AU592501B2 - Method and installation for mining - Google Patents

Description

AUSTRALIA

Patents Act 552501 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Tis dk0:mnt contains tlhe ai:;cdmenrts made under Section 49 and is correct for printing.

o a i q O Priority m 0 Related Art: 0 ta l Published: e s s t 4 r,a APPLICANT'S REF.: C.A.P. of PI 2169/87 LAWRENCE REGINALD BASTER Name(s) of Applicant(s): Address(es) of Applicant(s): 4 Dalgetty Road, Beaumaris, Victoria 3193, Australia Actual Inventor(s): Address for Service is: PHILLIPS, ORMONDE AND FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne, Australia, 3000 Complete Specification for the invention entitled: METHOD AND INSTALLATION FOR MINING The following statement is a full description of this invention, including the best method of performing it known to applicant(s): P19/3/84 This invention relates to an improved method and installation for mining below ground deposits of minerals, particularly alluvial deposits.

In some areas, precious minerals exist in relatively deep deposits, such as in ancient river beds. In Victoria, such deep lead alluvial gold deposits exist in river bed gravels between 30 to 60 million years old. The Victorian deep lead deposits range in thickness up to and exceeding metres, beneath an overburden of gravel, sand, clay and basalt of up to and exceeding 150 metres in depth. The depth of these deep lead deposits is generally such that open-cut mining is uneconomic, although some deposits have been successfully mined underground. Also, the areas in Victoria in which the deep leads are located typically are characterised by a high water table which precludes underground mining, since the permeability of the gravels precludes effective dewatering by use of pumping equipment.

,,,Old mining records indicate that up to two years dewatering could be necessary before underground mining became possible while, in one instance, water was pumped for six years before any payable gold bearing wash could be extracted.

The Victorian deep leads contain significant gold values and, as a consequence, there have been various proposals for mining these deposits. However, to date, none of the proposals has proved to be both operationally successful and environmentally acceptable. The present invention is directed to providing an improved method and %I 'installation suitable for mining such deposits, although the invention also is applicable to other forms of below ground, mineral deposits which are or can be substantially water saturated.

The present invention provides a mining method and tf installation based on the use of at least two mutually spaced bore holes which extend into a deposit from whichmaterial is to be mined. At least one of the bore holes has an outlet therefrom within the deposit, and is supplied with high pressure liquid to be discharged from the outlet into the deposit. At least one other of the bore holes has an inlet thereto within the deposit; the at least one other bore hole having pressurised gas supply means therein for discharge of pressurised gas therein to provide an air-lift action on aterial from the deposit caused to move toward the inlet under hydraulicking action of the liquid discharged from the at least one bore hole.

As a practical matter, the bore holes are cased, such as by casing in the form of a steel or plastics, such as polyethylene, pipe column. In each instance, the inlet or outlet will be defined by the respective casing. For ease of reference in subsequent description, the at least one bore hole provided with pressurised liquid will be referred to as the pressurising bore or bores; while the it least one further Sbore hole having gas sapply means will be referred to as the lift bore or bores, and the pressurising and lift bores will to~o S" be referred to collectively as the installation bores. Also, the pressurised liquid and gas typically will be water and air, respectively, as hereinafter specified.

The air-lift action provided in the lift bore acts in concert with hydraulicking action resulting from high pressure liquid discharged from the outlet of the pressurising f C C bore. The air-lift action comprises air-lift pumping of liquid in a column thereof generated in the lift bore by that hydraulicking action; the pumping being made possible by that rc column being hydraulicly connected at the bottom thereof to a column of liquid in the pressurising bore. The pumping aerates the liquid in the lift bore and, by virtue of a resultant reduction in the density of the liquid in the lift bore and a difference in pressure between the respective liquid columns, the pumping drives the liquid in the column in the lift bore upwardly. The strength of this pumping, and resultant pumping forces generated at the inlet of the lift bore, raises the column in the lift bore at substantial velocity, with material from the deposit being raised above ground level with that column.

The installation bores can vary substantially in diameter, depending on the size distribution of material comprising the deposit. In certain Victorian deep leads, the deposits can include quite large boulders, rarely exceeding 200 mm in diameter, and predominantly comprise water worn -3gravels with pebbles which seldom exceed 100 mm in diameter.

With such deposits, pressurising bores can be of up to 160 mm or more in diameter, while the lift bores can be up to 210 mm or more in diameter. In each case, for fine gravel, substantially smaller diameter bores can be used, depending in part on the number of and spacing between the pressurising and lift bores. However, the respective diameters indicated are suitable where one pressurising and one lift bore is used at a spacing therebetween of about 3 metres.

For the successful operation of the mining method water and air pressures and volumes will vary with the depth and nature of the mineral deposit to be mined, the height of the water table and the diameter of the installation bores to be used. For example, the deeper the deposit to be mined the greater the pressure of the air and water required. Also, the larger the installation bore diameters and/or the lower the water table, the greater the volume of water required. In ,general, likely broad ranges of water and air pressures for t mining deposits like the Victorian deep leads are:for water: from 275 Kpa to 2,750 Kpa (40 psi to 400 psi) tt for air: from 620 Kpa to 1,725 Kpa (90 psi to 250 psi) t *X Most conveniently at least two pressurising bores are used with each lift bore. Preferably the outlet of the or ("each pressurising bore is oriented so as to discharge water into the deposit in a direction towards the inlet of the lift bore. The outlet and inlet can be of substantial dimensions relative to its bore; the circumferential dimension of the outlet and inlet each being equal to or greater than its height dimension, and conveniently ranging from about one quarter to half the circumference of its bore.

The air supply means of the or each lift bore can take a variety of forms. In each case, it preferably discharges air into its lift bore a short distance above the inlet of the bore. In the case of a lift bore of about 150 to 160 mm. diameter, the air may be discharged about 750 to 2000 mm above the inlet, such as from about 1200 to 1700 mm above the inlet.

In one convenient arrangement, the air supply means is provided by a double wall length of the lift bore casing -4above the inlet thereof, which double wall defines an annular passage from the lower end of which pressurized air is able to be discharged into the lift bore. In such case, air preferably is discharged from an annular array of ports providing communication between the passage and the interior of the lift bore, although a single port may be used.

In an alternative arrangement, the air supply means may comprise at least one conduit extending longitudinally of, preferably within, its lift bore, for discharge of pressurized air into the interior of the lift bore. The or each such conduit preferably extends closely adjacent to the inner-surface of the lift bore.

SThe pressu'lsing bore functions to supply high pressure water to the deposit, and to move material of the Sdeposit towards the lift bore. The lift bore functions to suck in the material, and to lift it to above ground level.

However, the installation bores act in concert. Thus, the high velocity hydraulicking action of pressurised water from the pressurising bore is augmented hy the strong drawing power generated in the lift bore by the high velocity air-lift action produced by the pressurised air. The overall action Sreadily is able to raise solid material from the deposits to above ground level, through the lift bore. Indeed high density components of the deposit, such as gold from micron size to sizeable nuggets, are able to be raised, as also are lower density components up to sizeable boulders. The overall "tdriving force, principally generated by the pressurized air, yerr ,tLtresults in the solids, including gold nuggets and boulders,

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attaining high velocities such that the head of the lift bore above ground level preferably is curved or angled and discharges the solids into a suitable receiving area or facility.

The outlet of the pressurising bore and the inlet of the lift bore preferably are positioned adjacent the base of the deposit. This arrangement results in material being drawn from the deposit where gold values are highest, while material of lower values at higher levels will progressively be drawn down to the level of the inlet and outlet. However, if required, the installation bore casings may be progressively raised so as to draw material from the deposit at progressively higher levels. In each case, the inlet and outlet most preferably are on substantially the same level during a mining operation.

The installation bores preferably extend into basement rock below the deposit from which material is to be recovered. Where their casings are to be progressively raised, this may be accommodated by an end portion of each casing extending into the basement rock for a sufficient length such that, as it is raised, at least the lower end is retained in that rock. As will be appreciated, extending the casings into the basement rock secures them against forces prevailing during a mining operation.

Where the installation bores extend into basement rock, the outlet of the pressurising bore and the inlet of the lift bore each is positioned above the lower end portion of its bore. At least in the case of the pressurising bore, a transverse wall is provided therein to close off the lower end i portion below the outlet. A similar wall can be provided in the lifting bore, below its inlet.

In an installation according to the invention, the t t t head of the or each pressurising bore is connected to a source S o f pressurised water, such as a high pressure pump at ground level. Additionally, the air supply means of the or each lift bore is connected to a source of pressurised air, such as an air compressor at ground level. The respective supply of pressurised water to the pressurising bore, and compressed air Scc to the lift bore air supply means is commenced, with the supply of pressurised water preferably being establisned a short time in advance of the supply of air. High pressure water discharge from outlet of the pressurising bore causes material of the deposit to be mined to be moved towards and into the inlet of the lift bore. The high pressure water, as well as the water pressure naturally prevailing in the deposit, is sufficient to generate in the lift bore a substantial column of material and water extending above the level of air discharge in the lift bore from its air supply means. The pressurised air discharge causes aeration creating a substantial air-lifting force in the column, sufficient to 1 raise it at high velocity to above ground level, thereby generating a strong pumping action which augments the action of the pressurised water by drawing material from the deposit into and up the lift bore.

At ground level, the material raised to above that level is passed to a gold recovery plant, after at least a proportion of its water content has been removed if required and charged to a clean water dam from which it can be drawn for further use. The recovery plant can be of conventional form appropriate to the alluvial nature of the deposit, typically including for example a sluice box with DSM screen and amalgamating plates. The material raised to above ground level preferably passes to the recovery plant by utilizing the kinetic energy imparted thereto by the air-lift action, *',othereby minimising pumping requirements for the plant.

the A proportion of the sand and gravel separated from the raised material can be stock-piled for sale, given its S 01o 0o. nature and suitability for use in various applications.

*#***'However, a major proportion, and environmentally acceptable tailings from gold recovery operations, can be returned to the below ground deposit, such as into a previously worked area.

9t Thus, the installation may include a recycle bore through S which such sand, gravel and tailings are discharged into the V deposit under the pressure of water with which it is pumped S into the recycle bore.

Periodically, the mining operation will be interrupted by boulders obstructing the inlet to the lift bore. The installation therefore preferably has means for removing the obstruction, to permit the operation to continue.

In one arrangement, the lift bore is of a form enabling its inlet to be cleared of obstructing boulders. In that form, the lift bore may be longitudinally divided to define a lift bore portion and an auxilliary portion. The lift bore portion is arranged and as previously described.

The auxilliary portion is connected to a source of pressurised water and, at least to one side of the inlet to the lift bore portion, is provided with high pressure water jets.

Preferably such jets are provided at each side of, and below, the inlet, and are oriented such that pressurised water -7i; issuing therefrom impinges on boulders obstructing the inlet.

Preferably, the supply of pressurised water to the pressurising bore is terminated during operation of the water jets so as not to generate pressure impeding the clearing or cutting action of the jets.

Alternatively, an obstruction can be cleared by a backwashing operation. For this, the supply of pressurised water normally discharged into the deposit through the pressurising bore is switched so as to discharge through the lift bore. As will be appreciated, this more simple arrangement merely necessitates a suitable multi-port valve at the mine site at ground level enabling the supply of pressurised water to be switched between the pressurising and lift bores.

In further alternatives, the installation may be adapted for the use of a percussion cable drill or a "down the hole" hammer drill. Such devices can be used in the manner known in the art, by operating down through the lift bore.

However, their use is not preferred where pressurised air is

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supplied to that bore by air supply means comprising a conduit S extending within the lift bore, due to the likelihood of damage to such conduit.

In a still further alternative, the casing and pipe column of the lift bore may be rotatable. In the event that S its inlet is obstructed, it may be simply rotated to a new orientation, or rotated to effect clearance and then returned to its initial orientation, before recommencing the mining operation.

If it is found that obstruction of the inlet to the lift bore is a frequent occurrence, there may be no alternative to enlarging the diameter of the lift bore and installing a corresponding larger diameter casing with a larger inlet.

Deep lead gold bearing deposits, such as those occurring in Victoria, can extend for several kilometres, while they also can be of substantial width. However, in many instances, they are quite narrow and enable a mining installation according to the invention to operate across the full width. Particularly given the shallowness of the FY -8- I-lli~L deposits, a particular mine site can be worked out in a relatively short interval of time, necessitating relocation of the mine site further along the deposit. In one form, the mining installation therefore is mobile to a substantial degree, enabling the mine site to be moved at intervals along the deposit.

Thus, the installation may include a mobile bore hole drilling rig, operable in advance of the mine site to prepare successive bore holes, while the gold recovery plant also may be mobile. In one mode of operation with such mobile installation, pressurising and lift bores in a first stage of operation may have their function changed for use in a second stage. Thus, the pressurising bore for the first stage can be Sused as a return bore in the second stage, with the lift bore of the first stage being used as the pressurising bore for the second stage after being turned to orientate its outlet toward a new bore to function as the lift bore of the second stage.

The mobile drilling rig can be used to drill successive bore holes enabling this procedure to be repeated, as required, with the mobile recovery plant being moved as required.

Obviously, the casing of successive bore holes can be S recovered for re-use in subsequent stages when their use in a preceding stage has been completed.

Reference now is directed to the accompanying S drawings, in which: Figure 1 is a schematic sectional view of a mine site showing a mining installation; Figure 2 shows on an enlarged scale installation bores of an installation as in Figure 1; Figure 3 shows a section of a lift bore for one embodiment of the invention; Figure 4 shows an alternative lift bore of a second embodiment of the invention; Figure 5 shows a sectional view of a still further form of lift bore; Figure 6 shows the overall form of the lift bore of Figure Figure 7 shows a sectional view of exploratory bores in an unworked deep lead, and i 1- Figures 8 and 9 show in section and plan view, respectively, one layout of installation bores for use of the present invention.

In Figure 1, the water saturated gold bearing sand and gravel wash comprising a deposit 10 from which material is to be extracted is shown as extending over an impervious bed rock 12, with there typically being a thin layer 14 of clay therebetween. Over the deposit, there is an overburden of basalt 16, recent gravels 18 and surface soil 20. The section is not to scale; a number of such deposits typically being of a thickness of the order of up to about 10 metres and at a basement depth of up to about 150 metres.

For extraction of material from the deposit, the mining installation is shown as comprising a number of bore holes, of which bores 22, 24 and 26 are in use in an 4 extraction stage. The mobile drill 28 used to drill the holes Sfor bores 22, 24 and 26 is shown as having moved just beyond o the immediate mine site, and to be drilling a hole 30 for a successive stage.

0 0 Holes 22, 24 and 26 have respective casings provided by pipe strings 32,34 and 36; pipes 32 and 34 respectively comprising pressurising and lift bores. A high pressure water pump 38 is shown as connected to the head of pipe 32, while a compressor 40 driven by the motor of the drill rig 28 is connected to air supply means of pipe 34.

As shown in Figure 2, pipes 32 and 34 have lower end portions which extend into the bed or basement rock 12.

SAdjacent the interface of that rock and deposit 10, pipe 32 r has an outlet 42 facing toward pipe 34, while pipe 34 has an inlet 44 facing toward pipe 32. High pressure water, shown by arrows A, supplied to pipe 32 discharges from outlet 42 into the deposit 10 and causes the free-running material of deposit to move toward inlet 44 of pipe 34.

Over the portion of its length from just above ground level to a short distance above its inlet 44, pipe 34 is of double wall construction, with air from the compressor passing to the annular cavity 46 between those walls. The pressurised air passes down cavity 46 as shown by arrows B, and issues from a manifold defined at te lower end of the .i ri Ir- c i.

double wall so as to enter the interior 48 of the inner one of the walls of pipe 34. The pressurised air then provides an air-lift action on a column of water and material from deposit established by the pressure generated by water discharged from pipe 32 and the prevailing ground water pressure in the deposit. As a consequence, the column of water and material is aerated and raised in pipe 34 as shown by arrows C, at a substantial velocity, due to the air lift action generating substantial pumping which operates in concert with pressurised water from pipe 32.

The head 50 of pipe 34 preferably is curved or of goose-neck form, to control the discharge of material therefrom at ground level. Also, at that level, pipe 34 may S have a power operated, swivel portion 52,. enabling its inlet 44 to be oriented as required by rotating pipe 34 bodily in its bore hole 24.

Material discharged at ground level from pipe 34 is 0* io. passed to a gold recovery plant 54 as previously described, preferably after any necessary de-watering and separation of coarse gravel and boulders. At the mine site at ground level, M and N in Figure 1 respectively designate stockpiles of sand t and gravel and settling dams.

Figure 3 shows an alternative form of Pipe 34. As shown, the pipe 34 comprises a pipe string provided by successive pipe sections 56, with adjacent pipe ends coupled together by means known in the art. .The same preferably applies to pipe 32.

In the arrangement of Figure 3, the air supply means Sis provided by at least one air-line or conduit 60 which extends down through pipe 34. At its upper end, conduit 60 is connected to air compressor 40, from which it receives pressurised air to be discharged within pipe 34, above its inlet 44, to generate the required air-lift action. Conduit may comprise successive lengths 62, each located by at least one bracket 64 in a respective pipe section 56 of pipe 34, with successive conduit lengths 62 connected together by a screw coupling 66. When a further section 56 of pipe 34 is inserted in drilled hole 24 and connected to a preceding section 56, its conduit length 62 is rotated in its bracket(s) -11ii 64 to connect to the conduit length 62 of the preceding pipe section 56. The new conduit length 62 then is fixed against rotation in its bracket(s) 64, enabling a further similar connection.

Figure 4 shows in further detail a further form of pipe 34 for which the air supply means is provided by that pipe being of double wall construction. In this instance, pipe 34 may be installed by successive sections of the inner and outer walls 67,68 being screw threaded to respective such sections. However, the lowest level of the double wall arrangement has the inner and outer walls 67,68 sealed together, such as by a circumferential weld 69 therebetween.

That seal is located a relatively short distance above the inlet 44 of pipe 34. Also, a single port 70 or a circumferential array of ports, provided in the inner wall 67, .just above seal 69, enables compressed air to be discharged o" into the interior of inner wall 67 to provide the required air-lift action.

Figures 5 and 6 show a form of pipe 34 adapted for clearance of an obstruction to its inlet 44. Pipe 34 has inner and outer pipes 71,72 eccentricly arranged, with inner pipe 71 defining what functionally is to serve as the air-lift Sbore 73. Thus, the inner pipe defines an opening which is to provide inlet 44 and through which is received water and t tz Smaterial from the deposit which is to be raised to ground level. The outer pipe has a similar opening which extends around that of the inner pipe, with the spacing between two penings being closed by a baffle 74 around the periphery of ,e the inner pipe opening. High pressure water charged to the passage 76 between the inner and outer pipes is able to discharge horizontally through high pressure water nozzles 78 in baffle 74 which generate jets D to impinge on, and move, or cut, boulders obstructing the inlet 44.

Below the inlet to the inner pipe, the pipes are closed off by a transverse upper and lower walls 79,80. Water from the passage between the pipe walls is able to pass through an opening 81 in the upper transverse wall 79, and discharges vertically upwards through a further water nozzle 82 in upper wall 79 to generate jet E to further impinge on

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-12i;I boulders obstructing inlet 44.

The air supply means in the arrangement of Figures and 6 comprises an air supply conduit 62 extending within passage 76 between the inner and outer pipes and which, at its lower end, communicates with the interior of the inner pipe to discharge compressed air for the required air lift action.

That communication may be via a single inlet port 70 in the inner pipe, or via a circumferential array of ports defined by a manifold extending around the inner pipe and with which the conduit communicates.

Operation of the high pressure water jets is as previously described. The jets may, if required, be pressure responsive and operable only when pressure generated in the passage between the inner and outer pipes exceeds a predetermined level.

o AV With reference to Figures 7 to 9, operation of the mining method of the invention in a state of production may be best described by an example of its application to a typical deposit as follows:- A deposit of free-running gold-bearing gravel 84 has been discovered beneath 30 metres of overburden 86 as shown by Figure 7. This deposit extends below the overburden for 24 metres to basement rock and is totally water saturated. From the results of drilling a series of 170 mm diameter exploratory holes H at 112 metre intervals and carrying out test work it is ascertained that few boulders or large pebbles will be encountered on the basement, or in the gravels generally, which will be too large to pass through a 150 mm diameter pipe.

Using the deepest exploratory hole H as a grid line intersection point, a survey grid is l.aid out at 3 metre line spacings and bore hole positions numbered 88 to 101 inclusive are selected as shown by Figure 9, to cover a 12 metre by 12 metre square for pressurising bores. Finally a 324 mm diameter hole H' to house a pipe arrangement as shown by Figure 6, is (rilled in the centre of the pattern to be the lift bore for mining out the 12 metre x 12 metre square area.

The remaining holes are drilled 170 mm in diameter to completion depth at about 1 metre or more into basement rock.

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Hole spacings and diameters are determined by production and mineability characteristics for a given deposit and may be varied to suit a particular set of circumstances.

In this case it has been determined that the hole spacings of 3 metres will be suitable for a mining rate of 100 bank cubic metres per hour and that a discharge pipe of 150 mm diameter will be large enough for the desired production rate.

The total amount of mineable gold-bearing gravel within the 12 metre x 12 metre pattern is 3,500 bank cubic metres and working a 10-hour shift daily for a 5-day week and allowing for 30% of unproductive time, the mining and treating of 3,500 b.c.m. at an 80% recovery, and for a price of $A600 per ounce for gold, the total value of the gold recovered would be $A216,000, or over $A10,000,000 per annum. Although this may be an exaggerated theoretical example, it serves to illustrate the magnitude of the scope which may exist for the development of a profitable enterprise.

With the advent of favourable results from the t.t. mining method and from exploratory work, a number of mining operations may be established and ancillary techniques may be improved with experience to enhance the efficiency and versatility of the mining method. Teething troubles must be anticipated and, whilst pipe obstructions may be a major cause, "hang-ups" must also be expected and these may be overcome by the use of explosives or high pressure water jets. When a loss oc production occurs due to a "hang-up" of the material being mined, or the face of that material is no S longer within the range of the hydraulicking water from the pressurising bore, the high pressure water bore can be transferred to the next bore hole of the mining sequence.

Following this the casing of the hole vacated may be lifted a calculated distance and an explosive charge placed at a suitable depth to overcome the "hang-up" as shown in Figure 8. Alternatively, high pressure water jets may be used in the vacated hole to free the "hang-up". There will be a proporation of the tailings from the gold recovery plant which cannot be returned underground as fill and this may be stockpiled and sold as gravel and sand products. Following a successful outcome from field test-work, costing and FY -14- 1 ~r i p -a Ln profitability exercised can be prepared to determine the viability of the mining method in a given deposit.

While the invention has been described primarily with emphasis on water saturated gold bearing deep lead wash deposits, it will be appreciated that the invention readily will be applicable to similar free-running deposits of other minerals. With the addition of ancilliary equipment and techniques, it is possible also to apply the invention to deposits which are not free-running but may be made so. It will be appreciated that the invention is well suited to remote-control operation at ground level, and enables low cost, high volume mining; while, with such free-running deposits, comminution of the mined material is not necessary either below or at ground level.

**In use, the invention is not seriously impeded by large boulders in the deposit, as these can be moved when causing an obstruction as described herein. Also, large *tt boulders generally are present at, or move to basement level, ,4 and the inlet to the lift bore can be positioned slightly above that level, if required. Also, once the configuration of a deep lead deposit has been delineated and a knowledge S gained of the nature of occurrence and sizing characteristics S of the material of the deposit, the most suitable diameter lift bore casing diameter and inlet size can be chosen to S minimise loss of production caused by obstructions. Loss of production also can be reduced by provision of standby pressurising or lift bores able to be brought into operation when required.

The development of a successful mining operation according to the invention, remotely controlled from the surface through bore-holes, has the following desirable features:- 1. A small plant and equipment requirement.

2. The plant is able to be portable and/or mobile.

3. A relatively low capital requirement.

4. Minimum risk factor.

Early cash flow.

6. Short time lag between a decision to proceed with field test work and the achievement of a state of production if the test work is favourable.

7. Field productivity tests may be conducted on a large scale at relatively low cost in a short space of time. A suitable system of drilling can be used for drilling most of the bore-holes, in particular where large diameter production holes of say up to 1500 mm diameter and depths of up to 150 metres or over are warranted.

8. Neither the exploratory or operational work need have any harmful inpact on the environment, nor need the quality of the ground water or the water table be effected.

A cyanide plant may be required to treat and recover gold from finely sized material derived from the tailings of .*to the primary recovery plant. However, this can be operated ,substantially without risk of environmental hazard by conventional procedures.

tFinally, it is to be understood that various StttJt alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambi+ of the invention.

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Claims (19)

1. A mining installation for recovery of minerals from a below ground deposit, the installation including at least two bore holes which are mutually spaced and extend into the deposit, said bore holes including: at least one bore hole (herein referred to as pressurising bore) connectable to a source of pressurising liquid and having an outlet within the deposit, and at least one further bore hole (herein referred to as a lift bore) having an inlet thereto within the deposit, said lift bore having means for discharging pressurised gas therein; the arrangement being such that pressurised liquid supplied to the pressurising bore is able to discharge from said outlet to cause solid material of the deposit to move toward the lift bore under hydraulicking action of the liquid, with the means for discharging pressurised gas in said lift bore being operable to provide an air-lift action on the solid 20 material moved towards the lift bore such that the solid material is raised in the lift bore.

2. An installation according to claim 1, wherein each of said bore holes are provided with a respective casing, the casing of the pressurizing bore defining the outlet thereof and the casing of the life bore defining the inlet thereof.

3. An installation according to claim 2, wherein the casing of each of said bore holes is in the form of a respective steel or polyethylene pipe column.

4. An installation according to any one of claims 1 to 3, 30 wherein the pressurised liquid is provided by pressurising means connected to an upper end portion of the pressurising bore, the pressurising means providing liquid at a pressure such that said hydraulicking action and air-lift action are operable in concert in to raise a column of liquid in the lift bore, and thereby generate a pumping force operable to raise the solid material from said deposit through said lift bore to ground level. An installation according to any one of claims 1 to 4, AL 1 herein said air supply means discharges air in lift bore a ort distance, such as from 750 to 2000 mm, above the inlet Z -17- j '2 1 1fi 444k 4 *ir ~II~Y LILCI-- to the lift bore.

6. An installation according to any one of claims 1 to wherein said lift bore has a double wall construction over at least a major part of the height thereof, the air supply means including a passage between inner and outer walls of said construction and an air discharge port means providing communicating between said passage and the interior of the inner wall and enabling discharge of pressurised air within said lift bore.

7. An installation according to any one of claims 1 to wherein said air supply means includes at least one conduit extending longitudinally of, preferably within, the at least one lift bore, the at least one conduit terminating at its S lower end at discharge port means from which pressurised air is able to be discharged within said lift bore. S 8. An installation according to any one of claims 1 to 7, wherein said lift bore is provided at its upper end with a curved or angled portion by which the pressurised liquid and material from said deposit can be discharged into a receiving area or facility.

9. An installation according to any one of claims 1 to 8, wherein the outlet and inlet respectively of the pressurising bore and the lift bore is able to be raised progressively during a mining operation. An installation according to any one of claims 1 to 9, wherein the lift bore is provided adjacent its inlet with means for discharging, outwardly and/or across the inlet, high pressure water jets operable to clear an obstruction from the inlet.

11. An installation according to any one of claims 1 to wherein said lift bore is connectable to a source of high pressure liquid by which back washing of liquid discharged through said inlet can be used for clearing an obstruction to said lift bore.

12. An installation according to any one of claims 1 to 11, wherein there is a plurality of pressurising bores disposed around a single lift bore.

13. A method for the recovery of minerals from a below ground deposit, wheren the method comprises installing at -18- least two matually spaced bore holes which extend into the deposit, said bore holes including: at least one bore hole (herein referred to as pressuring bore) connected to a source of pressurising liquid and having an outlet within the deposit, and at least one further bore hole (herein referred to as a lift bore) having an inlet thereto within the deposit, said lift bore having means for discharging pressurised gas therein; and wherein pressurised liquid is supplied to the pressurising bore from said source so as to discharge from said outlet and cause solid material of the deposit to move toward the lift bore under hydraulicking action of the liquid, with pressurised gas from said supply means being discharged in said lift bore to provide an air-lift action on the solid material moved towards the lift bore and thereby raise the material in the lift bore. bore holes are provided with a respective casing, such that the casing of the pressurizing bore defines the outlet thereof and the casing of the lift bore defines the inlet thereof. The method according to claim 14, wherein the casing of each of said bore holes is provided in the form of a SI respective steel or polyethylene pipe column. S 16. The method according to any one of claims 13 to wherein the pressurised liquid is provided by pressurising t means connected to an upper end portion of the pressurising bore, the pressurising means being operated to provide liquid at a pressure such that said hydraulicking action and air-lift action are operable in concert in to raise a column S, of liquid in the lift bore and thereby generate a pumping force operable to raise the solid material from said deposit through said lift bore to ground level.

17. The method according to any one of claims 13 to 16, wherein said air supply means is arranged to discharge air in lift bore a short distance, such as from 750 to 2000 mm, above the inlet to the lift bore. -19- I

18. The method according to any one of claims 13 to 17, wherein said lift bore is provided with a double wall construction over at least a major part of the height thereof, the air supply means including a passage between inner and outer walls of said construction and an air discharge port means providing communicating between said passage and the interior of the inner wall and enabling discharge of pressurised air within said lift bore.

19. The method according to any one of claims 13 to 17, wherein said air supply means includes at least one conduit extending longitudinally of, preferably within, the at least one lift bore, the at least one conduit being provided at its L lower end with discharge port means from which pressurised air is discharged within said lift bore.

20. The method according to any one of claims 13 to 19, i wherein said lift bore is provided at its upper end with a curved or angled portion by which the pressurised liquid and :C ,,,material from said deposit is caused to discharge into a receiving area or facility.

21. The method according to any one of claims 13 to wherein the outlet and inlet respectively of the pressurising bore and the lift bore is raised progressively during a mining operation.

22. The method according to any one of claims 13 to 21, wherein the lift bore is, provided adjacent its inlet with means for discharging high pressure water jets outwardly and/or across the inlet, said discharge means being operated periodically as required to clear an obstruction from the Sinlet.

23. The method according to any one of claims 13 to 22, wherein high pressure liquid periodically, as required, is charged to the lift bore to cause back washing by liquid discharged through said inlet can be used for clearing an obstruction to said lift bore.

24. The method according to any one of claims 12 to 22, wherein a plurality of pressurising bores is disposed around a single lift bore. The installation according to claim 1, substantially as herein described with reference to any one of the L embodiments of the accompanying drawings.

26. The method according to claim 13, substantially as herein described with reference to any one of the embodiments of the accompanying drawings. DATED: 26 May 1988 PHILLIPS ORMONDE FITZPATRICK Attorneys for: LAWRENCE REGINALD BASTER t t I t I s ft tr -21-