional side view of a mine environment showing an ore body, a previously mined stope with backfill;100625635639

[0155] Figure 8 is a schematic cross-sectional side view of a mine environment showing an ore body, a previously mined stope, and a backfilled region having a blasting void formed therein;

[0156] Figure 9 is a schematic cross-sectional side view of a mine environment showing an ore body with blast holes drilled therein, a previously mined stope, and a backfilled region having a blasting void formed therein;

[0157] Figure 10 is a photograph illustrating a suitable pattern of void holes in backfill material;

[0158] Figure 11 is an image showing the outcome of a trial employing a method of creating a blasting void in accordance with an embodiment;

[0159] Figure 12 is a schematic cross-sectional side view of a mine environment showing an ore body and a currently mined stope;

[0160] Figure 13 is a schematic cross-sectional side view of a mine environment showing an ore body, a previously mined stope, and a casing;

[0161] Figure 14 is a schematic cross-sectional side view of a mine environment showing an ore body, a previously mined stope, a casing, and a backfilled region;

[0162] Figure 15 is a schematic cross-sectional side view of a mine environment showing an ore body, a previously mined stope, a casing, and a backfilled region having a blasting void formed therein through the casing;

[0163] Figure 16 is a schematic cross-sectional side view of a mine environment showing an ore body with blast holes drilled therein, a previously mined stope, and a backfilled region having a blasting void formed therein through the casing;

[0164] Figures 17a-b are photographs of a suitable paste drill bit that can be utilised to create a blasting void in backfill material;

[0165] Figure 18 is a schematic cross-sectional plan view of a mine environment showing a shaft formed in surrounding hard rock;100625635640

[0166] Figure 19 is a schematic cross-sectional plan view of a mine environment showing a shaft formed in surrounding hard rock that has been filled with backfill material;

[0167] Figure 20 is a schematic cross-sectional plan view of a mine environment showing partial excavation of the backfill material from the shaft to form a non-blasting void;

[0168] Figure 21 is a schematic cross-sectional plan view of a mine environment showing the non-blasting void being supported by a lining;

[0169] Figure 22 is schematic cross-sectional side view of Figure 21 ;

[0170] Figure 23 is a schematic cross-sectional plan view of a mine environment showing a shaft formed in surrounding hard rock;

[0171] Figure 24 is a schematic cross-sectional plan view of a mine environment showing an excavatable plug deployed a shaft surrounded by hard rock;

[0172] Figure 25 is a schematic cross-sectional plan view of a mine environment showing the excavatable plug set into the shaft by backfill material;

[0173] Figure 26 is a schematic cross-sectional plan view of a mine environment showing excavation of the plug from the shaft to form a non-blasting void;

[0174] Figure 27 is a schematic cross-sectional plan view of a mine environment showing the non-blasting void being supported by a lining;

[0175] Figure 28 is a schematic cross-sectional side view of the mine environment shown in Figure 4 illustrating a step of a method of creating a blasting void;

[0176] Figure 29 is a schematic cross-sectional side view of the mine environment shown in Figure 28 illustrating another step of the method of creating a blasting void;

[0177] Figure 30 is a schematic cross-sectional side view of the mine environment shown in Figure 29 illustrating another step of the method of creating a blasting void;100625635641

[0178] Figure 31 is a schematic perspective view of part of an apparatus for positioning casing elements and / or a casing with respect to a wall or face of an unmined stope;

[0179] Figure 32 is a schematic cross-sectional end view of a casing element and the apparatus for positioning the casing element shown in Figure 31;

[0180] Figure 33 is a schematic cross-sectional side view of the mine environment shown in Figure 30 illustrating another step of the method of creating a blasting void;

[0181] Figure 34 is a schematic cross-sectional side view of the mine environment shown in Figure 33 illustrating another step of the method of creating a blasting void;

[0182] Figure 35 is a schematic cross-sectional side view of the mine environment shown in Figure 34 illustrating another step of the method of creating a blasting void;

[0183] Figure 36 is a schematic front view of a wall or face of the unmined stope showing the ore body and the casing schematically extending between upper and lower drives or tunnels at a desired angle;

[0184] Figure 37 is a schematic side view of a cradle of the positioning apparatus with the casing in the position shown in Figure 33;

[0185] Figure 38 is a schematic front view of the cradle of the positioning apparatus tilted at an angle to match an orientation of the ore body at a face of the stope;

[0186] Figure 39 is schematic side view of the cradle of the positioning apparatus with the barrier member moved to the position shown in Figure 34;

[0187] Figure 40 is a plan view of a drive having a plurality of longitudinally spaced removable (or partially removable) plugs disposed in an ore body;

[0188] Figure 41 is a schematic top view of a suitable pattern of void holes in backfill material;

[0189] Figure 42 is a schematic top view of another suitable pattern of void holes in backfill material, the upper part of the figure denoting the proximal ends of the holes and the lower part of the figure denoting the distal ends of the holes;100625635642

[0190] Figure 43 is a schematic longitudinal cross-sectional view of a mine environment illustrating holes of two spaced apart rings angled towards one another in accordance with another step of the method of creating a blasting void;

[0191] Figure 44 is a schematic transverse cross-sectional view of the mine environment of Figure 43 illustrating holes of the two spaced apart rings;

[0192] Figure 45 is a photograph of another suitable paste drill bit that can be utilised to create a blasting void in backfill material;

[0193] Figure 46 is a schematic top view of a suitable pattern of void holes in backfill material, in this case a single row of holes illustrating the width to depth ratio of the blasting void;

[0194] Figure 47 schematic top view of a suitable pattern of void holes in backfill material, in this case two rows of holes illustrating the width to depth ratio of the blasting void; and

[0195] Figure 48 is a schematic transverse cross-sectional view of a mine environment illustrating holes from a single ring, in particularly illustrating the varying width to depth ratio along the height of the blasting void.Detailed description of the embodiments

[0196] As a precursor to understanding the disclosure, reference is made to Figures 1-5 to illustrate the technique of “open stoping” or “long hole stoping”, which is used for accessing and retrieving a mineral or metal ore O from an ore body B in underground mining. As shown in Figures 1 and 2, this involves a process of excavating, in the depicted embodiment drilling, blast holes H using a long-hole drilling rig D, with the blast holes H extending between two tunnels or drives Tu, TL that form working chambers for miners or operators at two levels within or adjacent to an ore body B. The ore body B is progressively mined in sections or blocks between the upper tunnel Tu and the lower tunnel TL and these sections or blocks of the ore body B are called “stopes” S.

[0197] Before drilling blast holes H, a ‘rise’ or ‘winze’ can be formed by drilling a pattern of holes (numbered 1-17 in Figure 3a) between the upper and lower tunnels Tu, TL in a next stope S to be mined, as shown in Figure 2. Some of those holes are then100625635643fired in a manner like a ‘burn cut’ used in drill and blast tunnelling. Once material from the fired holes has been removed, the void remaining forms a ‘rise’ or ‘winze’ (not shown) that provides space into which the rock can expand when charges set in blast holes H are detonated or “fired”. That is, for the charges in the blast holes H to break up the ore body B successfully, there must be sufficient space into which the rock can expand on firing. If a reamed hole W, such as a “raise bore”, is used, the diameter of the hole Wwill typically be significantly larger than the blast holes H, as shown in Figure 3b. After forming the long hole rise or the reamed hole W, the blast holes H (numbered 1-12 in Figure 3b) are drilled to extend generally parallel to, and at a range of distances from, the reamed hole W. The charges (not shown) are then set in the blast holes H to be fired sequentially. The process of establishing the rise or reamed hole W is difficult, costly, and high risk due to the multitude of issues that can arise during drilling and blast activities.

[0198] It will be understood that a rise or reamed hole as mentioned above can also be referred to as a blasting void.

[0199] As seen in Figures 4 and 5, the ore body B in this example has a vertical height h of about 20 metres between the upper tunnel Tu and the lower tunnel TL. Because the ore body B in this particular case lies in the surrounding rock strata at an angle of about 45 degrees, however, the length I of the ore body B at a wall or face F of the next unmined stope S is about 28 metres. The width w of the stope S in this case is about 5 metres and largely corresponds to the width of the ore body B to minimise the extraction of rock not containing ore. The previously mined, and now open stope So seen in Figure 4 forms a chamber with a depth d of about 20 metres, which extends to a wall formed by backfill material BM filled into the preceding or previously mined stope.

[0200] The above description is just one example of typical “open stoping” or “long hole stoping” processes, and the dimensions of the ore body are just exemplary. In practice, the size, shape and orientation of various ore bodies vary greatly, thereby necessitating variations on the precise implementation of the known techniques used.

[0201] The process of establishing the blasting void is often a very difficult, high cost, and high risk component of mining a stope. In view of this, the inventors have developed improved methodologies for creating the blasting void that can speed up100625635644production cycle times for a mine. The core premise underpinning the methodologies is to move away from the industry accepted technique of creating the blasting void in the hard rock of the unexcavated stope / ore body and to instead create the blasting void in the backfill. Establishing blasting voids in the hard rock requires specific hard rock-type drills, bits, cutters and methodology (some of which require explosives). These added, costly layers can be circumvented by employing methodologies disclosed herein, thereby resulting in great benefits to a mine in terms of scheduling, production equipment availability, cost, and production efficiency.

[0202] Reference is made to Figures 6-9 that illustrate one embodiment of a method for creating a blasting void during underground mining. In this embodiment, the blasting void is created directly in the backfill material after a conventional backfill operation of an open stoping or long hole stoping process.

[0203] As shown in Figure 6, which serves as a starting point for illustrating the method, upper ore drive Tu and a lower ore drive TL have already been developed through respective mining levels along a strike of the ore body B, and an initial section of stope has been blasted and is ready for removal via lower ore drive TL in the usual manner. In this example, the formation of the initial blasting void that enables blasting of the first stope (labelled Stope 1 in Figure 6) can be formed using known blasting void creation techniques previously described, in which the blasting void is formed in the hard rock material of the unexcavated stope.

[0204] As used herein, reference to a longitudinal direction of the ore body / stope is a reference to the direction in which the ore drives extend (i.e. left to right in Figure 6). As used herein, reference to a transverse direction of the ore body / stope is a reference to the width direction of the ore body / stope (i.e. into / out of the page in Figure 6). As used herein, reference to a vertical direction of the ore body / stope is a reference to the height direction of the ore body / stope.

[0205] Once the broken ore of Stope 1 has been removed, the open stope So that has been created is backfilled with a suitable backfill material BM as shown in Figure 7. For the present example, a paste backfill has been used. However, a person skilled in the art will appreciate that there are various suitable backfill materials that can be used. The method of this embodiment is particularly well suited for applications where a flowable100625635645backfill material is used. After the backfill material BM has cured, the method moves to mining the next section of stope (Stope 2 in Figure 7).

[0206] Up until now, what has been carried out is simply the conventional open stoping or long hole stoping process. Typically, the procedure would simply repeat with the next blasting void created in the hard rock material of Stope 2, adjacent to an interface between the unexcavated stope and the backfill material. However, the methodology of this disclosure now differs.

[0207] As shown in Figure 8, a blasting void BV is formed directly in the backfill material, near the interface between the unexcavated stope and the backfill material BM. This represents a significant departure from known techniques. In the present embodiment, a plurality of holes 30 (Figure 10) are drilled in close proximity to one another such that the plurality of holes 30 together define the blasting void BV. By ‘close proximity’, it is meant the plurality of holes 30 are close enough to one another such that two or more of the plurality of holes may intersect one another along their respective lengths and / or that any unexcavated material disposed between adjacent, nonintersecting holes is of little structural integrity so as to effectively create a continuous blasting void due to unexcavated material between adjacent holes providing minimal resistance to blasting operations. The plurality of holes 30 in this embodiment are drilled from the upper drive Tu down towards the lower drive TL. In an embodiment such as this one where an upper and lower drive are provided, the plurality of holes 30 will generally extend all the way from upper drive Tu and break through into the lower drive TL.However, this need not be the case, and in embodiments where there is only a single access drive (rather than upper and lower drives), the plurality of holes will extend a desired distance generally corresponding to the expected height of the stope (this expected height may be determined via suitable surveying techniques).

[0208] Further, the plurality of holes 30 are disposed near an interface between the backfill material BM and an unexcavated stope (i.e. the next stope to be mined, Stope 2 in Figure 8). For certain mines, the optimal placement of the plurality of holes 30 may be at a location that is as close to the interface between the backfill material BM and the unexcavated stope as possible / practical (whilst substantially extending into the backfill material). A person skilled in the art will appreciate that the precise positioning of the100625635646holes can be different from mine to mine, as well as different for different ore bodies. Other factors that may influence the precise positioning of the holes include the condition of the nearby material, size of the plurality of holes forming the blasting void, as well as the size, shape and arrangement of the blast holes in the unexcavated stope. To this end, the plurality of holes can be arranged such that they are within a suitable distance to the blast holes (that are to be formed in the hard rock material of the next stope to be mined) to ensure the blast can propagate towards the blasting void through burden disposed between the blast holes and the plurality of holes defining the blasting void. The ideal distance between the plurality of holes in the backfill material defining the blasting void and the blast holes formed in the hard rock material will vary case to case (e.g. a suitable distance could be between 0.5 m to 5 m, but it could also be more or less).

[0209] An example of a suitable arrangement or pattern of the plurality of holes 30 is shown in Figure 10. In this figure, the plurality of holes 30 are disposed within a generally elongate ‘blasting void hole region’ 40 disposed at the backfill material BM, near an interface 35 between the backfill material BM and the unexcavated stope S. The generally elongate blasting void hole region 40 extends in this case in the transverse direction, i.e. along the width direction of the stope. The plurality of holes 30 are in close proximity to one another such that the unexcavated material disposed between the holes is of little structural integrity so as to effectively create a continuous blasting void due to unexcavated material between adjacent holes providing minimal resistance to blasting operations. It will be appreciated that what is depicted in Figure 10 is only one example of a suitable arrangement or pattern of the plurality of holes 30.

[0210] Another example is shown in Figure 41 , which illustrates a staggered pattern -in this case an approximately 60° staggered pattern including a first substantially linear row of holes and a second substantially linear row of holes, the rows being spaced apart from each other (in this case, spaced along the longitudinal direction with the rows generally extending in the transverse direction). It will appreciated by a person skilled in the art the that the arrangement of the plurality of holes will generally depend on mine site-specific parameters.100625635647

[0211] Another example is shown in Figure 42, which is similar to the example of Figure 41 in that it illustrates an approximately 60° staggered pattern including a first substantially linear row of holes H1 and a second substantially linear row of holes H2 spaced apart therefrom each other. In this example, the upper part of Figure 42 illustrates the proximal ends of the holes, i.e. the end of the holes closest to the ore drive, whereas the lower part of Figure 42 illustrates the distal ends of the holes. It will be appreciated that the second substantially linear row of holes H2 are angled with respect to the first substantially linear row of holes H1 such that the distal ends of the holes of the second substantially linear row of holes H2 are positioned closer to the distal ends of the holes of the first substantially linear row of holes H1.

[0212] It will be understood that having the distal ends of the holes converge (or otherwise be positioned closer together) can be beneficial for establishing a continuous or substantially continuous blasting void, particularly at or near the interface between the backfill material and the unexcavated stope, for example by reducing unexcavated material disposed between adjacent holes and assisting propagation of blasting between the holes. It will also be understood that the degree and direction of angling of the holes (e.g. one or both of inclination and azimuthal orientation) can be selected and varied as desired in accordance with blast design requirements and mine site-specific parameters. Further, whilst Figures 41 and 42 depict the first and second substantially linear rows of holes as generally straight when viewed in plan, it will be appreciated that in other embodiments the holes may be arranged along an arc or portion of a ring (e.g. as one or more rings), including where the first and second rows are provided as spaced-apart ring formations.

[0213] Figures 43 and 44 further illustrate an example arrangement of holes formed from an ore drive, wherein the holes are angled such that the respective distal ends converge toward one another. In particular, Figure 43 illustrates a longitudinal section view of an ore drive and illustrates a hole from each of the first and second rows (or rings) of holes, showing how each hole may be angled such that the distal ends of the holes converge toward each other. Figure 44 illustrates a transverse section view through the ore drive of Figure 43, showing the distal ends of the holes of the first ring and the distal ends of the holes of the second ring in close proximity so as to create a100625635648continuous or substantially continuous blasting void, with a portion of the distal ends shown in circle A in Figure 44.

[0214] Conventional underground drill and blast practices for blast holes is to design the holes to be a certain distance apart with the material (hard rock) between the holes being fired out during blasting activities, for example a standard long hole rise. This distance will vary depending on the blast hole diameter and type or density of explosives used. The material (hard rock) between the blast holes is of such structural integrity that it must be ‘blasted out’ in order to be removed. In contrast to conventional underground hard rock drill and blast practices, the spacing of the holes that form the blasting void(s) in the backfill can be designed so as they are as close together as practical (or in some cases to intersect) that is, the backfill material between them is of little structural integrity and does not need to be removed with the aid of explosives or ‘blasted out’. This is a departure from known drill and blast methodology / practices, which requires explosives to remove the material between the holes.

[0215] It will be understood that, in practice, the geometry and available dimensions of an ore drive (and / or other mine site-specific constraints), together with factors such as drill deviation, can mean that a desired proximal end pattern does not necessarily result in a desired spacing between the distal ends of adjacent holes. Accordingly, in some embodiments the predetermined pattern of the holes is selected to compensate for such factors so that the distal ends of holes of adjacent rows and / or rings are in sufficiently close proximity (and / or intersect) to ensure that a continuous or substantially continuous blasting void is formed at or near the interface between the backfill material and the unexcavated stope, thereby reducing a risk of an ineffective blast (e.g. bridging) due to excessive unexcavated material remaining between adjacent holes. In some implementations, one or more holes may additionally, or alternatively, be reamed (or otherwise formed) to have an increased diameter in order to further reduce unexcavated material between holes and assist in establishing the continuous or substantially continuous blasting void, wherein the selection of hole diameter, distal end spacing and / or reaming is in accordance with blast design requirements.

[0216] It will also be appreciated that, in some mine environments, ground support may be installed at or near a proximal end location from which one or more of the holes 30100625635649are to be drilled in the backfill material BM. By way of example, such ground support may include shotcrete or fibrecrete, rock bolts (e.g. split sets or other bolt types), mesh (e.g. steel mesh, polymer mesh or other mesh types), or combinations thereof.Accordingly, in some embodiments the predetermined pattern (and / or the location of one or more proximal ends) is selected having regard to the presence and / or planned installation of such ground support, for example so as to avoid undesirable intersection of the holes 30 with one or more ground support elements. In some embodiments, one or more ground support elements may be removed and / or may be omitted (or not installed) at one or more proximal end locations to facilitate drilling of the holes 30, and / or survey pick-ups of ground support elements may be used to assist in designing or selecting the predetermined pattern and the location of the holes 30 in the backfill material BM.

[0217] It will be appreciated that Figure 8 is schematic, showing a straight edge between the unmined section of stope (i.e. the next stope to be mined) and the region that has been backfilled. In practice, the uneven nature of the rock face may mean that excavating the plurality of holes in the backfill will also result in partial excavation of the hard rock material associated with the unexcavated stope at an interface thereof.

[0218] An advantage in forming the plurality of holes 30 in the backfill material BM is that the backfill material BM has significantly less compressive strength than the hard rock material of the unexcavated stope S. In the case of a paste backfill, its compressive strength after curing is typically about 0.5-10 MPa, whereas the compressive strength of the hard rock material can be about 50-250 MPa. Given that the present embodiment need only involve drilling into the paste backfill to form the blasting void BV, standard production drill rigs can be used to create the plurality of holes 30, rather than the more specialised hard rock-specific equipment and methodology. A further advantage is the ability to use significantly larger size drill bits, thereby forming significantly larger holes than would typically be created in some other blasting void formation methodologies. For example, drill bits having a diameter up to 1500 mm (or more) can be used, as compared to conventional methodologies where drill bits no greater than 204 mm would typically be used. However, it may be practical for certain embodiments of hole arrangements to utilise drill bits having diameters that are less than or equal to 204 mm.100625635650

[0219] An example of suitable drill bits 50a, 50b that can be employed when the backfill material is a paste-type backfill are shown in Figures 17a and 17b. The drill bits 50a, 50b of Figure 17a-b each include three circumferentially equispaced wing portions 52a, 52b (only two are apparent from the figures). The drill bit 50a of Figure 17a has a diameter of 500 mm, whereas the drill bit 50b of Figure 17b has a diameter of 350 mm. Notably, unlike typical hard rock bits, such as button bits, that rely on percussive drilling to break rock, the drill bits 50a, 50b of Figure 17a-b include cutting teeth that are configured to cut through the backfill material by predominantly rotary drilling (i.e. with minimal or low percussion). This represents a significant departure from known underground hard rock drill bits used to form blasting voids in conventional mining methodologies, for example, drill and blast mining. This enables soft rock drilling methodology (e.g. rotary drilling with minimal percussion and aggressive-type cutting teeth) to be employed, rather than hard rock drilling methodology (e.g. percussive drilling with button or cross bits).

[0220] Some of the details of drill bits 50a, 50b of Figure 17a-b are shown in the below table.

[0221] Another example of a suitable drill bit 50c is shown in Figure 45. Drill bit 50c shares various features with drill bits 50a, 50b, and notably more clearly illustrates the cutting teeth. Drill bit 50c further includes hardfacing portions, i.e. regions having a wear-resistant material applied thereto. For example, the hardfacing portions may be formed by applying (e.g. welding, brazing or otherwise depositing) a relatively hard, abrasion-resistant overlay to selected surfaces of the drill bit that are prone to wear in100625635651use. Advantageously, hardfacing can assist to reduce wear of the drill bit body and / or cutting structures and can thereby extend service life of the drill bit when drilling through abrasive backfill material.

[0222] It will be appreciated that, for drilling the plurality of holes 30 in backfill material BM, selection of a suitable drill bit (and associated drilling parameters) can be important to achieve an efficient drilling operation and an acceptable service life of the drill bit. The drill bit employed can be configured for two-pass drilling applications (e.g. pilot hole followed by separate reaming) or single-pass drilling. For example, in some embodiments the drilling may be performed in a single pass using a stepped drill bit configuration including a pilot bit and a reamer bit. In other embodiments, the drilling may be performed in multiple passes, for example by drilling a pilot hole followed by reaming using a drill bit having a lead section configured to track or follow the pre-drilled pilot hole.

[0223] Whilst the drill bits 50a-c include a single coupling (e.g. a female coupling) at one end of the drill bit, it is envisaged that a drill bit of similar form may be provided having include a coupling at each end such that, when cutters at one end are worn or damaged, the drill bit can be reversed and used from the other end to increase service life. In some embodiments, drilling can be undertaken using water, air, or an air mist as a drilling fluid / medium, and a person skilled in the art will appreciate that backfill material properties can influence selection of suitable drilling settings. A further advantage of using a drill bit with cutters (including where hardfacing is applied to high-wear regions) is that the backfill material is less likely to block the drill bit during drilling, which can be advantageous relative to certain drill bits commonly used for production drilling in hard rock.

[0224] As noted above, backfill material BM can be abrasive and can therefore contribute to wear of components of the drill bits used to form the plurality of holes 30. Accordingly, in some embodiments the drill bit may be configured and / or manufactured to improve wear resistance, for example by selecting a suitable extent, pattern and / or coverage of the hardfacing on high-wear surfaces of the drill bit. In some embodiments, one or more metallurgical treatment methods may be applied to the drill bit and / or to one or more components thereof (e.g. heat treating). In some embodiments, the100625635652geometry of one or more cutting teeth may be selected to suit drilling through the backfill material BM, for example by use of pick-type teeth disposed at an angle (e.g. about 45 degrees) relative to a surface of the drill bit. In some embodiments, the drill bit and / or its components may be formed of, or include, one or more of: steel (including suitable steel grades such as 4140), engineering polymers (e.g. nylon), composite materials (e.g. steel / polymer composites), and tungsten carbide (e.g. for cutter teeth). It will be understood that selection of suitable materials and configurations may take into account one or more material properties, such as machinability, wear resistance, toughness, hardness and durability. A person skilled in the art will appreciate that selection of a suitable drill bit configuration (including materials and material properties) for a given application can be made having regard to factors such as backfill characteristics, desired hole dimensions, drilling method (single-pass or multi-pass), and desired wear life.

[0225] It will be understood that when using standard underground drilling machines (e.g. production drill rigs) to drill the holes 30, the drill rig settings will need to be adjusted to enable for drilling of the relatively larger diameter holes. A person skilled in the art, such as a qualified drill rig fitter, may be required to adjust the drill rig settings (e.g. percussion, feed, rotation) to enable safe drilling of the larger diameter holes.

[0226] Whilst not shown directly in Figure 8 (although more apparent from Figure 10), an important aspect of the present embodiment is the creation of a blasting void BV having a width dimension greater than a depth dimension in cross-section. In other words, when viewed in plan, the blasting void BV is wider than it is deep. For clarity, with respect to Figure 8, the width of the blasting void BV is to be understood as extending in the transverse direction (into the page when looking at Figure 8), whilst the depth of the blasting void BV is to be understood as extending in the longitudinal direction (to the left and into the backfill material when looking at Figure 8). The precise width to depth ratio can vary depending on the particular application, but this ratio could be anywhere greater than about 1.1:1, such as from about 1.1:1 to about 75: 1. For example, the blasting void BV formed by the collective of holes 30 may have a width to depth ratio of 1.5:1 (350 mm depth, 525 mm wide), a width to depth ratio of 2:1 (350 mm depth, 700 mm wide), a width to depth ratio of 5:1 (500 mm deep, 2500 mm wide), a width to depth ratio of 10:1 (500 mm deep, 5,000 mm wide), up to 75:1 (200 mm100625635653depth, 15000 mm wide) etc. Tables further below provide further examples of suitable width to depth ratios. In the most ideal situation (at least for certain applications), the width of the blasting void would effectively correspond to the width of the stope. An advantage of creating a blasting void of greater width than depth is that the blasting void provides a wider target for blast holes to blast towards (and therefore a wider area to through rock towards). It will be appreciated that multiple blasting voids, spaced along the width of the stope, could be formed by this method. In other words, holes can be formed in the backfill material that are spaced apart a sufficient distance that unexcavated material disposed between non-intersecting holes is of sufficient structural integrity to resist blasting operations, meaning that holes spaced in such a way each represent a blasting void. For ease of illustration, the examples depicted herein show formation of a single blasting void.

[0227] As shown in Figure 9, the next stage of the method includes drilling the blast holes H into the hard rock of the next stope to be mined (Stope 2 in this example). The blast holes H are formed in several ‘production rings’ - a plurality of longitudinally spaced arcs, wherein each arc includes a series of blast holes spaced generally circumferentially about the respective arc and extending in a generally radial or vertical direction with respect to a given drive (only a single blast hole of one production ring is shown for clarity in Figure 9). In the present embodiment, the production ring is formed at the upper drive Tu, with the blast holes extending generally downward and radially into Stope 2. Referring again to Figure 10, part of a first production ring of blast holes H is shown near interface 35 and therefore near holes 30 that form the blasting void. It will also be apparent from Figure 10 that part of a second production ring of blast holes H is shown, in this case longitudinally spaced away from the first production ring of blast holes H.

[0228] Once the blast holes H have been suitably loaded with explosives, the blast holes H are fired in a predetermined sequence (typically, firing sequentially the holes of a first production ring, followed by firing sequentially the holes of a second production ring, and so on) causing the nearby hard rock to be thrown towards the blasting void BV. It will be appreciated that the predetermined firing sequence may vary depending on mine site-specific parameters, such as stope geometry, hole diameter and other drilling and blasting considerations. In one example, firing of a production ring may100625635654include firing one or more central holes first so as to create a trench-like void in the hard rock, with remaining holes (e.g. hanging wall and foot wall holes) then fired in sequence to blast toward the blasting void BV in the backfill material and / or toward the trench-like void in the hard rock.

[0229] A key aspect of this embodiment relates to the positioning and overall shape of the blasting void BV. It will be understood that the blasting void BV is configured to facilitate expansion of blasted material from the unexcavated stope towards the blasting void in a generally ‘forward’ direction as shown by the arrow in Figure 9. The generally forward direction is to be understood as the direction from the unexcavated stope to the backfill material BM. In this regard, it will be understood that the holes 30 defining the blasting void BV are positioned forward of the blast holes H (i.e. formed in the backfill material BM on an opposite side of the interface to the hard rock in which the blast holes H are formed). This is advantageous relative to known blasting void formation methodologies that typically start by forming a central bore, followed by a series of blast holes around the central bore, with these holes fired in a specific sequence to ‘open up’ the blasting void by throwing the blasted material inwardly towards the central bore (see Figure 3b for example). In contrast, forming the blasting void BV in the backfill material BM, with blast holes H formed in the hard rock material (near the backfi ll / hard rock interface) the blasted material is blasted in a generally single, forward direction towards the blasting void BV formed in the backfill. Put differently, the direction of a substantial portion of the blast energy is in this generally forward direction. It will be appreciated that this generally forward direction of expansion of the blasted material is not only enabled by the position of the blasting void, but also by the relatively greater width of the blasting void.

[0230] The broken ore can now be retrieved, and the method can be repeated until the whole ore body has been mined.

[0231] Reference is made to Figure 11 , which is an image of a successful trial of the method. In this particular trial, two sets of holes 30 were placed in the backfill material BM near the interface between the backfill material and next stope to be mined, with the two sets of holes together forming a continuous blasting void BV. It will be appreciated that the two sets of holes in this example are spaced apart longitudinally to one another.100625635655Three production rings, i.e. three sets of blast holes Hi , H2, H3, were also employed and fired in sequence. When the first ring Hi (the ring closest to the interface between the backfill material and the unexcavated stope) blasted, the stope blasted to the right most void holes of the continuous blasting void, thereby creating a larger void for the subsequent rings to blast towards. The continuous outline 35 that is superimposed on Figure 11 demonstrates the outcome of the blasts.

[0232] As will be appreciated from the above, an improved method of forming a blasting void when mining underground is provided. Unlike known prior art methods that involve formation of the blasting void in the hard rock material of an unexcavated stope (having, for example, a compressive strength in the order of about 50-250 MPa), the formation of a blasting void in the backfill material (having a compressive strength in the order of, for example, about 0.5-10 MPa) provides substantial advantages. One advantage is that the blasting void can be created using standard mine production drilling rigs, rather than the more specialised hard rock-type equipment and methodology (e.g. hard-rock drills, bits, cutters, specific sequences, interactions and mine operations typically required to establish the blasting void). For example, the same mine production drilling rig formed holes 30 and blast holes H of Figures 10 and 11. This enables the blasting void to be established in significantly less time than would typically be the case using conventional blasting void formation methodology, such as drill and blast (i.e. bum cut), drilled / bored rise (i.e. raise bore), and box hole processes. This has significant benefits to a particular mine in terms of scheduling, production equipment availability and cost of additional equipment and contractors.

[0233] Another advantage is the reduction in mine cycle time given the reduced time in forming the blasting void and therefore the reduction in time to carry out a typical ore recovery process. Creating the blasting void is known as being a costly and time intensive part of the ore recovery process and therefore simplifying this stage of the process is greatly beneficial to the mine.

[0234] A further advantage is that the blasting void can be created without using explosives, thereby saving on the cost and time associated with blasting at this stage of the process.100625635656

[0235] Reference is made to Figures 12-16 that illustrate another embodiment of a method for creating a blasting void during underground mining. In this method, the blasting void is created in the backfill material before a conventional backfill operation of an open stoping or long hole stoping process.

[0236] As shown in Figure 12, which serves as a starting point for illustrating the method, upper ore drive Tu and a lower ore drive TL have already been developed through respective mining levels along a strike of the ore body B, and an initial section of stope has been blasted and is ready for removal via lower ore drive TL in the usual manner. In this example, the formation of the initial blasting void that enables blasting of the first stope (labelled Stope 1 in Figure 12) can be formed using known blasting void creation techniques previously described, in which the blasting void is formed in the hard rock material of the unexcavated stope.

[0237] As shown in Figure 13, once the broken ore of Stope 1 has been removed, an excavatable plug 60 is deployed into the open stope So, with the plug 60 disposed adjacent a wall or face F of a next stope to be mined (Stope 2 in Figure 13) and oriented to generally abut said wall or face of Stope 2. It will be appreciated that the plug need not be positioned in this manner, with it instead being spaced away but still near the wall or face F of the next stope to be mined.

[0238] Plug 60 includes an excavatable material 62 that is encased by an elongate, tubular casing 64. It will be appreciated that the casing need not be tubular, and can assume another suitable form (e.g. a hollow section of different shape / configuration). As will be described in further detail below, excavatable material 62 is to be excavated or otherwise removed from the casing 64 at a suitable point in the method in order to form a blasting void. The blasting void will therefore defined by an interior volume of the casing 64 after removal of the excavatable material 62.

[0239] It will be appreciated that Figure 13 is schematic, showing a straight edge / straight face F between the unmined section of stope (i.e. the next stope to be mined) and plug 60. In practice, the uneven nature of the rock face may mean that plug 60 will need to be suitably oriented, such as being angled, in order to attain the desired position with respect to said wall or face F of Stope 2.100625635657

[0240] In certain embodiments, the casing 64 can be deployed in position first, followed by a subsequent step of filling the casing 64 with the excavatable material 62. In alternative embodiments, plug 60 is a pre-cast element - either being formed of both a casing 64 and a excavatable material 62, or simply just the excavatable material in a cast form. In an embodiment having the casing 64, it will be understood that the casing 64 is configured to withstand internal pressure imparted by the excavatable material 62 onto an interior of the casing 64, such that the casing 64 does not rupture, crumple or otherwise be sufficiently damaged to impact its functionality, particularly when filling said casing 64 with the excavatable material 62. Casing 64 is also configured to prevent leakage of the excavatable material into the surrounding mine. In this regard, the formation of the casing may be such that it is a sufficiently closed structure, although this need not be the case depending on the excavatable material employed. A lining or other barrier may also be provided inside the casing to provide the necessary leak protection.

[0241] Plug 60 is preferably secured to the wall or face F of Stope 2 to prevent or limit its movement at varying stages of its operational life. Plug 60 may be secured at the top drive, bottom drive or a combination of both. Suitable means for securing plug 60 may include fastening to the respective drive with chains, securing to the floor with rock bolts or securing to a part of the delivery system that installs the plug. However, plug 60 may otherwise be simply arranged so as to generally abut against or be disposed near the wall or face F of Stope 2 without additional securement (in such a case, a notch could be formed in the wall or face F of Stope 2 to assist in partially receiving plug 60).

[0242] Once plug 60 has been suitably deployed, the open stope So that has previously been created is backfilled with a suitable backfill material BM as shown in Figure 14. For the present example, a cemented rockfill has been used as the backfill material. However, a person skilled in the art will appreciate that there are various suitable backfill materials that can be used, both flowable and non-flowable backfill materials. The method of this embodiment is particularly well suited for applications where a cemented rockfill or similar is used. It will be understood that the plug 60 is configured to withstand external pressure imparted by the backfill material BM onto an exterior of the plug 60, such that the plug 60 does not rupture, crumple or otherwise be sufficiently damaged to impact its functionality during the backfill operation.100625635658

[0243] After the backfill material has cured (if required), the method moves to creating the blasting void. As shown in Figure 15, the excavatable material 62 (or a portion thereof, preferably a substantial portion thereof) is excavated with casing 64 remaining. Casing 64 is configured to enable a blast to propagate through to the blasting void in its interior (i.e. provide relatively minimal resistance to the oncoming blast energy. In this embodiment, excavatable material 62 is drilled out, thereby creating a blasting void BV extending between the upper and lower ore drives TU,TL proximate to an interface between the backfill material BM and the unexcavated stope. A drill bit such as the one earlier described could be used, or in other implementations another suitable drill bit may be used. The considerations around what drill bit is suitable will depend on the excavatable material. It will be understood that in this example, only the excavatable material 62 has been excavated. However, this need not be the case. In another example, the excavatable material 62 and the casing 64 is excavated (or otherwise removed).

[0244] Excavatable material 62 is a material of lower compressive strength than the unexcavated stope. The excavatable material may be in the form of one or more of: mine tailings (wet or dry), sand, gravel, paste fill, or other excavatable material. Thus, similar to the earlier embodiment, this embodiment relies on creating the blasting void in significantly softer material than the hard rock material of the unexcavated stope.

[0245] Casing 64 may be formed of any suitable material capable of withstanding the loads experienced by plug 60 in use. A robust material and preferably a durable, high-density material, such as steel or reinforced concrete, which will be capable of withstanding high loads in use, may be used. In this regard, for example, when a backfill material such as a waste rock or similar is used, the casing will typically be subject to impact loading and abrasion during the backfilling process and it should therefore be sufficiently strong and durable to readily withstand the loading conditions. It will be appreciated, however, that the casing may also be comprised of a robust and durable, light-weight material, such as an engineering plastic, especially when the loading expected during backfilling may be lower, as is the case when backfilling with a flowable backfill material such as mine tailings or paste fill pumped into the stope. Examples of engineering plastics include polyamide (PA, Nylon), polyethylene (PE, HDPE), polyvinylchloride (PVC), polycarbonate (PC), and polyurethane (Pll). It will also be100625635659appreciated that composite materials, such as fibre-reinforced polymers, may be suitable in certain applications.

[0246] In general, in order to determine a suitable material and design in which to make the plug / casing, it is important to understand the loads it will be exposed to. When placing a plug into a void (such as a stope prior to backfilling), it can be exposed to a variety of different loading combinations (e.g. tensile, shear and compressive forces, being moments, etc). Computer modelling software is an appropriate tool to use to enable selection of suitable materials and variations in the design of the plug, including changes in shape / geometry. A person skilled in the art - such as materials, geotechnical, mining, structural, civil and hydraulic engineers / specialists - will appreciate that Finite Element Analysis (FEA) is a commonly used computational method used to predict how a product or structure will react to real-world forces, vibrations, heat, and other physical effects by breaking down the object into smaller elements and using mathematical equations to simulate its behaviour. FEA is an example of an appropriate tool which can be used to facilitate the material selection and design of the plug at all stages of its operational life, such as: casing being placed in the stope prior to filling it with excavatable material to form the plug; hydraulic forces the casing is exposed to as the casing is being filled to from the plug; design and reinforcement support requirements for a pre-cast plug installation; loads exerted on the plug during backfilling operations, etc. FEA is also commonly used to model the geotechnical properties and rock mass conditions at mine sites which may also provide useful information for the implementation of the overall methodology, for example geotechnical stability of an open stope. FEA is a cost-effective process which can be undertaken relatively quickly depending on the information required / detail of the design. Thus, it is well within the skillset of a person skilled in the art to tailor the plug / casing design to a given application without prolonged research or tests that go beyond routine trial and error.

[0247] In addition to, or as an alternative to, FEA, a person skilled in the art will be able to generally estimate the loading that the casing or plug will need to withstand in order to perform the desired function within the described methodology. Design of a suitable casing or plug can be aided by one or more of the following mathematical equations (the values provided for exemplary purposes only):100625635660The potential energy which the casing / plug may be exposed to can be estimated by: Potential Energy = mass*gravity*heighte.g. 1,000kg of backfill material falling 15m onto the casing / plugPE = 1000kg*9.81m / s2*15mPE = 147.15 kJThe forces that the casing / plug may be exposed to can be estimated by: Force = (mass*gravity*height) I stopping distance.e.g. 1000kg of backfill falling 15m onto the casing / plug and coming to rest over 100mmF = (1000kg*9.81m / s2*15m) / 0.1mF =1,471.5 kNThe hydraulic pressure that the casing / plug may be exposed to can be estimated by: Pressure = density* gravity*heighte.g. the pressure on the casing / plug when exposed to 10m of flowable backfill with a density of 1 ,500km / m3Pressure = 1 ,500 kg / m3 * 9.81 m / s2*10mPressure = 0.147 MPa

[0248] It will also be appreciated that the casing / plug may be exposed to point loading during the backfill process. An example of this is a large rock striking the casing / plug. Design considerations to account for this include the shape of the casing / plug, the provision of one or more deflector elements to redirect backfill from directly striking the casing / plug, a protective layer with reinforcement or shock absorption properties such as a suitable metal (e.g. steel), plastic or rubber material, etc. Consideration of a given materials properties is essential to ensure a suitably designed plug / casing is produced for a given application. This is why software modelling, such as FEA, which can take into account material properties during an analysis, is particularly useful as it enables100625635661ready selection and changing of material within the software, thereby enabling a quick and cost effective method to model different designs and materials for a particular application.

[0249] In certain applications, the casing is in the form of a unitary element. In other applications, the casing may be formed of a plurality of casing elements.

[0250] Given that the present embodiment need only involve drilling into the excavatable material of the plug to form the blasting void (although as described above one could also drill out the casing as well), standard production drill rigs can be used to create the hole, rather than the more specialised hard rock-specific equipment and methodology. A further advantage is the ability to use significantly larger size drill bits, thereby forming significantly larger holes than would typically be created in some other blasting void formation methodologies. For example, drill bits having a diameter up to 1500 mm (or more) can be used, as compared to conventional methodologies where drill bits no greater than 204 mm would typically be used. This means that the diameter of the plug can be accordingly large.

[0251] As shown in Figure 16, the next stage of the method includes drilling the blast holes H into the hard rock of the next stope to be mined (Stope 2 in this example). The blast holes H are formed in several ‘production rings’ as previously described (only a single blast hole of one production ring is shown for clarity in Figure 16). In the present embodiment, the production ring is formed at the upper drive Tu, with the blast holes extending generally downward and radially into Stope 2.

[0252] Once the blast holes H have been suitably loaded with explosives, the blast holes H are fired in a predetermined sequence (typically, firing sequentially the holes of a first production ring, followed by firing sequentially the holes of a second production ring, and so on) causing the nearby hard rock to be thrown towards the blasting void BV. A key aspect of this embodiment relates to the positioning and overall shape of the blasting void BV. Whilst not shown directly in Figure 16, an important aspect of the present embodiment is the creation of a blasting void BV having a width dimension greater than a depth dimension in cross-section (by using a suitably shaped plug / casing, using multiple plugs / casings disposed near each other, excavating a suitably shaped hole of the excavatable material, etc). In other words, when viewed in100625635662plan, the blasting void BV is wider than it is deep. For clarity, with respect to Figure 16, the width of the blasting void BV is to be understood as extending in the transverse direction (into the page when looking at Figure 16), whilst the depth of the blasting void BV is to be understood as extending in the longitudinal direction (to the left and into the backfill material when looking at Figure 16). The precise width to depth ratio can vary depending on the particular application, but this ratio could be anywhere greater than about 1.1:1, such as from about 1.1:1 to about 75: 1.

[0253] Calculations of example width to depth ratios are presented in the below tables to provide the person skilled in the art with reference material to assist in the designing of a blasting void in backfill. The first table shows example width to depth ratios for different size drill bits for a single row of void holes drilled in mine backfill. The second table shows example width to depth ratios for different depth blasting voids established by drilling multiple rows of holes in backfill.100625635663Above table showing width to depth ratios forblasting voids formed from a single row of holes with different diameter drill bitsAbove table showing width to depth ratios for blasting voids formed from multiple row of holes

[0254] An advantage of creating a blasting void of greater width than depth is that the blasting void provides a wider target for blast holes to blast towards (and therefore a wider area to through rock towards). This can have the advantage over conventional slot methods (such as raise bores and long holes rises) as it allows for the blasting void to correspond to the shape of the stope which is to be mined. This is illustrated in Figures 46-48, where it is shown that the width of the blasting void formed in accordance with this disclosure is wider than it is deep, with Figure 48 in particular showing that the width to depth ratio can vary along the height of the blasting void as shown, where the width of the blasting void is wider at point A than it is at point B.100625635664

[0255] It will be appreciated that multiple blasting voids, spaced along the width of the stope, could be formed by this method (using multiple plugs / casings). In other words, plugs / casings can be set in the backfill material, spaced apart a sufficient distance that unexcavated material disposed between the plugs / casings is of sufficient structural integrity to resist blasting operations.

[0256] It will be understood that the blasting void is configured to facilitate expansion of blasted material from the unexcavated stope towards the blasting void BV in a generally ‘forward’ direction as shown by the arrow in Figure 16 and previously described. In an application where the casing 64 of the plug 60 is to remain after drilling out the excavatable material 62, the casing 64 will be configured to enable the blast to propagate from the blast holes through to the blasting void.

[0257] The broken ore can now be retrieved and the method can be repeated until the whole ore body has been mined.

[0258] Reference is made to Figures 28-32 that illustrates a system 1 for deploying an excavatable plug for creating a blasting void. The system 1 includes a plurality of elongate, rectangular-shaped (in cross-section) casing elements 2, which are configured to be interconnected with one another in an end-to-end relationship to form a continuous, substantially rigid casing 3. In Figure 28, the individual casing elements 2 can be seen arranged in general alignment and spaced apart from one another in the upper tunnel Tu. In Figure 29, the casing elements 2 can be seen connected in end-to-end relationship to form the elongate casing 3 in the upper tunnel Tu. Each of the individual casing elements 2 is, for example, about 3 metres long such that eight casing elements 2 combine to form a casing 3 having a length of about 24 metres (may typically be more when including connecting means). The modular nature of system 1 means that the number of the casing elements 2 can be varied and selected to provide a casing 3 having a desired length for a particular mining environment. System 1 further includes an apparatus 4 for positioning the casing 3 relative to the wall or face F of the unmined stope S - that is, at an interface region between the unmined stope S and the previously mined open stope So. The apparatus 4 is adapted to move the elongate casing 3 into position by moving it along the upper tunnel Tu and out over an edge of100625635665the wall or face F of the unmined stope S into the open stope So. In this regard, reference is now made to Figures 31 and 32.

[0259] As seen in Figures 31 and 32, the apparatus 4 for positioning the casing 3 includes at least one conveyor unit 5 having a bed of rollers 6 for supporting the casing elements 2 / casing 3 thereon and defining a conveyor path P for moving the casing 3. A suitable number of conveyor units 5 is selected to suit the number of casing elements 2 and / or the length of casing 3. Conveyor units 5 can be suitably placed and connected in alignment in upper tunnel Tu to support the plurality of casing elements 2 while they are aligned and interconnected with one another. In this regard, each of conveyor units 5 has a rigid frame 7 with ground-engaging skids 8 for sliding movement over the floor of the tunnel Tu. Frame 7 of each conveyor unit 5 includes connection points (e.g., via holes 9) for securely connecting or fixing the plurality of conveyor units 5 in axial alignment with one another, e.g., via connecting rods or struts (not seen). Fork-lift sleeves 10 may be provided on frame 7 of each conveyor unit 5 for lifting and transporting the units 5 to a desired location, e.g. in the upper tunnel Tu. Frame 7 of each conveyor unit 5 has a pair of upstanding lateral restraints or side stops 11 providing lateral constraint to the conveyor path P at either side of the bed of rollers 6. The side stop or restraint 11 is only shown on one side of the conveyor unit 5 in Figure 31 in order to show or reveal the bed of rollers 6.

[0260] One of casing elements 2 is shown in cross-section in Figure 32 supported on conveyor unit 5. Casing element 2 has a generally rectangular-shaped cross-sectional profile forming a rectangular channel shape with side walls 12 that extend approximately perpendicularly between side walls 13. In this example, side walls 12 have a length of about 1000 mm (corresponding to the depth dimension of the deployed casing 3) and side walls 13 have a length of about 2400 mm (corresponding to the width dimension of the deployed casing 3). However, it will be appreciated that these dimensions can vary as appropriate for the drilling and blast activities (e.g. they can be smaller or larger as required). Referring to Figure 32, the rectangular-shaped casing element 2 is supported on the bed of rollers 6 between the two side stops 11. When the casing elements 2 are in a corresponding orientation and aligned with one another along the series of conveyor units 5, they can be interconnected to form the elongate casing 3, as shown in Figure 29. To this end, the cross-sectional profile seen in Figure10062563566632 includes four round holes 14 designed for receiving connector elements for rigid interconnection of the respective casing elements 2. In this regard, in one example the connector elements (not shown) comprise cables, such as steel cables, which pass through the aligned holes 14 of each of the casing elements 2 arranged end-to-end with their end faces in abutment. After being fixed at one end of an end-most casing element 2, e.g., via an end plate (not shown), those cables (not shown) in the aligned holes 14 are tensioned to apply a force compressing the abutting end faces of all the individual casing elements 2 together, thereby to form or constitute the elongate casing 3. As will be appreciated, the cables passing through the holes 14 along the length of the casing elements 2 assist to align the casing elements 2 during preassembly of the elongate casing 3. These abutting end faces may further include complementary mating connectors 15, e.g., tongue and groove connectors, to assist alignment and registration of each of the casing elements 2 with respect to one another during their interconnection. The internal cavity 16 of each casing element 2 combine in the assembled casing 3 to define a volume V to be filled with excavatable material. Thus, it will be appreciated that in this embodiment, the casing is deployed first, followed later by a step of filling volume V with an excavatable material, thereby forming the excavatable plug.

[0261] It will be appreciated that whilst in some embodiments casing elements 2 are formed as solid (closed) sections, in other embodiments each casing element 2 can also be formed of an open framework or a truss-like structure (e.g., of a metal, such as steel, or a suitable polymer). This open framework or truss structure may then be lined or covered with sheeting to close the side walls and base to enable it to be suitably filled with the excavatable material. Alternatively, this open framework or truss structure may be filled or packed with an excavatable material, such as a foam material, that will not leak out of the framework. It will also be appreciated that the plurality of casing elements 2 need not be interconnected with one another by cables. Instead, a range of different connection types (e.g. other mechanical connections) are possible. For example, at the interface of the abutting ends of two casing elements 2, fixing plates (not shown) may be secured, e.g., via bolts, to side walls 12 and / or side walls 13 spanning the interface of the abutting ends to connect the casing elements 2 together. In an alternative100625635667arrangement, the abutting end faces of each pair of adjacent casing elements 2 may simply be bolted together.

[0262] With reference to Figures 29 and 30, after the plurality of casing elements 2 have been preassembled or interconnected with one another in fixed end-to-end relationship to form casing 3, casing 3 is moved via the positioning apparatus 4, in this case via the conveyor units 5, along the upper tunnel Tu towards the wall or face F of the unmined stope S for deployment or installation. To this end, the rollers 6 of the conveyor units 5 may be driven, e.g., by electric motor, to move the casing 3 along the conveyor path P. Alternatively, the positioning apparatus 4 may include other means, such as a cable winch, for moving (pulling) the casing 3 along the conveyor path P. Casing 3 can also be rolled or slid manually along the path P in the upper tunnel Tu.

[0263] Referring now to Figures 33 to 36, the positioning apparatus 4 of this embodiment further includes a cradle assembly 17 to assist positioning casing 3 at the interface region between the unmined stope S and the previously mined stope So prior to backfilling the previously mined stope. In this regard, cradle assembly 17 is adapted to position and / or orient casing 3 at a desired angle for drill and blast mining activities in the particular mine environment. In this regard, for example, as is best shown in Figures 35 and 36, the casing 3 must be moved and positioned at an angle substantially matching the generally vertical angle of the wall or face F of the unmined stope S and an angle a substantially matching an angle of the ore body B in the wall or face F of the unmined stope (i.e. , here at approx. 45 degrees downwards to the right). Thus, the cradle assembly 17 is adapted to assist movement and positioning of casing 3 from a substantially horizontal orientation in the upper tunnel Tu to the desired angle for drill and blast mining activities adjacent the wall or face F of the unmined stope. The angle a of the cradle assembly 17 in this embodiment is preferably adjustable via a strut 21 as will be described below. In an alternative embodiment, however, the cradle assembly 17 may simply be provided fixed at the desired angle a of the ore body B in the wall or face F of the unmined stope S.

[0264] With reference to Figs. 36 to 39, the cradle assembly 17 includes a base 18 which is secured or fixed to a floor of the upper tunnel Tu, e.g., by anchors or rock bolts R, and a generally U-shaped cradle 19 which is pivotably mounted on the base 18. The100625635668U-shaped cradle 19 is configured to hold or support the casing 3 as it is advanced from the upper tunnel Tu over the edge of the face F of the unmined stope S, as shown in Figure 33. Further, the cradle assembly 17 includes a mechanism 20 that is adapted to tilt or orient the casing 3 to a desired angle a and to lower the casing 3 to a desired position along the wall or face F of the unmined stope S, as shown in Figures 34 and 35. In this regard, the mechanism 20 includes one or more hydraulic cylinders or struts 21 adapted to pivot or to set or orient the U-shaped cradle 19 holding casing 3 to an angle a (e.g., in a range of 0 degrees to 90 degrees, and preferably in a range of about 20 degrees to about 70 degrees) about a pivot axis 22, which then corresponds to an angle of orientation a in the plane of the face F of the unmined stope S (see Figures 36 and 38). The mechanism 20 in cradle assembly 17 further includes hydraulic cylinders 23 for moving or pivoting the U-shaped cradle 19 holding the casing 3 about a pivot joint 24 to lower the casing 3 over the edge onto the wall or face F of the unmined stope S. In doing so, casing 3 may be restrained and / or lowered into its position on the wall or face F of the stope S by cables (not shown). In a mechanism 20 without the hydraulic cylinders 23, casing 3 may be lowered into its position on the wall or face F of the stope S by such cables or by other mechanical means. Referring to Figures 36 and 38, the mechanism 20 may also provide for adjusting the position of the cradle 19 in a direction of the arrows 25 to correspondingly adjust the position of casing 3 across the wall or face F of the unmined stope S. In this regard, cradle assembly 17 can be mounted on rails or tracks (not shown) for sliding or rolling movement or displacement (e.g., via an electric or hydraulic drive) laterally in a direction of arrows 25. Once casing 3 is in a desired position with an edge of one of side walls 13 adjacent or abutting the face F of the unmined stope S (see Figures 35 and 36), it can be secured in that position (e.g., by cables, chains, or the like) such that cavities 16 of each individual casing elements 2 together form or define a volume V for the excavatable material.

[0265] Similar to the earlier method, it will be appreciated from the above that an improved method of forming a blasting void when mining underground is provided. The formation of a blasting void in the backfill material, in this embodiment via the excavatable plug provides substantial advantages. One advantage is that the blasting void can be created using standard mine production drilling rigs, rather than the more specialised hard rock-type equipment and methodology (e.g. hard-rock drills, bits,100625635669cutters, specific sequences, interactions and mine operations typically required to establish the blasting void). This enables the blasting void to be established in significantly less time than would typically be the case using conventional blasting void formation methodology, such as drill and blast (i.e. burn cut), drilled / bored rise (i.e. raise bore), and box hole processes. This has significant benefits to a particular mine in terms of scheduling, production equipment availability and cost of additional equipment and contractors.

[0266] Another advantage is the reduction in mine cycle time given the reduced time in forming the blasting void and therefore the reduction in time to carry out a typical ore recovery process. Creating the blasting void is known as being a costly and time intensive part of the ore recovery process and therefore simplifying this stage of the process is greatly beneficial to the mine.

[0267] A further advantage is that the blasting void can be created without using explosives, thereby saving on the cost and time associated with blasting at this stage of the process.

[0268] Whilst the above method is described in the context of creating a blasting void during underground mining, the method has utility beyond creating blasting voids.

[0269] In another embodiment, a method for creating a non-blasting void, in this example a ventilation void, for underground mining is provided as best shown in Figures 18-22. In this embodiment, the method is similar to the first method of creating a blasting void described earlier.

[0270] For ease of explanation, the starting point for this method is an existing shaft 70 (as shown in Figure 18), e.g. a generally circular hole having a 5 m diameter and a height of 35 m, the shaft disposed in hard rock 72 and configured to allow passage of air. Over time, the shaft 70 deteriorates if left unsupported, and thus typically will require excessive rock bolting, shotcrete, and / or other stabilisers to prevent deterioration, blockage or closure of the shaft. The need to employ these stabilising techniques results in greater cost to a mine.

[0271] In accordance with this method, the shaft 70 can be backfilled with a suitable backfill material 74 as shown in Figure 19. For the present example, a paste backfill has100625635670been used. However, a person skilled in the art will appreciate that there are various suitable backfill materials that can be used. The method of this embodiment is particularly well suited for applications where a flowable backfill material is used. In order to confine the backfill material 74 to the shaft 70, the bottom of the shaft 70 is suitably blocked off to ensure that there is no leak of backfill material 74 into nearby tunnels underground.

[0272] After the backfill material 74 has cured (if required), the method moves to excavating the backfill material 74. As shown in Figure 20, a substantial portion of the backfill material 74 is excavated (e.g. drilled) out, thereby forming the ventilation void 76. Notably, in this example, an annulus of backfill material 74 remains, with this annulus of backfill material 74 configured to maintain the integrity of the ventilation void 76.

[0273] In some applications, the annulus of backfill material provides sufficient support to maintain the integrity of the ventilation void for a desired amount of time. However, for certain applications, further support may be required or desired. As shown in Figure 21 , a lining 75 is installed in the ventilation void and secured to an interior of the ventilation void 76 to maintain the integrity of the ventilation void. Any suitable securing means can be used to secure the lining 75 to the ventilation void 76. As shown in Figure 22, the lining 76 is of generally tubular form and extends the length of the shaft 70. It will be appreciated that different forms of bracing means can be used to that depicted in this example.

[0274] In another embodiment, a method for creating a non-blasting void, in this example a ventilation void, for underground mining is provided as best shown in Figures 23-27. In this embodiment, the method is very similar to the second method of creating a blasting void, using a removable or partially removable (e.g. excavatable) plug, described earlier.

[0275] For ease of explanation, the starting point for this method is an existing shaft 80 as shown in Figure 23.

[0276] In accordance with this method, an excavatable plug 84 is deployed into the shaft 80 as shown in Figure 24. The excavatable plug 84 can be of the form described100625635671earlier (in this case having excavatable material 89 encased by casing 85). In this example (and generally preferred), the excavatable plug 84 is narrower than the shaft 80.

[0277] Once deployed in the shaft, the space 83 between the plug 84 and the shaft 80 is backfilled with a suitable backfill material 87, e.g. a paste fill, thereby setting the plug 84 in place within the shaft 80 as shown in Figure 25. A person skilled in the art will appreciate that there are various suitable backfill materials that could be used. In order to confine the backfill material to the shaft 80, the bottom of the shaft is suitably blocked off to ensure that there is no leak of backfill material into nearby tunnels underground.

[0278] After the backfill material has cured (if required), the method moves to creating the ventilation void by excavating the excavatable material 89 of the plug 84 (or, depending on the plug construction, the entirety of the plug) as shown in Figure 26. In this embodiment, the excavatable material 89 of the plug 84 is drilled out, thereby creating the ventilation void 86 in the centre of the shaft 80 surrounded by an annulus of backfill material 87, with casing 85 remaining. This annulus of backfill material is configured to maintain the integrity of the ventilation void for a relatively extended period of time relative to no stabilisation of the ventilation void.

[0279] In some applications, the annulus of backfill material 87 provides sufficient support to maintain the integrity of the ventilation void 86 for a desired amount of time. However, for certain applications, further support may be required or desired. As shown in Figure 27, a lining 88 is installed in the ventilation void 86 (e.g. within casing 85) and secured to an interior of the casing 85 to maintain the integrity of the ventilation void 86. Any suitable securing means can be used to secure the lining to the ventilation void. It will be appreciated that different forms of bracing means can be used to that depicted in this example.

[0280] These methods for forming non-blasting voids have significant advantages for the mine in terms of speed of installation and enabling the shaft to be supported without putting mining workers into the shaft to insert stabilisers, such as rock bolts.

[0281] Thus, as shown by the above method, the excavatable plug can be deployed in both hard rock and backfill settings. In certain examples, the excavatable plug could be100625635672employed in other steps of the processes described herein, such as being used in blast holes, or in blast or void holes that are to be excavated at a later point in time. It is envisaged that when used in hard rock applications, the excavatable plug could be suitably deployed in multiple locations along an ore body to be mined. For example, in an open stoping or long hole stoping process, multiple longitudinally spaced blasting voids may be formed (using conventional techniques) in a single pass along the ore body, and then each of the blasting voids temporarily closed using the excavatable plugs. One embodiment of this is provided in Figure 40, which illustrates an ore drive 90 (in plan view) with a plurality of longitudinally spaced plugs 92 disposed at an approximate boundary of respective stope sections of an ore body. As each stope section is mined in sequence, each next stope to be mined will already be furnished with an excavatable plug, meaning that production drilling rigs already in the drive can right away drill out the excavatable plug, drill the blast holes, and allow for blasting of the stope to take place. This can provide significant cost and time saving for a mine, whereby it is possible to essentially establish all the necessary blasting voids in a reduced number of passes, and therefore not need to continually re-deploy the hard rock drilling equipment. It will be appreciated that along similar lines, instead of the excavatable plug, the simpler backfill methodology of the first non-blasting void embodiment can also be employed in much the same way and provide many of the same advantages as the use of the excavatable plug.

[0282] It will be understood that, in general, the location of the blasting and / or nonblasting voids is such that it enables total flexibility in drill and blast design. This is particularly advantageous due to varying geometries, geological conditions and site conditions found throughout the underground mining industry as well as the different drill and blast sequences and design. Examples of varying void / plug placement may include the plug sitting on the foot wall of an open stope, central in a shaft with a suitable annulus surrounding to plug as required by geotechnical conditions or at an optimal location for drill and blast mining.

[0283] It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

Claims

100625635673CLAIMS1. A method of creating one or more blasting voids during underground mining, said one or more blasting voids configured to allow expansion of blasted material during a stope firing, the method including:drilling, in a backfill material near an interface between the backfill material and an unexcavated stope, a plurality of holes extending into the backfill material, said plurality of holes disposed in a predetermined pattern such that the plurality of holes define one or more blasting voids,wherein at least one of the one or more blasting voids is a continuous or substantially continuous void having, in plan-view cross-section, a width greater than a depth.

2. The method of claim 1 , wherein the backfill material is a flowable backfill material.

3. The method of claim 1 or 2, wherein two or more of the plurality of holes are disposed in close proximity to one another such that said two or more holes together define one of the one or more blasting voids.

4. The method of any one of the preceding claims, wherein said predetermined pattern includes arranging two or more of the plurality of holes near to one another and / or arranging two or more of the plurality of holes such that they intersect with one another.

5. The method of claim 4, wherein said predetermined pattern includes a substantially linear row of holes adjacent to one another, wherein said substantially linear row of holes are arranged substantially in a transverse direction, which is perpendicular to a longitudinal direction, said longitudinal direction coinciding with a general direction of an underground ore drive or the strike of the ore body, and said transverse direction is parallel to a height direction of the unexcavated stope.1006256356746. The method of claim 5, wherein said predetermined pattern includes a plurality of substantially linear row of holes, each row being spaced apart from one another along the longitudinal direction.

7. The method of claim 6, wherein said predetermined pattern includes a staggered arrangement.

8. The method of claim 7, wherein said plurality of substantially linear row of holes includes a first substantially linear row of holes and a second substantially linear row of holes spaced apart from the first substantially linear row of holes, wherein said first substantially linear row of holes is substantially parallel with the second substantially linear row of holes.

9. The method of claim 8, wherein said plurality of substantially linear row of holes includes a first substantially linear row of holes and a second substantially linear row of holes spaced apart from the first substantially linear row of holes, wherein said first substantially linear row of holes and said second substantially linear row of holes are angled with respect to each other.

10. The method of claim 8, wherein one or both of said first substantially linear row of holes and said second substantially linear row of holes are angled towards the interface between the backfill material and the unexcavated stope.

11. The method of claim 8, wherein one or both of said first substantially linear row of holes and said second substantially linear row of holes are angled away from the interface between the backfill material and the unexcavated stope.

12. The method of claim 10 or 11 , wherein said first substantially linear row of holes and said second substantially linear row of holes are arranged such that one or more distal ends of the holes of the first substantially linear row of holes are positioned closer to one or more distal ends of the holes of the second substantially linear row of holes and / or such that spacing between adjacent distal ends of the holes is selected to be sufficiently small that the holes collectively establish a substantially continuous blasting void at or near the interface between the backfill material and the unexcavated stope.10062563567513. The method of claim 12, wherein one or more holes of the first substantially linear row of holes and one or more holes of the second substantially linear row of holes are oriented such that the respective distal ends of the holes converge toward one another.

14. The method of any one of the preceding claims, wherein the blasting void has a width to depth ratio of between about 1.1:1 and about 75: 1.

15. The method of any one of the preceding claims, wherein at least one of the one or more blasting voids is configured to facilitate expansion of blasted material from the unexcavated stope towards the blasting void in a generally forward direction.

16. The method of claim 15, wherein the plurality of holes defining the blasting void are positioned forward of blast holes in the unexcavated stope such that blasted material expands in the generally forward direction toward the blasting void.

17. The method of any one of the preceding claims, wherein said plurality of holes are of greater diameter and / or width / depth relative to holes typically formed in long hole slot / rise methodologies.

18. The method of claim 17, wherein one or more of the plurality of drilled holes have a diameter of greater than 204 mm.

19. The method of claim 17, wherein one or more of the plurality of drilled holes have a diameter of less than or equal to 204 mm.

20. The method of any one of the preceding claims, wherein said drilling the plurality of holes includes drilling the plurality of holes using soft rock drilling methodology.

21. The method of any one of the preceding claims, wherein said one or more blasting voids is created without the use of explosives.

22. The method of any one of the preceding claims, wherein drilling of said plurality of holes is conducted by a standard production drill rig.

23. A method of mining an unexcavated stope, the method including:100625635676creating one or more blasting voids by the method of any one of claims 1 to 22;creating a plurality of blast holes in the unexcavated stope near the interface between the backfill material and the unexcavated stope;loading the plurality of blast holes with explosives and blasting towards the one or more blasting voids previously established in the backfill material to form an open stope; andremoving broken ore from the open stope.

24. The method of claim 23, wherein the method further includes backfilling the open stope with backfill material;after said backfilling, repeating the steps of:creating one or more blasting voids in the backfill material near an interface between the backfill material and a next unexcavated stope to mine, creating a plurality of blast holes in the next unexcavated stope near the interface between the backfill material and the next unexcavated stope, loading the plurality of blast holes with explosives and blasting towards the one or more blasting voids established in the backfill material to form an open stope, and removing broken ore from the open stope.

25. A drill bit for use in the method of any one of the preceding claims, said drill bit used for creating the plurality of holes extending into the backfill material that define the one or more blasting voids.

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