A method for supporting an anchor cable at a specified position in a reinforced rock mass

Abstract

The application discloses a method for reinforcing the inside of a specified position of a rock mass, drilling a borehole at a roadway free surface, penetrating into a broken surrounding rock, and reaching a specified depth of the surrounding rock according to design requirements, determining a support limit through production exploration results and drilling feedback information, determining a support section length and a hole section length through the borehole depth and the support limit, shearing a support anchor slightly longer than the support section length, pushing a partition device, the support anchor and a grouting pipe into the borehole through a pushing anchor until the support anchor and the grouting pipe reach the bottom of the borehole, and finally pulling out the pushing anchor. The cement mortar is filled to the support limit while pulling out the grouting pipe, and then the grouting is stopped. The application has the advantages of high utilization rate of the anchor, reliable quality of the anchor, and safety of mining in a stope.

Description

Technical Field

[0001] This invention belongs to the field of rock mass support and relates to a method for reinforcing anchor cable support at a specified location inside a rock mass, which is particularly suitable for rock mass support during mining of unstable ore bodies in the hanging wall. Background Technology

[0002] For underground ore bodies with poor stability of the hanging wall, support work is essential for safe and efficient ore extraction. Currently, commonly used underground support methods mainly include concrete support, shotcrete support, steel arch support, and bolt / cable anchor support. Concrete support, shotcrete support, and steel arch support are primarily used to support the surface of the surrounding rock, preventing weathering and deformation. Bolt / cable anchor support reinforces the surrounding rock through suspension and compression arching. For thin ore bodies, all of the above support methods are applicable. For thick ore bodies, pre-support with anchor cables is typically used to reinforce the unstable hanging wall.

[0003] Currently, the common method for anchor cable pre-support is to drill anchor cable holes in the mining roadway to the deep, unstable surrounding rock, and then push the anchor cables into the holes for full-hole support. For example, existing patent CN115217474B discloses a top-up layered filling mining method for thick, fractured ore bodies using long anchor cables for pre-support. This method involves vertically constructing long anchor cables after mining to support the roof and upper layers. The long anchor cable support construction steps include determining anchor cable and grouting parameters, temporary support, drilling, and grouting after the anchor cables are delivered to the bottom of the hole. Existing patent CN120007258B discloses a top-up fan-shaped medium-deep hole stage filling mining method for steeply inclined fractured ore bodies. This method uses grouting long anchor cables for pre-reinforcement of the hanging wall surrounding rock. By injecting cement grout under high pressure into the surrounding rock fissures, combined with the suspension effect of the long anchor cables, the stability of the hanging wall surrounding rock in the stope can be effectively improved. Existing patent CN115773113B discloses a mining method for steeply inclined, fractured, thick ore bodies. In this method, multiple rows of upward-facing long anchor cables with dip angles equal to the ore body are constructed vertically upward in the external roadway near the wall of the ore body, perpendicular to the ore body's strike. In the external roadway near the wall of the ore body, multiple rows of downward-facing long anchor cables are constructed vertically downward in the external roadway, perpendicular to the ore body's strike. In the drilling roadway, upward-facing long anchor cables are constructed vertically upward in the internal roadway, perpendicular to the ore body's strike, to support and reinforce the fractured surrounding rock of the wall and the roof of the stope. The long anchor cable support construction steps include: constructing anchor cable holes, flushing anchor cable holes, installing anchor cables, and grouting.

[0004] The advantages of the above-mentioned support method are that it provides full-section support and good stability. The disadvantages are that the anchor cables reinforce both the fractured surrounding rock and the stable ore body, resulting in low anchor cable utilization. Furthermore, after the stable ore body is mined out, a large number of suspended anchor cables will be formed, with some even having boulders hanging from them, causing serious safety hazards. Some anchor cables may also break and scatter into the ore, making ore transportation and subsequent beneficiation difficult.

[0005] Therefore, this traditional anchor cable support method is no longer suitable for mining ore bodies with unstable hanging wall rock. To address this, the present invention creates a novel anchor cable support method for reinforcing designated locations within the rock mass, aiming to comprehensively solve the aforementioned problems. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a safe, reliable, economical, and efficient method for anchor cable support at designated locations within a rock mass. This method is suitable for reinforcing unstable surrounding rock in the hanging wall of medium-thick or thick ore bodies. It involves anchor cable support at designated locations through mining roadways to reinforce the fractured surrounding rock in the hanging wall, achieving pre-support of the fractured surrounding rock before ore body mining, ensuring the safety of subsequent mining operations, and ultimately achieving economical and efficient mining.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for reinforcing anchor cable support at a designated location within a rock mass includes the following steps: 1) First, drill holes at the free face of the roadway, pass through the ore body into the broken surrounding rock, and reach the specified depth of the surrounding rock according to the design requirements; 2) Determine the support boundary based on production exploration results and drilling feedback information, and determine the length of the support section and the length of the empty hole section based on the drilling depth and support boundary. 3) Cut a section of support anchor cable slightly longer than the length of the support section, push the support anchor cable into the borehole, align the tail of the support anchor cable with the borehole opening, then connect the tail of the support anchor cable to the opening on the partition device, and install the partition device at the borehole opening. Then connect the push anchor cable to the lower opening of the partition device, and at the same time pass the grouting pipe through the partition device, with the length of the passage being basically consistent with the length of the support anchor cable. Using the rigidity of the anchor cable, push the push anchor cable, partition device, support anchor cable, and grouting pipe together into the borehole until the support anchor cable and grouting pipe reach the bottom of the borehole. Finally, pull out the push anchor cable, leaving the partition device, support anchor cable, and grouting pipe together in the hole. The partition device is H-shaped, with an outwardly extending elastic plate at its bottom. The upper and lower sides of the partition plate in the middle of the partition device are provided with connecting parts for connecting with the support anchor cable and the push anchor cable. The elastic plate is provided with two through holes, one for the grouting pipe to pass through and the other for grouting venting.

[0008] 4) Start the grouting equipment and grout while pulling it out of the borehole until the cement mortar fills the support boundary. Then stop grouting and pull out the grouting pipe. Furthermore, the support boundary usually refers to the ore-rock boundary line, that is, the upper boundary line of the stope; the support section length refers to the distance from the support boundary to the bottom of the borehole; and the empty hole section length refers to the distance from the support boundary to the borehole opening.

[0009] Furthermore, the upper opening diameter of the partition device is slightly larger than the anchor cable diameter. After the elastic plate is installed at the bottom of the partition device, the lower opening diameter is slightly larger than the drill hole diameter in its natural state. After being inserted into the drill hole, the elastic plate exerts pressure on the drill hole, making the partition device only able to move forward and not backward.

[0010] Preferably, the connecting component is a pre-drilled internal threaded hole, and the support anchor cable and the push anchor cable are connected to the isolation device at their ends by a pre-installed connecting rod with external threads.

[0011] Furthermore, the cement mortar possesses the characteristics of non-segregation, non-bleeding, and moderate fluidity, preventing grout leakage and blockage of vent holes. Preferably, 425 cement and fine sand are used, with a cement-sand ratio of 1:1 to 1:1.5 and a water-cement ratio of 0.40 to 0.45.

[0012] Beneficial effects The technical solution of this invention produces the following technical effects: First, the anchor cable utilization rate is high. By using the isolation device, only the fractured hanging wall rock is supported, which makes full use of the anchor cables and greatly reduces the amount of anchor cables and cement mortar used. Secondly, the anchor cable is of reliable quality. The isolation device not only pushes the anchor cable forward, but also has a "one-way forward, no-backward" characteristic, which can effectively fix the anchor cable and prevent cement mortar loss, ensuring strength and quality. Third, effective utilization of boreholes. The remaining empty sections after support is completed can be used as fan-shaped blast holes for caving ore, making full use of the boreholes; Fourth, the mining area is safe and stable. After the mining is completed, the suspension of anchor cables on the top of the mining area and the hanging of anchor cables and rocks are avoided. At the same time, the breakage of anchor cables and their scattering into the ore will also avoid difficulties in ore transportation and subsequent ore beneficiation. Attached Figure Description

[0013] Figure 1 This is a cross-sectional view of the present invention.

[0014] In the diagram: 1-Open face of the roadway; 2-Borehole; 2-1-Borehole bottom; 2-2-Borehole opening; 3-Support boundary; 4-Support section; 5-Borehole section; 6-Cement mortar; 7-Support anchor cable; 8-Isolation device; 8-1-Upper opening of isolation device; 8-2-Isolation plate; 8-3-Lower opening of isolation device; 8-4-Elastic plate; 8-5-Grouting vent hole; 8-6-Grouting pipe hole; 9-Pushing anchor cable; 10-Grouting pipe. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0016] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0017] Furthermore, in the description of this invention, unless otherwise stated, "multiple", "multiple roots", and "multiple groups" mean two or more, and "several", "several roots", and "several groups" mean one or more.

[0018] like Figure 1 As shown, the present invention provides a method for reinforcing anchor cable support at a designated location within a rock mass, comprising the following steps: S1, firstly, drill holes at the free face of the roadway, pass through the ore body into the fractured surrounding rock, and reach the specified depth of the surrounding rock according to the design requirements; It should be noted that the drilling method usually depends on the hardness and degree of fracturing of the rock strata, as well as the required drilling depth and diameter. Equipment such as anchor drilling rigs, down-the-hole drilling rigs, and geological drilling rigs can be used for drilling. During the drilling process in fractured surrounding rock, measures such as strong air slag removal or clean water circulation can be used to clean the borehole wall to maintain its stability.

[0019] Generally, drilling can be stopped after penetrating the fractured surrounding rock adjacent to the ore body and entering the stable surrounding rock for 0.5-1m. The drilling depth is generally 8-12m, with 4-6m for the surrounding rock section and 4-6m for the ore body section.

[0020] S2, determine the support boundary 3 based on production exploration results and drilling feedback information, and determine the length of the support section 4 and the length of the empty section 5 based on the drilling depth and support boundary; It should be noted that the support boundary 3 mentioned in this invention generally refers to the ore-rock boundary line, that is, the boundary line between the fractured surrounding rock in the hanging wall and the ore body. The rock properties being drilled can be determined by the results of geological exploration in the early stages of the design phase, combined with changes in various parameters of the drilling rig during construction (such as drilling speed, sound, and expelled rock dust), and the experience of the operators. These parameters will change significantly when drilling from the ore body into the surrounding rock, or from the fractured zone into stable rock. When drilling near the design boundary and observing a sudden change in parameters, the accurate location of the support boundary can be confirmed.

[0021] In some embodiments, the drilling speed of the drilling rig changes significantly when the drill bit enters the fractured surrounding rock from the ore body or from the relatively stable rock into the fractured zone, and the location of the support boundary is determined by the change in speed.

[0022] Sudden increase in drilling speed: If the surrounding rock is more fractured than the ore body, the drilling resistance decreases and the drilling speed will suddenly increase, and there may even be a feeling of the drill falling off.

[0023] A sudden decrease in drilling speed: If the surrounding rock is hard and the ore body is soft, the drilling speed will decrease significantly, and the drill rod will rebound more violently.

[0024] In some embodiments, the location of the support boundary can be determined by observing changes in the color or shape of the rock powder discharged from the borehole. For example, if the ore and the surrounding rock are different colors, the point of color change is the ore-rock boundary. Furthermore, if the drilled material is "mud" or "powdered" debris, it indicates the entry into a fractured zone; if the drilled material is "pea-shaped" or "flaky" rock cuttings, it indicates a relatively intact rock mass. When the color or state of the rock powder changes, the borehole depth at that time is measured, and this depth is the approximate location of support boundary 3.

[0025] In some embodiments, changes in wind pressure or water pressure can also be observed. When the borehole enters the fractured surrounding rock with developed fissures from the relatively dense rock mass, the flushing water pressure drops suddenly or the slag discharge air pressure decreases suddenly. The depth of the point of change is the support boundary position.

[0026] Furthermore, once the borehole depth and support boundary are determined, the lengths of the support section and the empty borehole section can be determined. The length of the support section 4 refers to the distance from the support boundary 3 to the bottom of the borehole 2-1; the length of the empty borehole section 5 refers to the distance from the support boundary 3 to the borehole opening 2-2.

[0027] S3, cut a support anchor cable slightly longer than the support section length, push the support anchor cable into the borehole, align the tail of the support anchor cable with the borehole opening, then connect the tail of the support anchor cable to the opening on the partition device, and install the partition device at the borehole opening. Then connect the push anchor cable to the lower opening of the partition device, and at the same time pass the grouting pipe through the partition device, with the length of the passage being basically consistent with the length of the support anchor cable. Using the rigidity of the anchor cable, push the push anchor cable, partition device, support anchor cable, and grouting pipe together into the borehole until the support anchor cable and grouting pipe reach the bottom of the borehole. Finally, pull out the push anchor cable, leaving the partition device, support anchor cable, and grouting pipe together in the hole. The partition device 8 is H-shaped, with an outwardly extending elastic plate 8-4 at its bottom. The partition plate 8-2 in the middle of the partition device has connecting parts on both the upper and lower sides for connecting with the support anchor cable 7 and the push anchor cable 9. The elastic plate 8-4 has two through holes: one is a grouting venting hole 8-5 for grouting venting, and the other is a grouting pipe hole 8-6 for the grouting pipe 10 to pass through.

[0028] Furthermore, the diameter of the upper opening 8-1 of the partition device is slightly larger than the diameter of the anchor cable. After the elastic plate is installed at the bottom of the partition device, the diameter of its lower opening 8-3 is slightly larger than the diameter of the drill hole 2 in its natural state. After being inserted into the drill hole, the elastic plate 3 exerts pressure on the drill hole 2, so that the partition device 8 can only move forward and cannot move backward.

[0029] Preferably, the connecting component is a pre-reserved internal threaded hole, and the support anchor cable 7 and the push anchor cable 9 are connected to the isolation device 8 at their ends by a pre-installed connecting rod with external threads, so that quick installation and disassembly can be achieved through the threaded connection.

[0030] S4, start the grouting equipment, and grout while pulling it out of the borehole until the cement mortar fills the support boundary, then stop grouting and pull out the grouting pipe; Furthermore, the cement mortar described in this application has the characteristics of not segregating, not bleeding, and having moderate fluidity, and will not leak or clog vent holes. Preferably, the cement mortar uses 425 cement and fine sand, with a cement-sand ratio of 1:1 to 1:1.5 and a water-cement ratio of 0.40 to 0.45.

[0031] This application employs a method of grouting while simultaneously pulling the grout pipe outwards from the borehole, ensuring uniform pressure distribution and dense grout filling. By inserting the grouting pipe directly to the bottom of the hole, grout is injected from the deepest point and gradually pushed outwards. The grouting pipe outlet remains buried within the injected grout, guaranteeing complete filling of the space in front of the pipe and preventing voids at the bottom of the hole. Furthermore, as the pipe is pulled outwards, pressure remains applied to unfilled sections, facilitating grout penetration into the micro-fractures of the fractured surrounding rock and improving its integrity and strength. Simultaneously, controlling the speed and timing of pipe withdrawal near the support boundary—for example, slowly pulling out the pipe and allowing the grout near the borehole to solidify before complete withdrawal—allows for precise segmented grouting, ensuring grouting is only performed in the fractured surrounding rock section and conserving materials.

[0032] In this invention, the partition device 8 integrates multiple functions such as connection, pushing, positioning, and self-locking. Connecting components are provided on both the upper and lower surfaces of the partition, making it the core of the entire device. One end connects to the support anchor cable to be permanently installed, and the other end connects to the pushing anchor cable used for construction. The thrust applied by the pushing anchor cable is evenly transmitted to the upper support anchor cable through the partition device, effectively transferring the stiffness of the pushing anchor cable to the support anchor cable. This design solves the problem of the support anchor cable being difficult to push directly within the borehole.

[0033] The elastic plate at the bottom has a one-way self-locking function to achieve the function of "only moving forward and not backward", which ensures that the isolation device and support anchor cable will not be pulled out when the push anchor cable is pulled out, thus ensuring the accurate positioning of the final support structure.

[0034] Furthermore, the geometric features of the H-shaped structure of the partition device enable it to have positioning and guiding functions. During the pushing process, the columnar shape of the partition device, especially with the elastic plate, can, to a certain extent, center itself and the connected anchor cable in the borehole, preventing the anchor cable from sticking tightly to the borehole wall.

[0035] The following section combines practical mine applications and related information. Figure 1 The anchoring support method of the present invention will be further described.

[0036] The average thickness of the ore body in a copper mine in China is 40m, with a dip angle of 63-80°. It is mainly composed of steeply dipping, thick ore bodies. The mining conditions of the ore bodies in the mine are complex. The hanging wall is a Class V carbonaceous slate, while the ore body is a Class III rock body. The footwall is a Class IV tuff rock body. The overall stability of the ore and rock is unstable. The ore and rock in the mine are well-developed joints and relatively broken. The hanging wall is a Class V carbonaceous slate. Mining disturbance can easily cause local collapses, which poses challenges and difficulties to safe production.

[0037] like Figure 1 As shown in the figure, an embodiment of the present invention provides a method for reinforcing anchor cable support at a designated location inside a rock mass, comprising the following steps: 1) A Cabletec LC anchor trolley was used to drill borehole 2 on the free face 1 of the roadway. The borehole diameter was 64mm. The borehole penetrated the ore body and entered the fractured surrounding rock. According to the design requirements, the borehole reached the specified depth of the surrounding rock, and the drilling depth was 10m. 2) The support boundary 3 is determined based on the production exploration results and drilling feedback information. The length of the support section 4 is determined to be 6m and the length of the empty section 5 is determined to be 4m based on the drilling depth and the support boundary 3. The support boundary 3 usually refers to the ore-rock boundary line, which is also the upper boundary line of the mining area; The length of the support section 4 refers to the distance from the support boundary 3 to the bottom of the borehole 2-1, which is 6m. The length of the hollow section 5 refers to the distance from the support boundary 3 to the borehole opening 2-2, which is 4m.

[0038] 3) Install the support anchor cable 7 using the Cabletec LC anchor cable trolley installation arm. Cut a section of support anchor cable 7 slightly longer than the support section length. Push the support anchor cable 7 into borehole 2, aligning the tail of the support anchor cable 7 with the borehole opening 2-2. Then, insert the tail of the support anchor cable 7 into the upper opening 8-1 of the partition device and install the partition device 8 at the borehole opening 2-2. Then, insert the push anchor cable 9 into the lower opening 8-3 of the partition device. At the same time, pass the grouting pipe 10 through the elastic plate 8-4, with the length of the passage basically consistent with the length of the support anchor cable. Then, using the rigidity of the anchor cable, push the push anchor cable 9, the partition device 8, the support anchor cable 7, and the grouting pipe 10 together into borehole 2 until the support anchor cable 7 and the grouting pipe reach the bottom 2-1 of the borehole. Finally, pull out the push anchor cable 9, leaving the partition device 8, the support anchor cable 7, and the grouting pipe 10 inside borehole 2.

[0039] 4) The Cabletec LC anchor trolley comes with a grouting system that can automatically add cement to make cement mortar. Each mixing takes about 15 minutes before grouting can be carried out. Start the automatic grouting system and slowly withdraw the grouting pipe until the cement mortar 6 fills the support boundary 3. Then turn off the automatic grouting system and withdraw the grouting pipe. This invention is applicable to reinforcing unstable surrounding rock in the hanging wall of medium-thick or thick ore bodies. Compared with traditional pre-support methods, this support method is economical, efficient, safe, and reliable. It uses anchor cables to support designated locations within the surrounding rock through mining roadways, reinforcing the fractured surrounding rock in the hanging wall of the ore body. This achieves pre-support of the fractured surrounding rock before ore body mining, ensuring the safety of subsequent mining and ultimately achieving economical and efficient mining.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for reinforcing anchor cable support at a designated location within a rock mass, characterized in that, Includes the following steps: 1) First, drill holes at the free face of the roadway, pass through the ore body into the broken surrounding rock, and reach the specified depth of the surrounding rock according to the design requirements; 2) Determine the support boundary based on production exploration results and drilling feedback information, and determine the length of the support section and the length of the empty hole section based on the drilling depth and support boundary. 3) Cut a section of support anchor cable slightly longer than the length of the support section, push the support anchor cable into the borehole, align the tail of the support anchor cable with the borehole opening, then connect the tail of the support anchor cable to the opening on the partition device, and install the partition device at the borehole opening. Then connect the push anchor cable to the lower opening of the partition device, and at the same time pass the grouting pipe through the partition device, with the length of the passage being basically consistent with the length of the support anchor cable. Using the rigidity of the anchor cable, push the push anchor cable, partition device, support anchor cable, and grouting pipe together into the borehole until the support anchor cable and grouting pipe reach the bottom of the borehole. Finally, pull out the push anchor cable, leaving the partition device, support anchor cable, and grouting pipe together in the hole. The partition device is H-shaped, with an outwardly extending elastic plate at its bottom. The upper and lower sides of the partition plate in the middle of the partition device are provided with connecting parts for connecting with the support anchor cable and the push anchor cable. The elastic plate is provided with two through holes, one for the grouting pipe to pass through and the other for grouting venting. 4) Start the grouting equipment and grout while pulling it out of the borehole until the cement mortar fills the support boundary. Then stop grouting and pull out the grouting pipe.

2. The method for anchor cable support at a designated location within a rock mass according to claim 1, characterized in that: The support boundary usually refers to the ore-rock boundary line, that is, the boundary line between the fractured surrounding rock in the hanging wall and the ore body; the support section length refers to the distance from the support boundary to the bottom of the borehole; the empty hole section length refers to the distance from the support boundary to the borehole opening.

3. The method for anchor cable support at a designated location within a rock mass according to claim 1, characterized in that: The upper opening diameter of the partition device is slightly larger than the anchor cable diameter. After the elastic plate is installed at the bottom of the partition device, the lower opening diameter is slightly larger than the drill hole diameter in its natural state. After being inserted into the drill hole, the elastic plate exerts pressure on the drill hole, making the partition device only able to move forward and not backward.

4. The method for anchor cable support at a designated location within a rock mass according to claim 1, characterized in that: Preferably, the connecting component is a pre-drilled internal threaded hole, and the support anchor cable and the push anchor cable are connected to the isolation device at their ends by a pre-installed connecting rod with external threads.

5. The method for reinforcing anchor cable support at a designated location within a rock mass according to claim 1, characterized in that: The cement mortar is characterized by non-segregation, non-bleeding, and moderate fluidity, and will not leak or clog the vent holes.

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