MINING METHOD

Abstract

A method of mining comprising the steps of introducing a mining head into a borehole fracturing the ore with the mining head and extracting the fractured ore through a borehole to a location remote from the mining head.

Claims

1. A method of mining comprising the steps of: introducing a mining head into a borehole; fracturing the ore with the mining head; and extracting the fractured ore through a borehole to a location remote from the mining head; wherein the steps of fracturing the ore and extracting the fractured ore to a location remote from the mining head are controlled remote from the mining head and wherein the step of fracturing the ore, radially expands the borehole.

2. A method of mining in accordance with claim 1, wherein the steps of: fracturing the ore with the mining head; and extracting the fractured ore through a borehole to a location remote from the mining head; are conducted simultaneously.

3. A method of mining in accordance with claim 1 or claim 2, wherein the borehole containing the mining head is the mining borehole and the borehole through which fractured ore is extracted is the extraction borehole and the mining borehole and the extraction borehole are the same borehole or different boreholes.

4. A method of mining in accordance with any one of the preceding claims, wherein the ore is fractured by mechanical ablation, laser spalling, flame or heat spalling, plasma spalling, water jet ablation, electrical ablation, sonic ablation, freezing ablation, chemical dissolution or leaching or combinations thereof.

5. A method of mining in accordance with any one of the preceding claims, wherein the fractured ore is extracted in an extraction duct.

6. A method of mining in accordance with any one of the preceding claims, wherein the method comprises the further step of: cooling the mine face either simultaneously with the step of fracturing the ore or subsequent to the step of fracturing the ore.

7. A method of mining in accordance with any one of the preceding claims, wherein the mining head comprises a laser mining head.

8. A method of mining in accordance with claim 7, wherein the laser mining head is in communication with a laser source located remotely from the laser mining head.

9. A method of mining in accordance with any one of the preceding claims, wherein the method comprises the further step of: generating and delivering a laser beam to a mine face.

10. A method of mining in accordance with claim 9, wherein the laser beam is continuous or pulsed.

11. A method of mining in accordance with any one of the preceding claims, wherein the step of extracting the fractured ore is conducted by air vacuum suction, venturi, water injection and slurry pumping, mud injection and density floatation, mechanical means or combinations thereof.

12. A method of mining in accordance with any one of the preceding claims, wherein the method comprises the further step of: determining the location of the ore.

13. A method of mining in accordance with any one of the preceding claims, wherein the mining head is provided with means to monitor and record operations.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0099] Further features of the present invention are more fully described in the following description of several non-limiting embodiments thereof. This description is included solely for the purposes of exemplifying the present invention. It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above. The description will be made with reference to the accompanying drawings in which:

[0100] FIG. 1 is a cross section of a borehole comprising equipment for use in accordance with an embodiment of the present invention;

[0101] FIG. 2 is a schematic of a laser beam expander for use in accordance with an embodiment of the present invention;

[0102] FIG. 3 is a schematic of a laser snake for use in accordance with an embodiment of the present invention;

[0103] FIG. 4 is a schematic series of drawings depicting the use of an embodiment of the present invention;

[0104] FIG. 5 is a schematic drawing depicting the use of an embodiment of the present invention;

[0105] FIG. 6 is a schematic series of drawings depicting the use of an embodiment of the present invention;

[0106] FIG. 7 is a schematic representation of a mining plan schedule;

[0107] FIG. 8 is a schematic drawing depicting the use of an embodiment of the present invention; and

[0108] FIG. 9 is a schematic drawing depicting the use of an embodiment of the present invention;

DESCRIPTION OF EMBODIMENTS

[0109] Throughout this specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0110] This invention is a new mining method for extraction of ore wherein it is a “non-entry method” for rock mining. The ore is broken in situ by remotely accessing it through a borehole. The broken ore is then recovered from the borehole using vacuum, venturi, pumping or mechanical methods and processed to remove minerals of value. No personnel are required to be at the mine face in the mining process. This invention is unique in its utilization of boreholes only, to intersect, define, access and extract rock ore bodies.

[0111] Breaking of the ore in situ is achieved by a number of methods that may include mechanical ablation, laser spalling, flame or heat spalling, plasma spalling, water jet ablation, electrical ablation, sonic ablation, freezing ablation, chemical dissolution or leaching. Breaking can be achieved by utilising one of these methods or a combination of a number of them.

[0112] In summary, a borehole is drilled into the mineralized zone (i.e. ore). A specialised mining head is lowered down the borehole to the desired position within the ore. The head is activated and it fractures the ore into particles that are then transported to the surface via this same borehole that the mining head is occupying, or an adjacent borehole.

[0113] Traditional blasting methods of mining can provide fragmented ore the size of cobbles to very large boulders which require further crushing prior to grinding. Crushing cobbles and boulders is very energy and cost intensive. By contrast, the method of the present invention provides fragmented ore the size of fine to medium gravel. More specifically, the fragmented ore chips are about 1-20 mm in diameter. Advantageously, fragments of this size may not require crushing.

[0114] The ore is progressively broken and recovered in a planned sequence. Numerous mining heads may be deployed in boreholes in the same ore zone simultaneously. Numerous ore zones or areas may also be worked simultaneously.

[0115] In FIG. 1 there is shown a cross section of a borehole 10 containing a mining head in accordance with the present invention. The borehole 10 contains a downhole service duct 12 and an extraction duct 14. The downhole services duct 12 contains an energy duct (i.e. laser) 16 and services ducts such as electrical 18, air 20, water 22, camera 24 and data 26.

[0116] In a borehole of about 200 mm diameter, the extraction duct is about 100 mm.

[0117] The mining head as such is provided with an energy supply (such as electricity, hydrocarbon, fibre optic), a power supply, an air supply, a water supply, a communications cable or a combination of these and is remotely controlled from outside the excavation void and borehole.

[0118] The mining head is capable of three dimensional movement. It can move up and down and across the mine face, or it can rotate.

[0119] In FIG. 2 (a), there is shown a schematic laser beam expander 30 appropriate for use in the present invention. The laser beam expander 30 comprises a laser fibre 32, a fibre connector 34, a diamond-turned zinc sulfide collimating lens 36, a rotation collar 38, an angling mirror 40, a cover slide 42 and an exiting laser beam 44. Alternatively, FIG. 2 (b) shows a schematic laser beam expander incorporating an output focusing lens 46.

[0120] In FIG. 3, there is shown a schematic laser snake 50 such as that available from OC Robotics (http://www.ocrobotics.com/lasersnake2/) appropriate for use in the present invention. The laser snake 50 comprises outlets for light 52, compressed air nozzle 54, camera 56 and laser beam output 58. The laser snake 50 is flexible and may be used to facilitate the movement of a laser mining head across the mine face and maintain a desired and substantially constant stand-off distance from the mine face.

[0121] In use, the laser mining head is preferably maintained about 30 cm from the mine face. As the mine face of the ore body moves with the spalling, the laser mining head may be moved to maintain the stand-off at the desired distance.

[0122] It will be appreciated that the distance between adjacent boreholes will be influenced by the method of fracturing. For example, laser fracturing may be conducted to a distance of about 3 m from the center of a borehole. In such a circumstance, adjacent boreholes may be placed approximately 6 m apart.

[0123] In FIG. 4, there is shown a schematic series of drawings depicting the use of the method of the present invention. In FIG. 4a, there is provided a borehole 60 in the surface 62 of the earth. The laser mining head 64 and ancillary equipment are lowered into the borehole to the desired depth. In FIG. 4b the laser beam is operated and the ore body in situ fractured. The remaining cavity may be circular in cross-section, oval shaped or irregular. The fragmented ore is not depicted in FIG. 4b, although it will be recognised that the mine face 66 has retreated. As the laser continues operation, the mine face 66 continues to retreat as shown in FIG. 4c. Mining is ceased at this depth either when the edges of the ore body have been reached or maximum depth permissible by the laser beam has been reached. The laser head 64 is then raised and the process repeated as shown in FIG. 4d and FIG. 4e until the ore body is removed. If the ore body does not reach the surface, it is not necessary for the mining operation to continue to the surface. In that way, unwanted barren material is not mined.

[0124] As the mining head rises, the extraction tube remains at or near the bottom of the mined cavity. As the mining head rises, fragmented ore falls to the bottom of the cavity and can be extracted. The ore fragments are removed by venturi method or a vacuum. The depth of the borehole may have an influence on the method of choice.

[0125] In FIG. 5, there is shown a schematic drawing depicting the use of the method of the present invention. In FIG. 5, there is provided a borehole 60 in the surface 62 of the earth. The laser mining head 64 and ancillary equipment are lowered into the borehole to the desired depth. A suction unit 70 and a coil rig 72 are provided at the surface 62. The mining head 64 is in communication with the coil rig 72 which controls the position of the mining head 64. An extraction tube 74 is in communication with the suction unit 70. The extraction tube 74 extracts fragmented ore (no shown) from the bottom of the borehole 60.

[0126] In FIG. 6, there is shown a number of schematic drawings of a mine face outlining the movement sequence 80 of a laser beam across it. It will be appreciated that the movement of the laser head may take many forms, depending on the size and shape of the ore body and the optimum in situ fracturing sequence. In FIGS. 6(a), 6(b) and 6(c), the movement sequence is a result of continuous laser application. In FIG. 6(d), the movement sequence is a result of a pulsed laser application.

[0127] In FIG. 7, there is provided a schematic representation of a mining plan schedule in accordance with the present invention. In a sequence of five bore holes, there is provided a first borehole 90, a second borehole 92, a third borehole 94, a fourth borehole 96 and a fifth borehole 98. The boreholes are about 6 m apart from each other. The first borehole 90 is mined and the ore extracted first up to the desired depth and configuration. This is followed by the third borehole 94, the second borehole 92, the fifth borehole 98 and finally the fourth borehole 96. There may also be provided a sequence of backfilling or partial backfilling of the mined cavities in the same order such that adjacent cavities are back-filled prior to commencing mining in a borehole. Advantageously, it is not necessary to mine all of the five boreholes before extracting the fragmented ore. Other ore extraction sequences may be used to optimize the ore recovery and backfilling sequence.

[0128] It is possible in accordance with present invention to target narrow ore veins and mine them irrespective of the shape or inclination of the vein. In FIG. 8, there is provided a schematic of a narrow vein 100 and a borehole. The borehole has an initial vertical portion 102 and a subsequent inclined portion 104 running through the vein 100. A mining head (not shown) can be placed into the borehole down to the bottom of the inclined portion 74 and the vein mined as described above.

[0129] In FIG. 9, there is provided a schematic of a mining operation in accordance with an embodiment of in the present invention in an existing underground mine. The underground mine comprises an access ramp 110 and a series of level drives 112 to access the ore body 100. In this embodiment, a second ore body 114 sits remote from the major ore body 100. For a variety of factors, it may not be economic to mine the second ore body 114 using conventional underground mining techniques. Under these circumstances, the suction unit 70 and a coil rig 72 will be located in the underground mine and a borehole drilled into the second ore body 114 and the ore fractured and extracted as described above.

[0130] When undertaking a mining operation, the location of an ore body will generally be known with a high degree of accuracy. This information can be relied upon to predict the extent of ore bodies in order to minimize the amount of barren material that is extracted. Additionally and alternatively, it is possible with the present invention to monitor the content of an ore body during the mining operation. This may entail the use of in stream or mine face spectral analysis technology that may be located on the mining head to analyse the mine face surface or ore fragments as they are created. In one form of the invention, this may entail the use of infrared scanning.

[0131] It will be appreciated that the method of the present invention, may be more applicable to some ore types than others. Ores that exists in crystalline veins or lenses such as gold, silver, copper, nickel and lithium ores will be most suited to mining by the present invention.

[0132] The present invention provides the following advantages: [0133] optimisation of ore recovery; [0134] less dilution from the surrounding rock; [0135] reduction in capital expenditure on mine development; [0136] no personnel are required to enter the mining area or void leading to a significant increase in the safety of personnel in the mining operation; [0137] a small area of surface disturbance required for the mining operation lowering the environmental impact of the works; and [0138] all access and broken ore retrieval is undertaken through a borehole;

[0139] Laboratory trials were conducted on samples of granite, sandstone, basalt and quartz (200×200×200 mm). The laboratory was fully equipped with a fibre laser unit, robotic laser mount and control unit, fume extraction and other instrumentation generally as below: [0140] LDF 16000—60. Variable output 2 to 16 kW; [0141] FOC—600 μm; [0142] Lens Arrangement 1—OTS-5 optic arrangement with collimating (50 mm) and focusing lens, circular spot. Side mount camera; [0143] Lens Arrangement 2—OTZ-5 optic arrangement with collimating and focusing lens, square spot; [0144] Lens Arrangement 3—OTS-4 optic arrangement with collimating lens (32 mm), circular spot; [0145] Laser Mount—Kuka RL80 multi axis, digitally controlled robot mount (ROB01) and fixed worktable; [0146] Vacuum fume extraction system; and [0147] Compressed air lance (nominal 100 psi) focused upon the exposure area moving in lock step with the laser.

[0148] The results of the trials are presented in Tables 1 to 7.

[0149] Various traverse tests were undertaken in continuous and pulsed power modes. It was determined that slower speeds and higher powers provided the most aggressive conditions for removal of material, but care was required to avoid melting.

[0150] Without being limited by theory, it is believed that pulsing delivers less energy to the rock surface than continuous energy and as such, diminishes the material removed.

[0151] The trials constituted multiple traverses over the same surface. The term track offset refers to the lateral distance the laser moves between passes. For a square laser beam with an offset the same as the laser size, the paths traversed by adjacent laser beams are adjacent. Where a circular laser beam is used, it is anticipated that the track offset will be less than the laser beam.

[0152] The best results were observed for runs 35 and 38. In run 35, 1.1 kg of granite was removed in 155 seconds (26.5 kghr.sup.−1) and in run 38, 1.7 kg of sandstone was removed in 155 seconds (40.8 kghr.sup.1). Trial results suggest that circular collimated beams with a diameter of approximately 20 mm to 40 mm are indicated. It was observed that spalled material was generally slightly smaller than the laser beam diameter. At a target of approximately 1 kWcm-2, laser powers of 3 to 12 kW for a round beam and 4 to 16 kW for a square beam are indicated.

TABLE-US-00001 TABLE 1 Granite, optic defocused to reach desired spot diameter, traverse path, meander Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms.sup.−1) (ms) (mm) of layers (mm) Observations 1 8 50 n/a 5 1 5 Spalling 2 8 75 n/a 5 1 5 Less spalling than run 1.

TABLE-US-00002 TABLE 2 Granite, optic defocused to reach desired spot diameter, work distance 280 mm, traverse path, meander Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms.sup.−1) (ms) (mm) of layers (mm) Observations 3 14 50 n/a 25 1 25 Spalling observed 4 12 50 100 25 1 25 100 ms on, 50 ms off; spalling 5 16 50 100 25 1 25 100 ms on, 50 ms off; spalling 6 14 50 100 25 1 25 100 ms on, 50 ms off; spalling 7 14 50 n/a 25 1 25 Increased spalling over run 6 8 14 50 100 25 4 25 100 ms on, 50 ms off; spalling 9 14 50 n/a 25 1 25 Increased spalling over run 7

TABLE-US-00003 TABLE 3 Granite, collimated beam, traverse path, 1 track Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms.sup.−1) (ms) (mm) of layers (mm) Observations 10 8 50 n/a n/a 1 50 Spalling observed 11 8 25 n/a n/a 1 50 More spalling than run 10 12 8 25 n/a n/a 4 50 Spalling observed 13 8 12.5 n/a n/a 4 50 More spalling than run 12 14 8 37.5 n/a n/a 4 50 Less spalling than run 13 15 8 50 n/a n/a 4 50 Less spalling than run 14 16 3 12.5 n/a n/a 4 50 Spalling observed 17 6 12.5 n/a n/a 4 50 Spalling observed; similar to run 13 18 12 12.5 n/a n/a 4 50 More spalling than run 17 19 16 12.5 n/a n/a 4 50 Highest amount of spalling for this table 20 16 12.5 100 n/a 4 50 100 ms on, 50 ms off; spalling

TABLE-US-00004 TABLE 4 Sandstone, collimated beam, traverse path, 1 track Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms.sup.−1) (ms) (mm) of layers (mm) Observations 21 8 12.5 n/a 50 1 50 Spalling observed 22 8 25 n/a 50 1 50 Spalling observed 23 12 12.5 n/a 50 1 50 More spalling than runs 21 or 22

TABLE-US-00005 TABLE 5 Basalt, collimated beam, traverse path, 1 track Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms.sup.−1) (ms) (mm) of layers (mm) Observations 24 8 100 n/a 50 1 50 Spalling observed 25 16 100 n/a 50 1 50 Spalling observed

TABLE-US-00006 TABLE 6 Granite, collimated beam, traverse path, meander Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms.sup.−1) (ms) (mm) of layers (mm) Observations 26 3.5 50 n/a 16 1 32 Spalling observed 27 8 12.5 n/a 16 1 32 More spalling than run 26 28 8 12.5 n/a 16 3 32 More spalling than run 26

TABLE-US-00007 TABLE 7 Granite, zoom optic, traverse path, meander Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms.sup.−1) (ms) (mm) of layers (mm) Observations 29 8 100 n/a 30 1 29 × 29 Spalling observed 30 16 100 n/a 30 1 29 × 29 More spalling than run 29 31 8 50 n/a 30 1 29 × 29 Spalling observed 32 8 25 n/a 30 1 29 × 29 Spalling observed 33 16 25 n/a 40 1 40 × 40 More spalling than run 32 34 16 12.5 n/a 40 1 40 × 40 More spalling than run 33 35 16 12.5 n/a 40 3 40 × 40 Highest amount of spalling for this table

TABLE-US-00008 TABLE 8 Quartz (lithum), zoom optic, traverse path, meander Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms.sup.−1) (ms) (mm) of layers (mm) Observations 36 16 n/a 1200 40 1 40 × 40 Spalling observed 37 16 n/a 2000 40 1 40 × 40 Spalling observed

TABLE-US-00009 TABLE 9 Sandstone, zoom optic, traverse path, meander Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms.sup.−1) (ms) (mm) of layers (mm) Observations 38 16 12.5 n/a 40 3 40 × 40 High degree of spalling