Mining method using a disk cutter

Abstract

A method of mining rock using a disk cutter comprising a cutter body having a diameter d and a thickness t, a plurality of tool holders mounted on the peripheral surface of the cutter body, and a plurality of cutting elements attached to the tool holders, comprising: cutting a first slot in the rock at a first cutting position of the disk cutter; moving the disk cutter to a second cutting position to the left or right of the first cutting position; cutting a second slot in the rock such that the second slot is spaced from the first slot by a distance S, wherein at least one of the first slot and the second slot has a slot depth D, and the ratio of the slot depth D to the distance S is in the range of 2 to 16; A method is provided that includes the above steps.

Description

Technical Field

[0001] The present disclosure relates to a method of mining materials using a disk cutter. In particular, the present invention relates to a method of mining rock using a disk cutter comprising a polycrystalline diamond cutter. More particularly, the present invention relates to a method of mining cuboid blocks from materials such as kimberlite and granite.

Background Art

[0002] British Patent Application Publication No. 2589736 discloses a disk cutter 10 comprising a cutter body 14, a plurality of tool holders 16, and a plurality of cutting elements 18 mounted on the tool holders 16, as shown in FIGS. 1 and 2. The cutting elements 18 are arranged within the tool holders 16 according to an arrangement that reduces the cutting force during use. In a particular embodiment, six or more disk cutters 10 regularly spaced from each other are arranged on a common drive spindle. The spacing of the disk cutters 10 is selected according to the cutting depth required in the target rock layer and the mechanical properties of the rock.

[0003] The problem with this configuration is that it is difficult to achieve complete cutting synchronization of the various disk cutters when they engage with the rock. No part of the rock has exactly the same mechanical properties as the part of the rock adjacent to it, and thus, some disk cutters cut relatively easily, while other disk cutters experience greater resistance. As a result, this causes problems for the cutting assembly being managed, leading to stoppages and mechanical failures. It can also result in non-uniform slot depths.

[0004] The object of the present invention is to address the above problems.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] According to a first aspect of the present invention, there is provided a method for mining rock using a disk cutter comprising a cutter body having a diameter d and a thickness t, a plurality of tool holders mounted on the circumferential surface of the cutter body, and a plurality of cutting elements attached to the tool holders, for example, mounted within the tool holders, the method comprising: cutting a first slot in the rock at a first cutting position of the disk cutter; moving the disk cutter to a second cutting position, for example, to the left or right of the first cutting position; cutting a second slot in the rock such that the second slot is spaced from the first slot by a distance S, wherein at least one of the first slot and the second slot has a slot depth D, and the ratio of the slot depth D to the distance S is in the range of 2 to 16; A method is provided that includes the above steps.

[0007] According to a second aspect of the present invention, there is provided a method for mining rock using a disk cutter comprising a cutter body having a diameter d, a plurality of tool holders mounted on the circumferential surface of the cutter body, and a plurality of cutting elements attached to the tool holders, for example, mounted within the tool holders, the method comprising cutting a slot depth D in the rock at a cutting position of the disk cutter, wherein the ratio of the slot depth D to the diameter d of the cutter body is from about 0.15 to about 0.50.

[0008] Optionally, the ratio of the slot depth D to the diameter d of the cutter body is from about 0.15, about 0.20, about 0.25, about 0.30 or about 0.35 to about 0.49, about 0.48, about 0.47, about 0.46, about 0.45 or about 0.40.

[0009] Optionally, the ratio of the slot depth D to the diameter d of the cutter body is from about 0.15 to about 0.50, or from about 0.15 to about 0.49, or from about 0.15 to about 0.48, or from about 0.15 to about 0.47, or from about 0.15 to about 0.46, or from about 0.20 to about 0.45, or from about 0.25 to about 0.40, or from about 0.30 to about 0.40, or from about 0.35 to about 0.40, or from about 0.32 to about 0.37, or from about 0.34 to about 0.37, or from about 0.34 to about 0.36.

[0010] Further preferred features and / or optional features of the first and second aspects of the present invention are presented in the dependent claims.

[0011] Next, an improved mining method will be described by way of example with reference to the accompanying drawings.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

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Figure 5

Figure 6

Figure 7

Figure 8a

Figure 8b

Figure 8c

Figure 9

Figure 10

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Figure 12

Figure 13

DETAILED DESCRIPTION OF THE INVENTION

[0013] As shown in FIGS. 1 and 2, the disk cutter 10 is used to cut the rock 12. The disk cutter 10 includes a cutter body 14 having a diameter d and a thickness t, a plurality of tool holders 16 mounted on the peripheral surface of the cutter body 14, and a plurality of cutting elements 18 mounted on the tool holders 16. The cutting elements 18 are arranged in order within each set of repetitions of the tool holders 16. The cutting elements 18 include polycrystalline diamond.

[0014] During use, the disk cutter 10 rotates at high speed and is sent towards the rock 12. When the disk cutter advances and engages with the rock 12, cutting begins and the first slot 20 is gradually formed in the rock 12 (see Figure 3). When the target slot depth D is obtained, the disk cutter 10 is withdrawn from the slot. The disk cutter 10 is moved to a second cutting position and the cutting operation is repeated to form the second slot 22. The second slot 22 may be to the left or right of the first slot 20 on the rock face, or above or below the first slot 20. The second slot 22 is spaced from the first slot 20 by a distance S. The distance S is equal to the spacing between the slots 20, 22. To minimize the energy required for subsequent rock fragmentation, the ratio of the slot depth D to the distance S must be in the range of 2 to 16. This range was determined based on the computer simulation work described later. The distance S and the slot depth D are optimized based on the properties of the rock 12, indirectly taking into account the design of the cutter body 12.

[0015] The diameter of the cutter body 14 is in the range of about 1.0 to about 5.0 m, for example about 1.0 m to about 4.0 m, for example about 1.0 m to about 3.0 m, for example about 1.0 to about 2.0 m, for example about 1.0 m to about 1.8 m, for example 1.0 to 1.8 m. In one embodiment, the diameter of the cutter body 14 is 1.0 m. In another embodiment, the diameter of the cutter body 14 is 1.5 m. In a further embodiment, the diameter of the cutter body 14 is 1.75 m.

[0016] The first and / or second slot has a width W that is smaller than the thickness t of the cutter body 14. The slots 20, 22 have widths in the range of 20 to 80 mm. In practice, for rock materials having an unconfined compressive strength exceeding 200 MPa, a slot width of 20 mm is recommended. Similarly, for rock materials having an unconfined compressive strength in the range of 150 to 200 MPa, a slot width of 40 mm is recommended. For rock materials having an unconfined compressive strength in the range of 60 to 150 MPa, a slot width of 60 mm is recommended. For rock materials having an unconfined compressive strength in the range of 30 to 60 MPa, a slot width of 80 mm is recommended. An alternative term for unconfined compressive strength is uniaxial compressive strength.

[0017] Computer simulation using finite element analysis According to the International Society for Rock Mechanics and Rock Engineering (ISRM), the strength of rocks can be described as medium strength, high strength, and very high strength, as shown in Table 1. More quantitatively, the uniaxial compressive strength, i.e., UCS, is the most widely cited parameter for representing the properties of rocks and is an important factor to be considered in the design for rock cutting. In short, a tougher rock requires a greater force to be applied until it is crushed. Examples of medium-strength rocks include concrete and sandstone. An example of a high-strength rock is kimberlite. An example of a very high-strength rock is granite. In the present disclosure, concrete and granite, which represent both extremes, are particularly considered.

Table 1

[0018] In the study, the slot depth D and the distance (also referred to as "spacing") S were investigated. The selection of D and S directly affects the load required when the rock 12 is crushed from the base 24 of the slot near the floor of the slot. The loading condition was to apply a horizontal force to the upper edge of the slot, indicated as a whole by the reference numeral 26. The output variable was the maximum principal stress. It should also be noted that for the purposes of this study, the rock damage initiation criteria are defined as when the maximum principal stress reaches the uniaxial compressive strength.

[0019] The simulation results for concrete and granite are shown in Tables 2 and 3 respectively. The same results are also shown in Figures 4 and 5.

Table 2

Table 3

[0020] Similar simulations were also performed for kimberlite having a uniaxial compressive strength of 50 - 100 MPa, but the results are not shown herein.

[0021] When the ratio of the depth D to the distance S is less than 2, the load required to crush the rock using the crushing tool 28 becomes impractically high, and increasingly high energy consumption is required to drive the disk cutter 10 to generate the kerf. Using the currently available sizes of the disk cutters referred to herein, a ratio exceeding 15 cannot be achieved.

[0022] The crushing tool 28 may adopt one of several different forms. The tool 28 may be a wedge-shaped tool as shown in FIG. 3. As the wedge-shaped tool is gradually inserted into the slots 20, 22, a bending force is generated at the bases of the slots 20, 22, and finally cracks occur in the rock 12. Alternatively, the crushing tool 28 may be configured to generate depressions in the rock. Other configurations of the crushing tool will be described in more detail below. It should be noted that the crushing tool 28 is completely optional and not essential to the present invention. If the ratio of the depth D to the distance S becomes too large, the rock is more likely to be crushed by its own load and vibration. Therefore, the crushing tool 28 is not required in all situations. However, if the rock is crushed in another way, it tends to be crushed in an uncontrolled manner, resulting in more waste, so it is preferably used.

[0023] Generally, the greater the slot depth D, the higher the cutting efficiency. However, as the slot depth D increases, the torque and vibration of the cutter body also increase, increasing the risk of inefficient excavation. Therefore, there is a balance between the slot depth D and the diameter d of the cutter body 20, which can be characterized by the ratio of the slot depth D to the diameter d of the cutter body 20. For efficient cutting, this parameter is ideally at least 0.15, 0.20, 0.25, 0.30 or 0.35, and / or less than 0.50, 0.49, 0.48, 0.47, 0.46, 0.45 or 0.40. For example, the ratio of the slot depth D to the diameter d of the cutter body 20 can be about 0.15 to about 0.50, or about 0.15 to about 0.49, or about 0.15 to about 0.48, or about 0.15 to about 0.47, or about 0.15 to about 0.46, or about 0.20 to about 0.45, or about 0.25 to about 0.40, or about 0.30 to about 0.40, or about 0.35 to about 0.40, or about 0.32 to about 0.37, or about 0.34 to about 0.37, or about 0.34 to about 0.36.

[0024] The slot depth D of 340 mm can actually be achieved using a cutter body 14 having a diameter of 1.0 m. Thereby, the ratio of the slot depth D to the diameter d of the cutter body becomes 0.34. The slot depth D of 540 mm can actually be achieved using a cutter body 14 having a diameter of 1.5 m. Thereby, the ratio of the slot depth D to the diameter d of the cutter body becomes 0.36. The slot depth D of 740 mm can actually be achieved using a cutter body 14 having a diameter of 1.75 m (giving a ratio of the slot depth D to the diameter d of the cutter body of 0.42), but a slot depth D of 640 mm (giving a ratio of the slot depth D to the diameter d of the cutter body of 0.37) was considered preferable during initial field tests using a diameter of the same size.

[0025] Damage at the base 24 of the slot (i.e., the position furthest from the opening to the slot) can be due to tensile stress, and since the ratio of the uniaxial compressive strength to the tensile stress is about 10, the actual force (load, kN) required can be up to 10 times smaller.

[0026] In actual mining applications, locations where damage may occur include the following situations. · When the stress at the load contact point exceeds the uniaxial compressive strength of the rock material, · When the tensile stress exceeds the maximum tensile strength (usually at the bottom of the slot), and · When microcracks are present.

[0027] Therefore, the principle for slot size selection is that the stress at the load contact point must not exceed the uniaxial compressive strength of the rock material; otherwise, the rock will be crushed at the load point.

[0028] The stress at the load contact point depends on the shape and contact area of the crushing tool 28 (e.g., wedge tool), as well as load conditions such as the angle of incidence and whether they are dynamic. As part of the study, the height of the load contact points within slots 20, 22 was also examined. This was an attempt to identify the optimal position for applying the crushing tool 28 after the slots were formed.

[0029] The following was found. · The load at the upper position may generate the maximum bending stress at the bottom / base of the slot. · As the height decreases, the bending stress decreases linearly.

[0030] Figure 6 shows that the loads at various positions on the rock require various loads to break the rock. The "slot height" is measured from the opening of the slot, away from the edge, towards the floor of the slot. The results show that the closer to the edge of the rock 12 (near the arrow 26), the smaller the required load. However, in practice, the best position is not necessarily at the top of slots 20, 22 because the impact of the crushing tool 28 may cause damage to the rock 12 at that point. The optimal contact position may actually be at a lower position, that is, a deeper position within the slot. Preferably, the crushing tool 28 contacts the rock at a position that is at least 15% of the entry path into the slot. If the position is less than 15% of the entry path into slots 20, 22, the rock strength at the edge will decrease dramatically due to the unrestricted actual conditions, resulting in a higher likelihood of undesirable damage.

[0031] This study also included examining the loads required to break the rock at various angles of incidence. Specifically, the relationship between the bending stress at the bottom of the slot and the variable load angle was investigated. The results are shown in Figure 7, where a "collision angle" of 0 (zero) represents the condition where the load of the crushing tool 28 is applied horizontally.

[0032] The following was found. · The horizontal load produces the maximum bending stress. As the angle increases, as shown in Figure 7, the bending stress at the bottom decreases accordingly.

[0033] The last aspect of the study was to investigate how the depressions affect the initiation and propagation of cracks (see Figures 8a, 8b, and 8c). Using a hammer, which is a type of crushing tool 28, one or more depressions 30 were formed in the rock. Based on the simulations, the following was found. · Cracks tend to propagate along the direction of the depressions. · The spacing between the depressions and the depth of the depressions significantly affect the crack propagation between the depressions.

[0034] Therefore, it is preferable that facing depressions 30 are formed in each of the first and second slots 20, 22. In this aspect, by controlling the spacing between the pair of first and second slots 20, 22, cracks can be predictably initiated and promoted to extend between the depressions 30. They also reduce the crushing force required. The depression 30 or each depression can be formed to a depth of up to 95% of the distance S, or up to 90% of the distance S, or up to 85% of the distance S, or up to 80% of the distance S, or up to 75% of the distance S, or up to 70% of the distance S, or up to 65% of the distance S, or up to 60% of the distance S, or up to 55% of the distance S, or up to 50% of the distance S, or up to 45% of the distance S, or up to 40% of the distance S, or up to 35% of the distance S, or up to 30% of the distance S, or up to 25% of the distance S, or up to 20% of the distance S, or up to 15% of the distance S, or up to 10% of the distance S, or up to 5% of the distance S. Preferably, the depression 30 or each depression is formed to a depth of 20% of the distance S. These factors help to facilitate the recovery of the rock above the crack propagation line in a substantially rectangular block.

[0035] The expression "facing each other" is intended to mean that the cross-section of the depression decreases in the direction in which the depression faces. For example, if the depression is conical, the direction indicated by the apex is the direction in which the depression faces. The hemispherical depression shown in Figure 8a faces the right side of the paper.

[0036] Preferably, the depression 30 or each depression is formed in or near the floor of the slots 20, 22.

[0037] As described above, the crushing tool 28 may be configured in several other ways.

[0038] In the examples shown in FIGS. 9 and 10, the crushing tools 28, 300 include an elongated tool body 302 having a longitudinal axis and a tool head 304 at one end of the tool body 302. The tool head 304 includes one or more protrusions 306 extending from its surface. To facilitate crushing, the crushing tools 28, 300 are at least partially inserted into the slots 20, 22. The crushing tools 28, 300 rotate slowly about the longitudinal axis from the insertion direction to the crushing direction. In this manner, the tool head 304, and more specifically the protrusions 306, thereby impact at least one columnar portion of an adjacent rock 12. This impact may be sufficient to cause a crack in the rock 12, which facilitates the subsequent recovery of the fractured rock layer. The crushing of the rock by this slow rotation advantageously uses minimal energy to crush the rock at the base of the slots 20, 22. Optionally, the tool head 304 is configured to impact two adjacent columnar portions of the rock 12.

[0039] In the examples shown in FIGS. 11 and 12, the crushing tools 28, 400 include a tool head 402, which includes an elongated disk carrier 404, a base mount 406, and one or more mini disk cutters 408 supported by the disk carrier 404. The disk carrier 404, and thus the mini disk cutters 408 as well, are movable relative to the base mount 406. Preferably, the tool head 402 includes three or more mini disk cutters 408 spaced apart from each other along the disk mount 406. The mini disk cutters 408 preferably include a carbide material. Unlike the main disk cutter 10, the mini disk cutters 408 have a circular base and a compressed pyramid shape with a low height.

[0040] Each mini disk cutter 408 may extend in a plane orthogonal to the longitudinal section of the disk mount 406. Alternatively, each mini disk cutter 408 may extend in a plane forming an angle with respect to the longitudinal section of the disk mount 406, and the crushing tools 28, 400 are configured such that the angle is adjustable. When at least partially inserted into the slots 20, 22, the crushing tools 28, 400 are operable to cut into the columnar portion of the rock using the mini disk cutters 408 of the tool head 402. In this manner, cracks in the rock 12 can be initiated at multiple locations, thereby facilitating the subsequent recovery of the crushed rock layer. This particular approach to rock crushing advantageously uses minimal energy to crush the rock along a predetermined direction.

[0041] In the example shown in FIG. 13, the crushing tool 28 has a tool head 500 comprising one or more striking elements 502 operable to extend outwardly or retract inwardly, for example using a hydraulic expander. The striking element 502 may comprise a cemented carbide striking tip 504. In use, the striking element 502 is launched, i.e., rapidly deployed, from the tool head 500 towards the adjacent rock 12. Thereby, the impact from the striking tip 504, which can cause the above-described depression in the rock 12, and thus the impact into the depression, may be sufficient to initiate cracking and subsequent propagation. Again, this facilitates the subsequent recovery of the crushed rock layer. Optionally, two oppositely directed striking elements 502 are fired towards the columnar portions of the rock 12 on both sides of the slots 20, 22.

[0042] Optionally, as seen in FIG. 13, multiple tool heads can be deployed and operated at multiple depth positions within the slots 20, 22 to forcibly crush the rock 12.

[0043] In summary, the inventors have developed an improved mining method that minimizes the energy required to crush rock, particularly in the mining of hard rock.

[0044] Although the present invention has been particularly shown and described with reference to embodiments, it will be understood by those skilled in the art that various changes in form and detail can be made without departing from the scope of the present invention as defined by the appended claims.

Claims

1. A method for mining rock using a disk cutter comprising a cutter body having a diameter d and a thickness t, a plurality of tool holders mounted on the circumferential surface of the cutter body, and a plurality of cutting elements attached to the tool holders, comprising: cutting a first slot in the rock at a first cutting position of the disk cutter; moving the disk cutter to a second cutting position; cutting a second slot in the rock such that the second slot is spaced from the first slot by a distance S, wherein at least one of the first slot and the second slot has a slot depth D, and the ratio of the slot depth D to the distance S is in the range of 2 to 16; A method comprising.

2. The method according to claim 1, wherein the second cutting position is to the left or right of the first cutting position.

3. The method according to claim 1, wherein the second cutting position is above or below the first cutting position.

4. The method according to any one of claims 1 to 3, wherein the slot depth D is in the range of 300 to 800 mm.

5. The method according to claim 4, wherein the slot depth D is in the range of 300 to 400 mm.

6. The method according to claim 4, wherein the slot depth D is in the range of 500 to 600 mm.

7. The method according to claim 4, wherein the slot depth D is in the range of 700 to 800 mm.

8. The method according to any one of claims 1 to 7, wherein the diameter d of the cutter body is in the range of 1.0 to 5.0 m.

9. The method according to claim 8, wherein the diameter d of the cutter body is 1.0 m.

10. The method according to claim 8, wherein the diameter d of the cutter body is 1.5 m.

11. The method according to claim 8, wherein the diameter d of the cutter body is 1.75 m.

12. The method according to any one of claims 1 to 11, wherein the distance S is in the range of 50 to 200 mm.

13. The method according to any one of claims 1 to 12, wherein the rock has a uniaxial compressive strength of 25 to 50 MPa.

14. The method according to any one of claims 1 to 12, wherein the rock has a uniaxial compressive strength of 50 to 100 MPa.

15. The method according to any one of claims 1 to 12, wherein the rock has a uniaxial compressive strength of 100 to 250 MPa.

16. The method according to any one of claims 1 to 15, wherein the first slot and / or the second slot has a width W, and the width is in the range of 20 to 80 mm.

17. The method according to claim 16, wherein the slot width is 20 to 40 mm, and the unconfined compressive strength of the rock is 200 MPa or more.

18. The method according to claim 16, wherein the slot width is 40 to 60 mm, and the unconfined compressive strength of the rock is in the range of 150 to 200 MPa.

19. The method according to claim 16, wherein the slot width is 60 to 80 mm, and the unconfined compressive strength of the rock is in the range of 60 to 150 MPa.

20. The method according to claim 16, wherein the slot width is 60 to 80 mm, and the unconfined compressive strength of the rock is in the range of 30 to 60 MPa.

21. The method according to any one of claims 1 to 20, further comprising the step of at least partially inserting a rock-breaking tool into the first slot and the second slot.

22. The method according to any one of claims 1 to 21, further comprising the step of forming a depression in the rock adjacent to the first slot and / or the second slot.

23. The method according to claim 22, wherein the depression is formed to a depth of at most 20% of the distance S.

24. The method according to claim 22 or 23, wherein the depression is formed at a position in the slot or in each slot, the position is measured from the opening of the slot, and corresponds to at least 15% of the slot depth.

25. The method according to claim 24, wherein the depression or each depression is formed on or near the bottom of the slot.

26. The method according to any one of claims 22 to 25, comprising the step of forming a depression in the adjacent rock of the first slot and the second slot, and the depressions face each other.

27. A method of mining rock using a disk cutter comprising a cutter body having a diameter d, a plurality of tool holders attached to the circumferential surface of the cutter body, and a plurality of cutting elements attached to the tool holders, the method comprising the step of cutting a slot depth D in the rock at the cutting position of the disk cutter, and the ratio of the slot depth D to the diameter d of the cutter body is about 0.15 to about 0.

50.

28. The method according to claim 27, wherein the ratio of the slot depth D to the diameter d of the cutter body is from about 0.35 to about 0.40.

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