WO1996030629A1

WO1996030629A1 - The continuous mining, transport amd treatment system

Info

Publication number: WO1996030629A1
Application number: PCT/AU1996/000174
Authority: WO
Inventors: Robert Barwise Devereux; Alexander Hamilton Gray
Original assignee: Sedimentary Holdings Nl
Current assignee: Sedimentary Holdings Nl
Priority date: 1995-03-31
Filing date: 1996-03-29
Publication date: 1996-10-03
Anticipated expiration: 1997-09-30
Also published as: AUPN211395A0

Abstract

A mobile assembly (2) for continuously mining rock, sizing it and converting it to a slurry for pumping to a treatment station (3). The mobile assembly includes a continuous mechanical miner (5) arranged to cut rock with the cutting head (6), gather it onto the conveyors (10 and 24) and transport it to a hammer mill (26) which crushes and sizes the rock before allowing it to drop into a mixing chamber (41) through an eductor (44) to be turbulently mixed with water, converted to a slurry and pumped to a treatment station (58).

Description

TITLE: THE CONTINUOUS MINING, TRANSPORT AND TREATMENT SYSTEM FIELD OF THE INVENTION

This invention relates to a method and assembly for mining and in a particular aspect relates to an integrated mining and processing arrangement suitable for developing valuable rock deposits, particularly rock deposits including low grade ores. BACKGROUND OF THE INVENTION

The mining and treatment of rocks such as ores is carried out using many different methods. Whether the approach to mining involves an open cut mine or an underground mine, generally speaking, the rock being mined is removed from the rock body using appropriate mechanical equipment or explosives. It may then be harvested and transported to an area for stockpiling prior to being put through a treatment plant for extracting the desirable components of the rock.

Such approaches give a reasonably satisfactory result for most situations. However, one disadvantage from which many of such processes suffer relates to their stepwise nature. As a result of using several discontinuous steps, the amount of handling required may be relatively costly in terms of labour and capital equipment. Additionally, the need to stockpile may take up valuable land space.

Another disadvantage of the stockpiling approach is that it is difficult to maintain security over a large stockpile without resorting to expensive security precautions such as extensive and costly fencing and surveillance. The security aspect is of particular concern in situations where rocks being mined contain very valuable materials such as chunks of gold or precious gems.

Thus there is a need for the development of processes and machinery which can mine rock deposits without requiring stockpiling of the rock and/or which do not involve a series of discontinuous steps. DISCLOSURE OF THE INVENTION

In one embodiment the invention provides a continuous method for mining rocks including the steps of: transferring rock from a rock body to a sizing station; comminuting and sizing the rock at the sizing station; mixing the sized rock with water to form a pumpable slurry; and pumping the slurry to a rock treatment station.

In another embodiment the invention provides a mobile assembly for continuously mining rocks including: a continuous mining machine for mining rock from a rock body; a rock crusher adapted to receive rock from the continuous mining machine and to crush the rock. sizing means for sizing the rock; a mixer for mixing water with the sized rock to form a pumpable slurry; conduit means for transferring the pumpable slurry to a rock treatment station; and drive means for moving said continuous mining machine. PREFERRED ASPECTS OF THE METHOD OF THE INVENTION

The rock is preferably mined by continuously breaking the rock from a rock body. The breaking of the rock may form a tunnel, shaft or stope underground. Rock from the breaking step may be allowed to fall to the floor of the excavation formed in this manner. Subsequently, rock may be picked up from the floor of the resultant underground excavation and conveyed to a crushing and sizing station.

As a safety measure, the conveyed rock may be subjected to magnetic separation to remove any unwanted magnetic material such as broken pieces of metal from the continuous mining machine.

Oversized pieces of rock may be separated from the rock. The separated oversized rock pieces may be returned to the floor of the excavation. Preferably the oversized rock is separated prior to the rock reaching the crushing and sizing station.

At the crushing and sizing station, rock may be crushed. The crushed rock may be subjected to a sizing step. The sizing step may ensure that a substantial proportion of the rock falls below a predetermined particle size. Preferably at least 90% by weight of the rock after the sizing step is composed of particles having a maximum dimension less than 25 millimetres more preferably less than 15 millimetres. However for some mineral products such as coal, sizes greater than 25 mm may be desirable.

The sizing step may be achieved by passing the crushed rock through a grate. The grate may have a plurality of grate elements. Preferably the separation between the grate elements is between 0.1 millimetres and 25 millimetres more preferably 1 millimetre to 15 millimetres.

After sizing, the rock may be subjected to a wetting step. Wetting may be achieved by spraying or sprinkling with water or by immersion in water. The wetting step is preferably carried out by allowing the sized rock to become immersed in water. The water may be contained in a tank or reservoir. The wetting step is preferably carried out prior to forming a pumpable slurry of the rock.

The pumpable slurry may be formed by agitating the sized rock with water. Such agitation may be achieved by directing a flow of water under pressure to a mixing chamber and mixing sized rock with the water in the mixing chamber. The rock may be formed into a pumpable slurry using an cductor. Viscosity modifiers may be added to the slurry to improve its properties for processing and/or transport. In particular, viscosity modifiers may be added to improve pumpability.

Conduit means may be arranged to receive pumpable slurry from the eductor. The conduit means may be arranged to deliver the slurry to a treatment station. The treatment station may be below or above ground. Slurry may be pumped from the tunnel to the treatment station which may be located in the tunnel or above ground.

The treatment station may be used to separate desired materials from the slurry. Preferably the treatment station separates dense particulates from the slurry. The treatment station may separate dense particulates from the slurry using the method described in the Specification of Patent Co-operation Treaty International Patent Application PCT/AU95/00137 entitled "Separator", in the name of Alexander Hamilton Gray.

Excess water and tailings arising from treatment of the slurry at the treatment station may be directed into a tailings dam. Water from the tailings dam may be recycled for use in the method.

Desired materials separated from the slurry at the treatment station may be subjected to further treatment steps. For example, where it is desired to separate dense particulates from the slurry, using the separator or separation method described in the aforesaid PCT Application, the dense particulates may be subjected to further concentration by a processing step such as centrifuging.

The method of the invention may be particularly suitable for gold recovery, especially, gold recovery from low grade gold ores. It is anticipated that the method may be used to recover gold from ores containing less than 2 grams of gold per tonne of ore and even from ores containing less than 1 gram of gold per tonne of ore. Such ore grades may generally relate to underground mining.

Where open cut mining is being considered using the continuous method of the invention, it is anticipated that gold ores containing less than 0.5 grams of gold per tonne of ore may be feasible and even ores containing less than 0.25 grams of gold per tonne of ore might even be economically possible.

The method of the invention may also be suitable for mining rock dcposiLs including any one or more of coal, precious stones, industrial minerals and tin. PREFERRED ASPECTS RELATING TO THE MOBILE ASSEMBLY OF THE INVENTION

The continuous mining machine may have means for breaking the rock of an ore body. The means for breaking may include a cutting rotor. The cutting rotor may be mounted on a turret. The turret av be movcablc vertically and horizontally . The turret may move the cutting rotor in such a manner as to cut out an underground excavation. The excavation may be defined by the forward movement of the mobile assembly cutting through the rock. The excavation may be in the form of a tunnel or stope.

The continuous mining machine may be a continuous mechanical miner.

Gathering means may be provided in association with the continuous mining machine for gathering rock broken from the rock body. The gathering means may include one or more gathering arms. The gathering arms may protrude forward of the continuous mining machine. The gathering arms may be mounted on the continuous mining machine. The gathering arms may form a ramp which serves to push the rock upwards and onto conveyor means as the continuous mining machine moves forward.

The conveyor means may include a primary conveyor and a secondary conveyor. The primary conveyor may be arranged to lift rock and to deliver it to the secondary conveyor. The primary conveyor may be mounted on the continuous mining machine.

The continuous mining machine may include an operator's cabin, controls and drive motor. The continuous mining machine may be mounted on a drive assembly. The drive assembly may include wheels and/or tracks.

The conveyor means may be arranged to deliver rock to the rock crusher. Removal means may be associated with the mobile assembly. The removal means may be adapted to remove magnetic material from the rock. The removal means may include a magnet. Preferably the magnet is an electromagnet. The removal means may be mounted above the conveyor means in a manner which facilitates removal of magnetic material from rock being transported on the conveyor means.

Reject means may be associated with the mobile assembly. The reject means may be adapted to discard oversize lumps of rock. The reject means may comprise a screen or grate. The reject means may be mounted on the rock crusher or between the primary and secondary conveyor. Preferably the reject means includes a screen or grate arranged between the primary and secondary conveyor.

The conveyor means may be arranged to deliver rock to the rock crusher. Preferably the rock crusher is a hammer mill. The rock crusher may include sizing means. The sizing means may be constructed to ensure that rock exiting from the crusher has a particle size substantially below a predetermined limit. Preferably the particle size is less than 25 millimetres more preferably less than 15 millimetres.

The sizing means may comprise a screen or grate. Most preferably the sizing means comprise a grate having a plurality of graie members. The grate members may be elongate. The elongate grate members may be arranged parallel to each other, the spacing between the grate members defining the maximum particle size of rock exiling the rock crusher. The sizing means arc prclcrably provided at the bottom ol the rock crusher in order to allow crushed rock to fall out of the rock crusher through an outlet defined by the sizing means.

Mixing means may be arranged to receive sized rock from the rock crusher. The mixing means may be located beneath the rock crusher. The mixing means may include wetting means for wetting sized rock. The wetting means may comprise a tank or reservoir of water. The wetting means may promote wetting of the sized rock by spraying or immersion of the sized rock. Where the wetting means includes a tank of water, the tank may be arranged to submerge sized rock in water. The wetting means may include a cone. The wetting means may be mounted beneath the outlet of the rock crusher. The cone may be arranged to receive sized rock from the rock crusher and to direct the sized rock to eduction means. The cone may be arranged to submerge the sized rock in water contained in the tank. The mixer may include eduction means arranged to receive sized rock from the crusher. The cone may be arranged to direct the sized rock to the eduction means.

The eduction means may include an introduction port. The introduction port may include an opening arranged to receive sized rock from the cone. The other end of the introduction port may include a nozzle with a delivery opening for delivering sized rock there through.

The mixing means may include a mixing chamber. The delivery opening of the nozzle may protrude into the mixing chamber. The arrangement of rock crusher, cone, introduction port and mixing chamber may be such that rock travels through a substantially vertical drop from the rock crusher to the mixing chamber.

The mixing chamber may include water supply means for supplying water under pressure to the chamber. The chamber may be shaped and arranged to ensure that water from the water supply means mixes turbulently with the sized rock entering the mixing chamber to form a pumpable slurry. A primary pump may be provided to pump slurry from the mixing chamber into a transfer pipe.

Any one or more of the individual components of the assembly described hereinabove starting from the secondary conveyor up to the transfer pipe may be mounted on a mobile trailer. Preferably all these individual components are mounted on the trailer.

The trailer may be connected to the continuous mining machine. The continuous mining machine may be arranged to draw the trailer along via a tow-hitch. The trailer may include clearing means for pushing aside oversized lumps rejected by the reject means. The clearing means may include one or more blades mounted on the underside of the trailer.

Preferably the height of the mobile assembly is less than 5 metres. More preferably the height of the mobile assembly is less than 4 metres. The mobile assembly may be connected to surface pumping means for pumping slurry to the surface. The surface pumping means may be connected to the transfer pipe. The surface pumping means may comprise one or more high lift pumps. The arrangement may be such that slurry pumped to the surface may be pumped to a treatment station. The treatment station may include one or more separators of the type described hereinbefore in relation to the PCT Patent Application by Alexander Hamilton Gray. Preferably there are two such separators. The separators may be arranged in series or in parallel.

The separators may be associated with secondary separation means. The secondary separation means may comprise one or more centrifuges. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanying drawings wherein:

Figure 1 shows an elevational view of a mining plant constructed in accordance with the invention;

Figure 2 shows an elevational view of a crushing and slurry generating facility termed a "slurry assembly";

Figure 3 shows an expanded sectional view of the hammer mill and slurry generation section of the slurry assembly of Figure 2.

Figure 4 shows a schematic view of a control system for the mining plant shown in Figure 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Figures 1 to 3 of the accompanying drawings, the mining plant generally designated 1, includes a mobile assembly 2 which consists of the continuous mechanical miner 5 and a slurry assembly 21 joined together to move in tandem by the tow-hitch 20.

The mobile assembly is arranged to harvest and transfer rock in the form of slurry to the rock treatment station 3.

A tailings dam 4 is provided to dispose of unwanted solids and provide a means of recycling water.

The continuous mechanical miner 5 includes a cutting head 6 mounted on a turret 7. The turret is arranged to move the cutting head in both vertical and horizontal directions to cut out the mine face 8 and hence define the dimensions of the excavation 12 as the mobile assembly moves forward.

One or more gathering arms 9 arc mounted on the front of the continuous mechanical miner to gather rock which has been cut by the cutting head and fallen to the floor of the tunnel. Thus, it can be seen that the gathering arm 9 is in the form of a ramp which pushes up the rock onto a conveyor 10 which extends from the gathering arm to the rear of the mobile assembly.

The continuous mechanical miner body 11 houses an operator's cabin motors and controls for the mobile assembly. The track assembly 13 upon which the continuous mechanical miner is supported includes a motor to drive the continuous miner forward while at the same time pulling the slurry assembly 21 forward as well.

The slurry assembly 21 which is connected to the continuous mechanical miner by the tow-hitch 20 is itself mounted on a trailer 22 which moves along on the track assembly 23.

The rear of the conveyor 10 of the continuous mechanical miner is arranged to drop rock onto the conveyor 24 provided at the front of the trailer 22. A screen 14 interposed between the conveyor 10 and conveyor 24 is arranged to prevent oversized lumps of rock being taken up by the conveyor 24. Thus, these oversized lumps fall onto the ground.

An electromagnet 25 is mounted above the rock travelling on the conveyor 24 to remove any unwanted magnetic materials which may have broken off from the continuous mechanical miner.

The conveyor 24 is arranged to lift rock to the inlet 28 of the hammer mill generally designated 26.

The hammer mill includes a housing 29, rotor 30 and a plurality of hammers 31. The rotor/hammer assembly is driven by the motor 32 via the drive belt 33.

The bottom of the hammer mill is provided with a grating 34 having a plurality of parallel bars which are separated by a predetermined distance to ensure that only particles below a predetermined size fall out of the hammer mill through the grating.

A hopper 35 is arranged beneath the grating to receive sized rock falling there through, the hopper having a cone 36 provided at the lower portion thereof.

The cone sits in a tank 37 which is filled with water to the water level 38. As the interior of the cone is in communication with the water in the tank, water level in the cone is maintained at the same level as that of the water in the tank.

An outlet 40 is provided at the bottom of the cone. The bottom of the cone is joined to and feeds sized rock into an cductor 44.

The eductor 44 includes a mixing chamber 41. a water pipe 39, an introduction port 46 and a Vcnturi tube 45. The water pipe 39 is arranged to clear passages in the cductor and the introduction port 46 delivers rock from the cone to the mixing chamber 41 of the cductor 44.

The mixing chamber is in communication with a pipe 42 arranged to supply water under pressure to the mixing chamber 41 where si cd rt -k exiting Irom the nozzle end of the introduction port 46 mixes turbulently with water from the water pipe 42 to form a pumpable slurry which may be pumped via the pipe 50 by the pump assembly 51.

The slurry assembly 21 may also include one or more blades 43 mounted beneath the trailer to push aside any oversized lumps of material which have been rejected by the screen 14.

A pipe 52 which should be sufficiently flexible to accommodate the forward movement of the mobile assembly joins with pipe 50 and is arranged to transfer the pumped slurry to the hopper 53.

One or more pumps 54, which may be high lift pumps, are arranged to pump the slurry from the hopper up the shaft 55 via pipe 56 to the surface.

A tank 57 may be provided on the surface to add extra processing water as and when required. The pipe 56 directs the slurry to the treatment plant on the surface which may include separators 58 of the type described in the Patent Co-operation Treaty International Patent Application by Alexander Hamilton Gray referred to hereinbefore. Following treatment by the separators, the concentrate from the separators may be subjected to further separation by one or more centrifuges 59.

The tailings dam includes a pipe 60 and pump 61 to recycle water from the dam.

During operation, the mobile assembly moves forward with the cutting head 6 cutting through rock. The cut rock is picked up by the gathering arms 9 and conveyed to an elevated position at the rear of the continuous mechanical miner 5 by the conveyor 10.

From this elevated position the conveyor 10 drops the mined rock onto the conveyor 24. The interposed screen 14 is arranged to reject oversized lumps of rock so that such lumps can fall to the ground. After being subjected to a magnetic separation process via the electromagnet 25 the conveyor 24 conveys the rock to the hammer mill 26 where it is sized and converted to a slurry in the cductor 44. The resultant slurry is then pumped to a hopper from whence it is pumped to the surface by lifting pumps 54 for treatment in a treatment plant.

The treatment plant includes two separators in scries which separate heavy particulates from the slurry after which the heavy particulates concentrate produced from the separators is subjected to the centrifuge 59 to complete the final separation.

Tailings from the process arc pumped into the tailings dam 4 where solids arc allowed to settle. Water from the tailings dam is recycled for further use in the process.

Referring to Figure 4. there is shown a schematic arrangement for controlling the operation of the mining plant shown in Figure 1

The schematic drawing is split into three main sections, namely a schematic arrangement contained within the box defined by the broken line 1⁽X⁾ lor controlling the mining crashing and conversion to slurry ol the mined rock, a controlling arrangement 101 for the main assembly pumps and a treatment and recycling station 200.

The mining and crushing unit 100 is controlled through a main controller 102 which can be arranged to control the functions of the mining and crushing unit automatically or may be manually controlled through the control panel 96.

The main controller 102 includes an incoming signals port 98 and an outgoing signals port 99. Furthermore, it is connected to a communication cable 97 which in turn connects to a further main control for the main pump unit 202 and an equivalent system in the treatment and recycling unit 200.

Turning to the unit 100, in the manner described herein before with reference to Figures 1 to 3, the cutting head 6 mines rock to be picked up by the conveyor 10. A sensor 105 which most suitably will be in the form of a current transformer monitors the power consumption of the cutter head and feeds this information to the main controller 102.

A further sensor 105 associated with the motor 103 sensors the power consumption and hence speed of the motor 103 and feeds this information to the main controller 102. In turn, the controller controls the motor 103 by way of the variable speed drive control 107.

Material from the conveyor 10 is transferred to the conveyor 24. The current consumption and hence speed of the motor 104 driving conveyor 24 is monitored by a further sensor 105. The conveyor 24 delivers rock to the crusher 26 in the form of a hammer mill and the speed at which the hammer mill is operated is monitored by a further sensor 105 in the form of a current transformer which measures the current consumption of the electric motor operating the hammer mill. Generally speaking, it is anticipated that the hammer mill will not have a variable speed and hence there will be no need for a variable speed drive controller. However, in some instances where a more flexible approach is required, it is to be understood that a variable speed drive control in association with the motor operating the hammer mill may be provided.

Crushed rock falls into the sump 37 and the level of crushed rock therein is sensed by a level control sensor 95. This in turn is connected to the variable speed drive control 107 controlling the operation of the pump assembly 51. The pump assembly is arranged to pump slurry formed in the cductor 40 to the pumping unit 101. A sensor 105 is also provided to sense the current consumption and hence pumping speed of the pumping assembly 51.

Water is supplied to the cductor by the water pipe 108. The water supply is regulated by the manual valve 214. pressure reducing valve 213. electrically actuated valve 106 and the two manual valves 109 which can be adjusted to correctly proportionate the relative amounts of water going to the tank/sump 37 and the cductor 40.

A scries of magnetic flow meters 1 10 monitor the rate of flow of fluid through the pipes 108 and 52. It is noted that there arc two magnetic flow meters on pipe 52. the first of these monitoring the amount of slurry exiting from the mining crushing unit 100 and the second monitoring the amount of fluid entering the main pump unit 101. By comparing the two flows rates recorded, it is possible to readily monitor any leakages which may be occurring between the two units and to respond thereto either manually or by setting the various controllers to automatic shut down mode. A density sensor 210 is also supplied in association with the pipe 52 conducting the slurry. If the density falls outside predetermined limits, the rate of water supplied to the eductor 40 can be altered by the electrically activated valve 106.

Slurry is delivered to the sump/hopper 53 by the pipe 52 and the level controller 207 senses and ensures that the level in the sump falls within the required limits. An electrically actuated valve 206 connected to the water pipe 108 is arranged to direct water into the sump 53 if the level should fall below predetermined limits.

Again, the operations of the main pump unit 101 are controlled by the main controller 202 having an outgoing signals port 203, and incoming signals port 204, a control panel 205 and a connection to the communication cable 97.

Slurry from the sump is pumped out of the tunnel via the two pumps 54 and the pipe 56 arranged in a shaft to deliver the slurry to the treatment and recycling unit 200.

Sensors 208 are arranged to sense the current consumption of the pumps 54 and the pumps are in turn controlled by the variable speed drive control 209.

A sump pump 211 may optionally be associated with the pump.

A flow sensor 212 associated with the pipe 56 sends signals to the controller 202 indicating the amount of slurry being pumped to the treatment and recycling unit.

The two controllers 102 and 204 together with any equivalent controllers in the treatment and recycling unit 200 may be set to interact electronically and automatically to ensure that the various elements of the mining plant are set to run in a coordinated fashion.

While it has been convenient to describe the invention herein in relation to particular preferred embodiments, it is to be appreciated that other constructions and arrangements are also considered as falling within the scope of the invention. Various modifications, alterations, variations and/or additions to the constructions and arrangements described herein arc also considered as falling within the ambit and scope of the present invention.

Claims

1. A continuous method for mining rocks including the steps of:- (i) transferring rock from a rock body to a sizing station; (ii) comminuting and sizing the rock at the sizing station;

(iii) mixing the sized rock with water to form a pumpable slurry; and (iv) pumping the slurry to a rock treatment station.

2. A method according to Claim 1 wherein the rock is mined by continuously breaking the rock from a rock body.

3. A method according to Claim 2 wherein the mining of the rock forms a tunnel, shaft or stope underground.

4. A method according to Claim 2 wherein the rock from the breaking step is allowed to fall to the floor of an excavation formed by the mining of the rock after which the rock is picked up from the floor and conveyed to the crushing and sizing station.

5. A method according to Claim 1 wherein the rock is subjected to a magnetic separation step to remove any unwanted magnetic material.

6. A method according to Claim 1 wherein the rock is comminuted at the sizing station to ensure that at least 90% by weight of the rock after the sizing step is composed of particles having a maximum dimension less than 25 millimetres.

7. A method according to Claim 6 wherein at least 90% by weight of the rock after the sizing step is composed of particles having a maximum dimension less than 15 millimetres.

8. A method according to Claim 6 wherein sized rock is subjected to wetting by spraying or sprinkling with water or by immersing in water.

9. A method according to Claim 6 wherein sized rock is mixed with water to form a pumpable slurry.

10. A method according to Claim 9 wherein the rock is agitated with water using an eductor.

11. A method according to Claim 9 wherein viscosity modifiers are added to the slurry to improve its properties for processing and/or transport and/or pumpability.

12. A method according to Claim 9 wherein conduit means are arranged to deliver the pumpable slurry to the rock treatment station.

13. A method according to Claim 12 wherein excess water and tailings arising from treatment of the slurry at the rock treatment station arc directed into a tailings dam and water from the tailings dam is recycled for use in the method.

14. A method according to Claim 12 wherein dense particulates in the pumpable slurry arc subjected to concentration at the rock treatment station.

15. A method according to Claim 1 when used for recovering gold. coal, precious stones, industrial minerals and/or tin.

16. A method according to Claim 14 when used to recover gold from ores containing less than 2 grams of gold per tonne of ore.

17. A method according to Claim 16 wherein the method of the invention is used for open cut mining to recover gold from ores containing less than 0.5 grams of gold per tonne of ore.

18. A mobile assembly for continuous mining of rocks includin :-

(i) a continuous mining machine for mining rock from a rock body;

(ii) a rock crusher adapted to receive rock from the continuous mining machine and to crush the rock;

(iii) sizing means for sizing the rock;

(iv) a mixer for mixing water with the sized rock to form a pumpable slurry;

(v) conduit means connected to the mixer for transferring the pumpable slurry to a rock treatment station; and

(vi) drive means for moving said continuous mining machine.

19. A mobile assembly according to Claim 18 wherein the continuous mining machine includes breaking means for breaking the rock of an ore body.

20. A mobile assembly according to Claim 19 wherein the breaking means includes a cutting rotor mounted on a turret which is vertically and horizontally movable.

21. A mobile assembly according to Claim 19 wherein gathering means are provided in association with the continuous mining machine for gathering rock broken from the rock body and pushing the gathered rock onto conveyer means.

22. A mobile assembly according to Claim 21 wherein the gathering means include one or more gathering arms protruding forward of the continuous mining machine, the gathering arms forming a ramp which serves to push the rock upwards and onto conveyer means as the continuous mining machine moves forward.

23. A mobile assembly according to Claim 21 wherein the conveyor means includes a primary conveyor and a secondary conveyor, the primary conveyor being arranged to lift rock and to deliver it to the secondary conveyor.

24. A mobile assembly according to Claim 18 wherein the continuous mining machine is mounted on a drive assembly provided with wheels and/or tracks, the continuous mining machine including an operators cabin with controls for the drive assembly.

25. A mobile assembly according to Claim 22 wherein the conveyor means are arranged to deliver rock to the rock crusher.

26. A mobile assembly according to Claim 18 including reject means arranged to discard oversized lumps of rock.

27. A mobile assembly according to Claim 26 including a primary and a secondary conveyor, the primary conveyor being arranged to lift rock gathered by one or more gathering arms protruding forward of the continuous mining machine and to deliver the rock to the secondary conveyor, the secondary conveyor being arranged to deliver rock to the rock crusher.

28. A mobile assembly according to Claim 27 wherein the rock crusher is a hammer mill including sizing means arranged to ensure that crushed rock exiting from the crusher is sized to a particle size substantially below a determined limit.

29. A mobile assembly according to Claim 28 wherein the mixer includes wetting means mounted beneath the outlet of the hammer mill arranged to submerge sized rock exiting from the outlet in water and to deliver wetted rock therefrom to the mixing chamber of an eductor, the mixing chamber including water supply means for supplying water under pressure to the chamber, the chamber being shaped to ensure that water from the water supply means mixes turbulently with the wetted sized rock entering the mixing chamber to form a pumpable slurry prior to leaving the mining chamber via a transfer pipe connected to the mixing chamber.

30. A mobile assembly according to Claim 29 wherein the outlet of the hammer mill communicates with a conical member arranged to direct sized rock below the water level of water in a tank arranged above the eductor, the conical member being constructed to allow water from the tank to flow into the conical member at the same level as the water in the tank.

31. A mobile assembly according to Claim 30 including an introduction port for introducing wetted sized rock from the conical member to the mixing chamber and the transfer pipe is connected to the mixing chamber by a Venturi tube.

32. A mobile assembly according to Claim 18 wherein the components (ii), (iii) and (iv) are mounted on a trailer connected to the continuous mining machine via a tow-hitch and the height of the mobile assembly is less than 5 metres.

33. A mobile assembly according to Claim 32 wherein the height of the mobile assembly is less than 4 metres and the trailer includes one or more blades mounted on the underside of the trailer for pushing aside lumps of rock.

34. A mobile assembly according to Claim 18 including sensor means for sensing the rate of operation of the continuous mining machine, the rock crusher and the mixer and controller means responsive to signals from the sensor means to control operation of the mobile assembly.

35. A method according to Claim 1 wherein the rock is comminuted at the sizing station to ensure that at least 909F by weight of the rock after the sizing step is composed of particles having a maximum dimension greater than 25 millimetres.