Consolidation system

Abstract

A system for consolidation of tailings, the system comprising a vertically-impermeable geocomposite drainage layer arrangeable in use between a first layer of tailings material and a second, lower, layer of tailings material.

Description

CONSOLIDATION SYSTEMFIELD

[0001] The present disclosure relates to consolidation systems. More particularly, the present disclosure relates to drainage system and associated methods for consolidation of mining tailings.BACKGROUND

[0002] In mining, proper handling of tailings to reduce negative environmental impacts is a significant challenge. Generally, dealing with tailings requires time for drainage, such that solid material is separated from water, thereby allowing consolidation. Effective drainage allows water to be collected and safely handled, while drainage and consolidation of the solid component of the tailings increases stability and reduces the potential for disastrous failure of tailing containment structures such as dams, ponds and the like. Traditional tailings drainage is performed using sand, stone and pipes, and requires thick layers of granular materials to allow gravity to remove water from tailings. A traditional tailings drainage system of this nature is shown in Figure 1 . In Figure 1 , the granular material 7 is shown in layers. The layers of granular material 7 are provided between layers of tailings material 6. Water is shown schematically moving down through the layers of tailings material 6 and the layers of granular material 7, as indicated by the arrows. The Figure 1 shows the tailings material contained by a dam structure D.

[0003] For typical tailings compositions, for example material with 70 to 400 micron particle size with over 80% of the particles being of less than 150 micron particle size, and the material having water content 30 to 80%, drainage and consolidation of tailings using a traditional system as showing in Figure 1 is costly. This is because significant volumes of granular material are required, and significant time is needed for both the installation of the drainage structure and for drainage and consolidation to take place.

[0004] ON 115 875 948 A describes a tailing drying method and device in which a waterresisting layer is laid in a water-permeable silo, high-water-content tailings are conveyed into the water-permeable silo, water in the tailings is removed through water-permeable silo body leakage and airing evaporation for multiple days, feeding is carried out at least once, water- permeable silo body permeation and airing evaporation for multiple days of one cycle are carried out, the water-resisting layer is laid till the dehydrated tailings are accumulated to the preset thickness, and the process is repeated. The feeding and dewatering processes are circularly and repeatedly carried out among a plurality of permeable silos.

[0005] Example embodiments described herein aim to address at least one of the issues identified, or other related issues in the field as will become apparent from the disclosure.SUMMARY

[0006] According to the present disclosure there are provided systems and methods as set out in the appended independent claims. Other features will be apparent from the dependent claims, and the description which follows.

[0007] In one example, there is provided a system for consolidation of tailings, the system comprising a vertically-impermeable geocomposite drainage layer arrangeable in use between a first layer of tailings material and a second, lower, layer of tailings material.

[0008] In one example there is provided: a tailings consolidation system comprising: a first layer of tailings material above a second layer of tailings material and separated therefrom by a vertically-impermeable geocomposite drainage layer.

[0009] Suitably, the vertically-impermeable drainage layer comprises a geocomposite layer, for example a layer including a vertically-impermeable barrier. In one example the geocomposite layer comprises a vertically-impermeable core across which collected water flows in-plane, such as towards an outflow, but across which water is unable to pass from above to below.

[0010] The vertically-impermeable drainage layer is, in example embodiments, preventing vertical movement of water between the first layer and the second layer of tailings material, preventing re-saturation of the second layer by stopping water moving down from above. The geocomposite drainage layer provides an efficient in-plane flow for collected water to move through the system such as to an outflow. These features combine to reduce the time taken to drain and consolidate the tailings material. Furthermore, capillary movement of water from the layer below the vertically-impermeable layer and into the layer above is also prevented, which may be particularly important when the tailings drainage system is being installed and there is pressure acting on the tailings material from the deposition of more such material.

[0011] In one example, the system comprises a third layer of tailings material below the second layer of tailings material and separated therefrom by a vertically-impermeable geocomposite drainage layer.

[0012] In one example, the system comprises a fourth layer of tailings material below the third layer of tailings material and separated therefrom by a vertically-impermeable geocomposite drainage layer. Advantageously, building up the tailings material in a plurality of layers, means that accelerated drainage and consolidation can be achieved even for large volume of tailings material I large depth to be drained. Correspondingly, achieving consolidation quickly means that a greater volume of tailings material can be handled in an area of smaller overall footprint.

[0013] The depth of tailings layers in a particular installation is for example calculated according to the desired drainage rate of tailings drainage system, and the properties of the tailings to be drained. This includes, particle size distribution, water content and permeability ofthe tailings material. Smaller particle size tailings and faster drainage require closer vertical spacing. In one example, the vertical spacing between the vertically-impermeable layer(s) is between 0.5m and 10m. In one example, the system is built up in layers to more than 80m in height, for example up to 100m. Quicker drainage of a large depth of tailings material reduces the risk of tailings liquefaction and makes the tailings drainage system safer by reducing the pressure on an associated tailings containment structure such as a dam.

[0014] In one example, the system is associated with a tailings containment structure.

[0015] In one example, the tailings containment structure comprises vertically-impermeable drainage layer at a lower portion thereof. In one example, the tailings containment structure comprises vertically-impermeable drainage layer below the lowermost layer of tailings, for example as its lowermost layer. Advantageously, separating tailings from an underlying substrate makes it easier to manage the outflow from the system overall.

[0016] In one example, the tailings containment structure comprises a dam.

[0017] In one example, the system comprises a tailings containment structure with an outflow, with a fluid flow path from the vertically-impermeable drainage layer(s) such that water passing from the tailings into the drainage layer(s) is arranged to flow from the tailings containment structure at an outflow. In one example, the tailings containment structure comprises a water storage reservoir between the system and the outflow, to store or otherwise buffer water moving from the tailings material to the outflow. By provision of a water storage reservoir, the tailings containment structure serves the secondary purpose of aiding water management for the area in which it is installed.

[0018] In one example, the tailings containment structure comprises a sectional consolidation arrangement. In one example, the containment structure comprises a first consolidation system and a second consolidation system. Advantageously, a sectional consolidation arrangement allows a second system to be added later to an earlier-built one, such as when sufficient consolidation has been achieved for the tailings material drained by the first system.

[0019] In example, the system comprises a plurality of sections. In one example, the sections are separated by water-impermeable drainage layers. In this way, water cannot move from the relatively drier section to re-wet a previously consolidated section.

[0020] In one example, the tailings containment structure comprises a water-impermeable drainage layer on the face of the dam, such that water in use flows across said layer ratherthan down the face of the underlying dam structure.

[0021] In one example, the tailings containment structure provides an in-plane flow path along the vertically-impermeable drainage layer(s) that separate the layers of tailing material to the outflow. In one example, the tailings containment structure provides an in-plane flow path along the vertically-impermeable drainage layer(s) that separate the layers of tailing material to thevertically-impermeable drainage layer(s) between a first system and a second system. In this way, the drainage layers provide an effective route for water from the tailings material to be drained from the system.

[0022] In one example, the tailings containment structure provides in-plane flow path from the vertically-impermeable drainage layer(s) that separate the layers of tailings material to the water- impermeable drainage layer on the face of the dam. In one example, the dam and the outflow associated therewith are at a lower end of the tailings containment structure. In one example, the outflow is provided below, such as downstream of the dam. In a separate example, the outflow is located away from the dam, such that water does not pass from the system under or through the dam.

[0023] In one example, the tailings containment structure comprises a second consolidation system added to an earlier-built first consolidation system. For example, added alongside. For example, added adjacent to, such as horizontally adjacent to. For example, added so as not to overlie, or only partially overlie such as on, or only on, a side portion thereof. In one example, the earlier-built first consolidation system comprises tailings material that is relatively drier than the second system. In one example, the earlier-built first consolidation system comprises tailings material that is relatively more consolidated than the tailings material of the second consolidation system.

[0024] In one example, the tailings containment structure comprises a water-impermeable drainage layer between a second system and the earlier-built first system. In one example, the tailings containment structure comprises a water-impermeable drainage layer laid on the earlier- build first consolidation system. That is, a water-impermeable drainage layer in use prevents movement of water between the first and second consolidation systems, and for example allows water to drain therefrom to an outflow.

[0025] In one example, a third and optionally further consolidation systems are added to earlier-built first and second consolidation systems. In one example, the third consolidation system has corresponding features to the second, as the second does to the first, and so on in respect of any further consolidation systems.

[0026] In one example, the system comprises generally horizontally arranged layers of tailings. In one example, the first layer of tailings material and second layer of tailings material and vertically separated from one another by a vertically-impermeable geocomposite drainage layer. In one example, the consolidation system is installed to drain under gravity, for example with the vertically-impermeable drainage layer between the first and second layers of tailings material inclined at a drainage gradient. In one example, the drainage gradient is at least 0.3%, for example up to 10%. Advantageously, even for relatively shallow gradients, the vertically- impermeable geocomposite drainage layer(s) provide an easy route for water to move out of and away from the tailings material.

[0027] In one example, the drainage layer(s) comprise a geocomposite layer.

[0028] In one example, the drainage layer(s) comprise a cuspated core.

[0029] In one example, the drainage layer(s) comprise a single cuspated core. In one example, the drainage layer(s) comprises a geotextile on one or both sides thereof.

[0030] In one example, the drainage layer(s) comprises a double cuspated core. In one example, the drainage layers(s) comprise a geotextile on one, or both sides thereof.

[0031] . In one example, the drainage geocomposite geotextile filter(s) comprises a woven material. In one example, the drainage geocomposite geotextile filter(s) comprises a non-woven material. In one example, the drainage geocomposite geotextile filter(s) comprises a woven / non-woven composite.

[0032] In one example, the geotextile filter comprises a pore size (O90) in the range of 50-600 microns. As will be appreciated, the geotextile filter material choice, pore size and so on is determined with reference to the characteristics of the tailings to be drained in a particular installation.

[0033] In one example, the layer(s) of tailings material comprise reinforcement therein, for example a reinforcement provided by a net, mesh or geocomposite drainage layer.

[0034] In one example, there is a method for consolidation of tailings, the method comprising arranging a vertically-impermeable geocomposite drainage layer between a first layer of tailings material and a second, lower, layer of tailings material.

[0035] In one example, there is provided a tailings consolidation method comprising use of a tailings drainage system comprising a first layer of tailings material above a second layer of tailings material and separated therefrom by a vertically-impermeable drainage layer.

[0036] In one example, the method is performed using a tailings drainage system, and / or containment structure as described herein.

[0037] In one example, the method comprises depositing a layer of tailings material, installing a vertically-impermeable geocomposite drainage layer on the deposited layer of tailings material, and depositing a further layer of tailings material on the vertically-impermeable geocomposite drainage layer.

[0038] In one example, the depositing comprises pumping, and / or mechanically spreading the tailings material.

[0039] In one example, the method comprises constructing a tailings containment structure including a sectional consolidation arrangement. In one example, the method comprises installing a first system for consolidating a first volume of tailings material, and when the tailings material in the first volume of tailings material has reached a consolidation threshold, installinga second system with the first system for consolidating a second volume of tailings material. In one example the method comprises adding a second system alongside such a first system. For example, adding adjacent to, such as horizontally adjacent to, or for example, added so as not to overlie, or only partially overlie such as on, or only on, a side portion thereof.

[0040] In one example, the method comprises providing a water-impermeable drainage layer between the first and second tailing drainage systems.

[0041] In one example, the first and second tailing consolidation system(s), and / or the tailings containment structure are as described herein.

[0042] Although a few example embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.INTRODUCTION!© THE DRAWINGS

[0043] For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example only, to the accompanying diagrammatic drawings in which:Figure 1 shows a schematic side sectional view of a traditional tailings consolidation system;Figure 2 shows a schematic side sectional view of consolidation system according to an example embodiment, with an associated tailings containment structure;Figure 3 shows a schematic side sectional view of a tailings containment structure according to an example embodiment, including first, second and third consolidation systems;Figure 4 shows a vertically-impermeable barrier for use in example embodiments described herein;Figure 5 shows another vertically-impermeable barrier for use in example embodiments described herein; andFigure 6 shows steps in a method for consolidation of tailings according to an example embodiment.DESCRIPTION OF EXAMPLE EMBODIMENTS

[0044] Figure 2 shows a schematic side sectional view of geocomposite tailings consolidation system 200 according to an example embodiment, with an associated tailings containment structure in the form of a dam D. In all the Figures, movement of water is shown schematically by the arrows, both within tailings material and through components of the systems.

[0045] The geocomposite tailings consolidation system 200 comprises a first layer of tailings material 201 above a second layer of tailings material 202 and separated therefrom by a vertically-impermeable drainage layer 205. This arrangement is repeated with third and fourth layers of tailings material 203, 204 and the associated separating layers 205 of vertically- impermeable drainage material. A dam D, with associated outflow O, holds the drainage system 200 within a tailings containment structure.

[0046] The depth of tailings layers Figure 2 has been calculated according to the desired drainage rate of the geocomposite tailings consolidation system 200, and the properties of the tailings to be drained. As will be understood, particle size distribution, water content and permeability of the tailings material are relevant, with smaller particle size tailings and faster drainage require closer vertical spacing. The separation of the overall relatively large depth of tailings material into separate layers, with the capacity in the drainage layers to channel water out of the drainage structure via the outflow improves the rate of drainage and thus consolidation, with various associated benefits as discussed herein. Although the main focus of consolidation in this disclosure is tailings that consist of a fine grained, silty slurry, in practical installations it is to be understood that other mine working waste and residual materials may be included with tailings material. This may be in a proportion of very little of the material to be consolidated, to virtually all said material. For example, the term tailings can, if appropriate, include waste rock, or other heterogenous mine working waste materials.

[0047] Figure 2 shows a vertically-impermeable drainage layer 205' below the lowermost layer of tailings material 204, this layer and a facing layer of vertically-impermeable drainage material 205" on the face of the dam D are in fluid communication with the other drainage layers 205 and the outflow O to carry water out of the containment structure. Separating the tailings in the system from an underlying substrate means makes it easier to manage the outflow from the system overall, for storage, or other downstream distribution as well as preventing unwanted leakage of potentially contaminated leachate. As will be appreciated, arranging the dam D and outflow lower than the tailings material to be drained allows water to leave under the influence of gravity.

[0048] In Figure 4 and 5 respectively, double cuspated 1 , and single cuspated 4 geocomposite materials are shown that are suitable for use as the vertically-impermeable drainage layers. Tailings material is kept out of the drainage voids 2 of the cuspated cores of the material by geotextile filter layers 3, whose properties are chosen to allow ease of access to water, but to keep solid tailings particles out of the layer.

[0049] Figure 3 shows a tailings containment structure that comprises a sectional consolidation arrangement with three geocomposite tailings consolidation systems. A first system 311 , second system 312 and third system 313 are shown. By adding the second and third systems 312, 313 later, next to the side of an earlier-built first system 311 , after sufficient consolidation has been achieved, a safe procedure for draining large amount of tailings materialis possible. As shown in Figure 3, the systems 311 , 312, 313 are separated by vertically- impermeable drainage layers so that water is prevented from moving from the later-built and relatively wet sections to re-wet a previously consolidated lower section. Within each drainage system, at the bottom of the structure and between the tailings and the dam D, vertically- impermeable drainage layers 305, 305', 305" are provided as in Figure 2.

[0050] As shown in Figures 2 and 3, the systems comprise generally horizontally arranged layers. The drainage materials as described herein provide easy fluid flow paths by which water can move out of and away from the tailings material, doing so more quickly than traditional systems and with lower installation overhead due to the more readily transportable nature of the materials. If there are concerns with stability within one or more layers of tailings material, additional geogrid, mesh, net or water-permeable geocomposite material can be provided to give additional reinforcement while the tailings material is relatively wet, or for the longer term after consolidation.

[0051] To show how methods for consolidation of tailings according to example embodiments may be performed, reference is made to Figure 6. In step S601 , a layer of tailings material is deposited. In step S602, a vertically-impermeable drainage layer is installed on layer of tailings material that was previously deposited in step S601 . In step S603 the method comprises depositing a further layer of tailings material on the vertically-impermeable drainage layer that was installed in step S602. According to the composition of the tailings material, the depositing thereof is performed by pumping, and / or mechanically spreading the tailings material.

[0052] In another method for tailings consolidation, step S604 maybe performed. At step S604, a tailings containment structure with sectional consolidation arrangement is made. That is, after steps S601 to S603, tailings consolidation takes place over time, to a point where a consolidation threshold is reached. Thereafter, at step S604, a steps S601 to S603 are repeated, with the layers deposited and installed adjacent the consolidated tailings in the earlier- built layers and separated therefrom by a water-impermeable barrier. In this way, the area for consolidation can be used effectively as described above.

Claims

CLAIMS1. A tailings consolidation system (200), the system comprising a vertically-impermeable geocomposite drainage layer (205) between a first layer of tailings material (201) and a second, lower, layer of tailings material (202), in which the vertically-impermeable drainage layer (205) comprises a geocomposite layer formed with a single or double cuspated core, with a geotextile filter (3) on one or both sides side thereof, the vertically-impermeable drainage layer (205) arranged to stop water moving down from the first layer of tailings material (201) to the second layer of tailings material (202) and arranged to stop capillary movement of water up from the second layer of tailings material (202) and into the first layer of tailings material (201) above, and providing an in-plane flow capacity for water to move through the system to an outflow across both sides thereof.

2. The system (200) of claim 1 , wherein the geotextile filter (3) comprises a filter with pore size (O90) in the range of 50-600 microns.

3. The system (200) of any preceding claim, associated with a tailings containment structure that includes a vertically-impermeable geocomposite drainage layer (205') for use below the lowermost layer of tailings to separate tailings from an underlying substrate.

4. The system (200) of any preceding claim, associated with a tailings containment structure that includes a dam.

5. The system (200) of any preceding claim, associated with a tailings containment structure that includes an outflow, with a fluid flow path from the vertically-impermeable drainage layer (205) to the outflow such that in use water passing from the tailings into the drainage layer (205) flows from the tailings containment structure at the outflow.

6. The system (200) of any preceding claim comprising a reinforcement net, mesh or water- permeable geocomposite layer for in use reinforcing the first and / or second layer of tailings material (201 , 202).

7. A method for consolidation of tailings, comprising arranging a vertically-impermeable geocomposite drainage layer between a first layer of tailings material and a second, lower, layer of tailings material to produce the system of any one of claims 1 to 6.

8. The method of claim 7, comprising depositing (S601) a layer of tailings material, installing (S02) a vertically-impermeable geocomposite drainage layer on the deposited layer of tailings material, and depositing (S603) a further layer of tailings material on the vertically- impermeable drainage layer, said depositing (S601 , S603) performed by pumping, and / or mechanically spreading the tailings material.

9. The method of claim 7 or 8, comprising constructing (S604) a tailings containment structure with sectional consolidation arrangement, in which a first system for consolidating a first volume of tailings material is installed, and when tailings material in the first volume of tailings material has reached a consolidation threshold, installing a second system on the first system for consolidating a second volume of tailings material.

10. The method of claim 9, wherein the second system is installed alongside the first system.

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