MINING METHOD

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.

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Description
TECHNICAL FIELD

This invention relates to development of a mining method to access and mine rock mineral deposits. The invention can also be applied to enhance conventional underground and open pit mining methods in certain applications.

BACKGROUND ART

The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

Conventional rock mining methods are generally characterised as entry methods in that personnel are required to attend in or near the mining face to facilitate excavation, equipment repair or other works. They are also generally characterised by machinery (mostly diesel or electric powered) that is usually manned, being deployed directly at the rock face to break and load the ore and transport it to a processing facility. Generally significant volumes of waste also have to be mined and transported in a similar manner to allow the personnel and equipment to access the ore. The mining almost universally takes place using a general cyclic process:

    • drill blast holes into the rock and load them with explosives;
    • evacuate the area of all personnel and critical equipment;
    • blast the rock;
    • ventilate the area and inspect it to ensure it is safe to continue mining;
    • redeploy equipment and personnel into the mining area and undertake any remedial works or ground support to ensure that it is safe to continue mining;
    • excavate the blasted rock, crudely separating ore and waste and haul the waste to the waste dump.
    • haul the ore to a stockpile for further sorting and or processing;
    • during the mining process the ore zone is sampled to identify the mineralised material for ore categorisation; and
    • repetition of the cycle.

Significant resources are expended on moving waste necessary to access the ore, and often ground stabilisation is required to ensure that the work areas are safe for personnel to access. Additionally, for narrow or stringy ore zones, waste may be mined with the ore that is unable to be excavated separately causing dilution to the ore.

The present invention seeks to overcome, or at least ameliorate, one or more of the deficiencies of the prior art mentioned above, or to provide the consumer with a useful or commercial choice.

SUMMARY OF INVENTION

In accordance with the present invention, there is provided 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.

Advantageously, the present invention expands the borehole in a direction radial to the axis of the borehole. In the context of the present specification, the term radial shall be understood to mean any direction that is not coaxial with the borehole axis.

Advantageously, it is possible to radially expand the borehole in targeted directions.

Advantageously, the step of expanding the borehole creates an open cavity.

Preferably, the step of fracturing the ore with the mining head comprises spalling or abrading the ore.

In one form of the invention, the steps of:

    • fracturing the ore; and
    • extracting the fractured ore to the surface;

are conducted simultaneously.

In one form of the invention, the steps of fracturing the ore and extracting the fractured ore to the surface are controlled at the surface of the earth.

In an alternate form of the invention, the steps of fracturing the ore and extracting the fractured ore to the surface are controlled underground.

In one form of the invention, the step of extracting the fractured ore through a borehole to a location remote from the mining head comprises extracting the fractured ore to the surface.

In the context of the present specification, the borehole containing a mining head may be referred to as a mining borehole and the borehole through which fractured ore is extracted may be termed an extraction borehole.

In one form of the invention, the mining borehole and the extraction borehole are the same borehole. In an alternate form of the invention, the mining borehole and the extraction borehole are different boreholes. Where the mining borehole and the extraction borehole are different boreholes, they are preferably adjacent.

The invention may utilise existing boreholes in the ground. Alternatively, the invention may comprise the additional step of forming a borehole in the earth.

In one form of the invention, the step of forming a borehole in the earth is conducted by conventional drilling techniques. In an alternate form of the invention, the borehole is formed by laser drilling.

The diameter of the borehole is preferably between 200 mm and 400 mm. In one form of the invention, the diameter of the borehole is about 200 mm. In an alternate form of the invention, the diameter of the borehole is about 300 mm.

The specific process used by the mining head to fracture the ore may take a number of forms depending upon the characteristics of the ore and its geometry, including 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.

In one form of the invention, the fractured ore is extracted in an extraction duct. It will be appreciated that the extraction duct should be large enough to accommodate fractured ore of varying size. In one form of the invention, the extraction duct is approximately half the diameter of the borehole.

In one form of the invention, the extraction duct is at least 20 mm diameter. In an alternate form of the invention, the extraction duct is at least 30 mm diameter. In an alternate form of the invention, the extraction duct is at least 40 mm diameter. In an alternate form of the invention, the extraction duct is at least 50 mm diameter. In an alternate form of the invention, the extraction duct is at least 60 mm diameter. In an alternate form of the invention, the extraction duct is at least 70 mm diameter. In an alternate form of the invention, the extraction duct is at least 80 mm diameter. In an alternate form of the invention, the extraction duct is at least 90 mm diameter. In an alternate form of the invention, the extraction duct is at least 100 mm diameter. In an alternate form of the invention, the extraction duct is at least 110 mm diameter. In an alternate form of the invention, the extraction duct is at least 120 mm diameter. In an alternate form of the invention, the extraction duct is at least 130 mm diameter. In an alternate form of the invention, the extraction duct is at least 140 mm diameter. In an alternate form of the invention, the extraction duct is at least 150 mm diameter.

In one form of the invention, the extraction duct is at 20 mm to 150 mm diameter. In an alternate form of the invention, the extraction duct is 30 mm to 150 mm diameter. In an alternate form of the invention, the extraction duct is 40 mm to 150 mm diameter. In an alternate form of the invention, the extraction duct is 50 mm to 150 mm diameter. In an alternate form of the invention, the extraction duct is 60 mm to 150 mm diameter. In an alternate form of the invention, the extraction duct is 70 mm to 150 mm diameter. In an alternate form of the invention, the extraction duct is 80 mm to 150 mm diameter. In an alternate form of the invention, the extraction duct is 90 mm to 150 mm diameter. In an alternate form of the invention, the extraction duct is 100 mm to 150 mm diameter. In an alternate form of the invention, the extraction duct is 110 mm to 150 mm diameter. In an alternate form of the invention, the extraction duct is 120 mm to 150 mm diameter. In an alternate form of the invention, the extraction duct is 130 mm to 150 mm diameter. In an alternate form of the invention, the extraction duct is 140 mm to 150 mm diameter.

In one form of the invention, the extraction duct is about 100 mm diameter. In an alternate form of the invention, the extraction duct is about 110 mm diameter. In an alternate form of the invention, the extraction duct is about 120 mm diameter. In an alternate form of the invention, the extraction duct is about 130 mm diameter. In an alternate form of the invention, the extraction duct is about 140 mm diameter. In an alternate form of the invention, the extraction duct is about 150 mm diameter. In an alternate form of the invention, the extraction duct is about 160 mm diameter. In an alternate form of the invention, the extraction duct is about 170 mm diameter. In an alternate form of the invention, the extraction duct is about 180 mm diameter. In an alternate form of the invention, the extraction duct is about 190 mm diameter. In an alternate form of the invention, the extraction duct is about 200 mm diameter.

Ore fractured in accordance with the present invention, may comprise fragments in the order of 1 to 20 mm in diameter.

In one form of the invention, the method comprises the further step of:

    • cooling the mine face.

In one form of the invention, the step of cooling the mine face is conducted simultaneously with the step of spalling the ore. In a second form of the invention, the step of cooling the mine face is conducted subsequently to the step of fracturing the ore.

Advantageously, cooling of the mine face facilitates spalling of the ore.

The mine face may be cooled by application of a gas stream or a liquid stream, for example water. Preferably, the mine face is cooled with compressed air. It will be appreciated that the step of delivering compressed air to a mine face may comprise delivering pulsed air or a constant air source.

In one form of the invention, the mining head comprises a laser mining head.

The laser mining head is in communication with a laser source located remotely from the laser mining head. In one form of the invention, the laser mining head and the laser source are connected by an optical fibre.

Preferably, the method comprises the further step of generating and delivering a laser beam to a mine face.

In the context of the present invention, the term mine face shall be understood to mean the surface where the mining work is advancing.

Preferably, the step of fracturing the ore is performed by a laser mining head.

The step of delivering a laser beam to the mine face advantageously causes fracturing of the ore into fragments. When the high intensity laser beam is applied to the mine face, the temperature of the ore rapidly increases. This rapid temperature rise causes thermal stresses in the ore and subsequent spalling. Spalling may be further enhanced and assisted by simultaneously (or after a short delay) applying a cooling agent to the mine face. Cooling can be achieved using a blast of compressed air or other gasses and can be assisted by moisture in the ore or at the mine face.

Spalling may also be enhanced by mechanical action on the face.

In one form of the invention, there is provided the additional step of:

    • mechanical action on the face either simultaneously with or subsequent to the step of fracturing the ore with the mining head

While the temperature required to effect spalling of the ore will vary according to ore type, 450° C. to 900° C. should be sufficient. Care should be taken to avoid melting of the ore. In one form of the invention, the laser beam heats the mine face to about 600° C.

It will be appreciated that the temperature rise in the rock surface will be affected by the combination of the power density of the laser and the duration of exposure of the rock to the laser. Different types of rocks will require different time frames to achieve a desired temperature rise due to the combination of materials in their composition and their colour, noting that darker materials tend to absorb more light energy than lighter materials.

The temperature may be controlled by a combination of laser power for a given spot size and exposure time.

The laser beam may be focused into different shapes such as square, rectangular or oval to optimize the spalling conditions.

The laser beam diameter at the mine face may be between 1 and 100 mm. In one form of the invention, the laser beam diameter is between 1 and 40 mm. In one form of the invention, the laser beam diameter is between 1 and 30 mm. In an alternate form of the invention, the laser beam diameter is between 1 and 20 mm. In an alternate form of the invention, the laser beam diameter is between 1 and 10 mm. In an alternate form of the invention, the laser beam diameter is between 1 and 5 mm. In an alternate form of the invention, the laser beam diameter is between 1 and 2 mm. In an alternate form of the invention, the laser beam diameter is between 5 and 40 mm. In an alternate form of the invention, the laser beam diameter is between 5 and 30 mm. In an alternate form of the invention, the laser beam diameter is between 5 and 20 mm. In an alternate form of the invention, the laser beam diameter is between 5 and 10 mm. In an alternate form of the invention, the laser beam diameter is between 10 and 40 mm. In an alternate form of the invention, the laser beam diameter is between 10 and 30 mm. In an alternate form of the invention, the laser beam diameter is between 10 and 20 mm. In an alternate form of the invention, the laser beam diameter is between 20 and 40 mm. In an alternate form of the invention, the laser beam diameter is between 20 and 30 mm.

Laser sources of different power may be operated at different diameters and distances.

The laser mining head is in communication with a laser source with an output power range of 1 to 60 kW. In one form of the invention, the laser source has an output power range of 1 to 50 kW. In an alternate form of the invention, the laser source has an output power range of 1 to 40 kW. In an alternate form of the invention, the laser source has an output power range of 1 to 30 kW. In an alternate form of the invention, the laser source has an output power range of 1 to 20 kW. In an alternate form of the invention, the laser source has an output power range of 1 to 10 kW. In an alternate form of the invention, the laser source has an output power range of 1 to 5 kW. In an alternate form of the invention, the laser source has an output power range of 10 to 50 kW. In an alternate form of the invention, the laser source has an output power range of 10 to 40 kW. In an alternate form of the invention, the laser source has an output power range of 10 to 30 kW. In an alternate form of the invention, the laser source has an output power range of 10 to 20 kW. In an alternate form of the invention, the laser source has an output power range of 20 to 50 kW. In an alternate form of the invention, the laser source has an output power range of 20 to 40 kW. In an alternate form of the invention, the laser source has an output power range of 20 to 30 kW. In an alternate form of the invention, the laser source has an output power range of 25 to 30 kW. An example of a suitable laser is a Laserline LDM 5,000 W laser unit.

It will be appreciated that the power applied to the mine face by the laser mining head may be less than the power of the laser source. This can be affected, for example, by the distance between the laser source and the laser mining head.

Preferably, the laser applied to the mine face has a power range of about 1.5 to 2.5 kW. In one form of the invention, the laser has a power of about 1.5 kW. In an alternate form of the invention, the laser has a power of about 1.6 kW. In an alternate form of the invention, the laser has a power of about 1.7 kW. In an alternate form of the invention, the laser has a power of about 1.8 kW. In an alternate form of the invention, the laser has a power of about 1.9 kW. In an alternate form of the invention, the laser has a power of about 2.0 kW. In an alternate form of the invention, the laser has a power of about 2.1 kW. In an alternate form of the invention, the laser has a power of about 2.2 kW. In an alternate form of the invention, the laser has a power of about 2.3 kW. In an alternate form of the invention, the laser has a power of about 2.4 kW. In an alternate form of the invention, the laser has a power of about 2.5 kW.

The laser beam is preferably in the infrared range of the electromagnetic spectrum. In one specific form of the invention, the laser beam has a wavelength of about 1000 nm

It will be appreciated that fracturing of an ore body will provide fragments of certain sizes. Advantageously, it is possible with laser spalling to control the size of ore fragments by the tracking sequence. Further, the size of the ore fragments may be controlled such that the need for further processing on the surface is reduced. Without being limited by theory, it is believed that ore fragments are generally slightly smaller than the diameter of the laser beam.

In a highly specific form of the invention, the mine face is irradiated with a constant source of laser beam. In such an embodiment, the laser mining head travels continuously over the mine face. The speed of movement is calculated to provide the desired dwell time. A source of compressed air follows the pattern of the laser mining head and applies cooling air to the irradiated site to rapidly cool the irradiated ore.

In a highly specific form of the invention, the mine face is irradiated with a laser pulse for a desired dwell time. Subsequent to the pulse, the laser mining head moves to a location on the mine face adjacent to that just irradiated and repeats the process. A source of compressed air follows the pattern of the laser mining head and applies cooling air to the irradiated site to rapidly cool the irradiated ore.

The dwell time of a laser on the mine face is a measure of the relationship or the laser power density and the speed of traverse of the laser beam over the mine face. The dwell time may be between 1 ms and 2000 ms. It will be appreciated that different dwell times may be appropriate depending on the power density.

For a circular laser beam with a surface area of 25 mm2 and a speed of traverse of 25 mms−1, the dwell time is 1 s. Lower dwell times are preferred as they enable quicker mining. Preferably, the dwell time is in the order of milliseconds.

In one form of the invention, the mining head comprises a water mining head.

The water mining head is in communication with a water and abrasion source located remotely from the water mining head. The water source may contain a system to deliver water to the mining head at a high pressure of for example, 200 MPa to 700 MPa. In one form of the invention, the water mining head and the water and abrasion source are connected by a delivery tube system. The water mining head may be provided with a mixing system to combine the abrasive and the water.

The step of delivering a water jet to the mine face advantageously causes fracturing of the ore into fragments. When the high pressure water is applied to the mine face, the water causes cracking and micro cracking of the ore. Water then penetrates the cracks and causes the ore to spall from the mine face due to the water pressure within the cracks exceeding the tensile strength of the ore.

In one form of the invention, the method comprises the further step of:

    • adding abrasives to the water.

Advantageously, the abrasives can facilitate the spalling of the ore. Suitable abrasives can include industrial grade garnet powders or grit.

In one form of the invention, the mine face is blasted with a water jet infused with garnet. In such an embodiment, the water mining head travels continuously over the mine face. The speed of movement is calculated to provide the desired dwell time to spall the ore.

In one form of the invention, the mining head comprises a flame mining head.

The flame mining head is in communication with a fuel source located remotely from the flame mining head. In one form of the invention, the flame mining head and the fuel source are connected by a delivery tube system. The flame head may be provided with an ignition system to remotely light the fuel to generate the flame.

The step of delivering a heat in the form of a flame to the mine face advantageously causes fracturing of the ore into fragments. When the heat is applied to the mine face, the temperature of the ore rapidly increases. This rapid temperature rise causes thermal stresses in the ore and subsequent spalling. Spalling may be further enhanced and assisted by simultaneously (or after a short delay) applying a cooling agent to the mine face. Cooling can be achieved using a source of compressed air or other gases and can be assisted by moisture in the ore or at the mine face. The source of cooling may be continuous or intermittent.

Spalling may also be enhanced by mechanical action in the face.

In one form of the invention, there is provided the additional step of:

    • mechanical action on the face either simultaneously with or subsequent to the step of fracturing the pre with the mining head.

While the temperature required to effect spalling of the ore will vary according to ore type, it is believed that 450° C. to 900° C. should be sufficient. Care should be taken to avoid melting the ore. In one form of the invention, the flame heats the mine face to about 600° C.

The flame may be fed by a high heat-flux density heating gas such as oxy-acetylene or other slower burning gasses such as propane or natural gas or liquid hydrocarbons such as diesel fuel.

In one form of the invention, the mining head comprises mechanical means to fracture the ore. Mechanical means may include a percussion hammer such as a Montabert SC6 Hydraulic Rock Breaker or equivalent thereof or a mechanical cutter head such as a Simex TF200 Double Drum Cutter Head or equivalent thereof. Such means may be powered pneumatically or hydraulically or electrically.

The step of extracting the fractured ore to the surface may be conducted by air vacuum suction, venturi, water injection and slurry pumping, mud injection and density floatation, mechanical means or combinations thereof.

In one form of the invention, there is provided a twin tube pipe system where a fluid such as compressed air of variable volume and pressure is pumped down the outer annulus of a twin tube pipe within the cluster of service inner tubes and then redirected by a compressed air crossover at the down hole end of the twin tube pipe which redirects the compressed airflow back up the inner tube thereby creating sufficient negative pressure to create a vacuum effect of sufficient capacity at the end of pipe to withdraw the spalled fragments up the inner tube from the mining area to the surface

In an alternate form of the invention, there is provided a single tube pipe system within the cluster of service inner tubes where a vacuum negative pressure is applied to the top of that pipe at the surface of the borehole to create a suction at the downhole end of pipe of sufficient capacity to extract the spalled fragments up the pipe from the mining area.

In an alternate form of the invention, fragments are removed by flotation using specialist density fluids such as drilling fluids which are directed via pipes within the cluster of service inner tubes to the bottom of the extraction void created as spalled rock breaking takes place. The fluids will hold the spalled rock particles in fluid suspension for extraction by vacuum, venturi or pumping methods singularly or in any combination.

The step of extracting the fractured ore to the surface may be conducted in the same bore hole as the step of introducing a mining head into a borehole or in a different borehole.

Advantageously, it is not necessary to fracture all of the material surrounding a borehole all the way to the surface. The present invention enables the user to target ore under the surface and only fracture the material of interest. The mining method is highly selective.

In one form of the invention, determination of the location of the material of interest comprises mapping the orebody geometry using conventional drilling, survey, seismic, 3D software modelling (e.g. Surpac, Micromine) techniques.

In an alternate form of the invention, determination of the location of the material of interest comprises visual inspection. In some circumstances, valuable ore is a visually different rock type to surrounding waste material. With the assistance of a camera at the mine face, a user can visually target the desired material. Alternatively, non-visual electromagnetic radiation may be used such as the CSIRO ExScan 3D laser scanning device. Alternatively, infrared scanning can be used to differentiate materials. An exemplary device would be a FLIR A615 infrared unit (https://www.flir.com.au/products/a615).

In one form of the invention, the mining head is provided with means to conduct elemental analysis of the mine face. Preferably, the means to conduct elemental analysis of the ore fragments is to use a spectral analysis system, for example an infrared emitter/receiver. Analysis of the mine face enables a surface located operator to identify the presence or absence of target ore.

In one form of the invention, the mining head is provided with means to illuminate the mine face.

In one form of the invention, the mining head is provided with means to monitor and record operations.

The present invention offers numerous advantages over the prior art including the conduct of all operations remotely and particularly, from the surface with no personnel underground or at the mining face, no requirement for the installation of ground support, no requirement to maintain an atmosphere suitable for human activity at the mine face and recovery of the ore fragments as a pre-crushed product. The present invention also offers significantly reduced environmental and ethnographic impacts and significantly reduces site water consumption.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

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

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

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

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

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

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

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

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

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

 DESCRIPTION OF EMBODIMENTS

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.

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.

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.

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.

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.

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.

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.

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

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The present invention provides the following advantages:

    • optimisation of ore recovery;
    • less dilution from the surrounding rock;
    • reduction in capital expenditure on mine development;
    • 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;
    • a small area of surface disturbance required for the mining operation lowering the environmental impact of the works; and
    • all access and broken ore retrieval is undertaken through a borehole;

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:

    • LDF 16000—60. Variable output 2 to 16 kW;
    • FOC—600 μm;
    • Lens Arrangement 1—OTS-5 optic arrangement with collimating (50 mm) and focusing lens, circular spot. Side mount camera;
    • Lens Arrangement 2—OTZ-5 optic arrangement with collimating and focusing lens, square spot;
    • Lens Arrangement 3—OTS-4 optic arrangement with collimating lens (32 mm), circular spot;
    • Laser Mount—Kuka RL80 multi axis, digitally controlled robot mount (ROB01) and fixed worktable;
    • Vacuum fume extraction system; and
    • Compressed air lance (nominal 100 psi) focused upon the exposure area moving in lock step with the laser.

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

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.

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.

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.

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−1) and in run 38, 1.7 kg of sandstone was removed in 155 seconds (40.8 kghr1). 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 1 Granite, optic defocused to reach desired spot diameter, traverse path, meander Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms−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 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−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 3 Granite, collimated beam, traverse path, 1 track Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms−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 4 Sandstone, collimated beam, traverse path, 1 track Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms−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 5 Basalt, collimated beam, traverse path, 1 track Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms−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 6 Granite, collimated beam, traverse path, meander Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms−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 7 Granite, zoom optic, traverse path, meander Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms−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 8 Quartz (lithum), zoom optic, traverse path, meander Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms−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 9 Sandstone, zoom optic, traverse path, meander Pulse Track Spot Power Speed Duration Offset Number diameter Run (kW) (mms−1) (ms) (mm) of layers (mm) Observations 38 16 12.5 n/a 40 3 40 × 40 High degree of spalling

Claims

1. A method of mining comprising the steps of: 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.

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;

2. A method of mining in accordance with claim 1, wherein the steps of: are conducted simultaneously.

fracturing the ore with the mining head; and
extracting the fractured ore through a borehole to a location remote from the mining head;

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.

Patent History
Publication number: 20220010626
Type: Application
Filed: Nov 15, 2019
Publication Date: Jan 13, 2022
Inventors: Robert John Morrow (Rossmoyne), Ross Harpur Thomson (Mount Lawley), Paul Jason Cabassi (Wembley), Christopher George Mardon (Wembley), Fraser Thomas Robert Morrow (Rossmoyne)
Application Number: 17/294,623
Classifications
International Classification: E21B 7/15 (20060101); E21B 17/20 (20060101); E21B 21/01 (20060101);