GB2196673A

GB2196673A - Mining method and apparatus

Info

Publication number: GB2196673A
Application number: GB08725284A
Authority: GB
Inventors: Gerald Richard Oldham Pentith
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-10-28
Filing date: 1987-10-28
Publication date: 1988-05-05
Anticipated expiration: 2007-10-28
Also published as: GB2196673B; GB8725284D0; GB8625782D0

Abstract

Method and apparatus for long wall mining are described in which a series of slots (12, 14) are cut into a face (10) at suitable angles, the slots (12, 14) intersecting to define a block (16). Portions are progressively separated from the block (16) e.g. by an impact hammer (38) which follows the cutters (32, 34). Conveniently at least one pair of inclined slots (12, 14) are produced simultaneously by using a pair of appropriately positioned cutters (32, 34), one of which follows immediately after the first so that the first and second slots (12, 14) are cut substantially simultaneously. The cutters are rotary diamond saws and the method allows mining of very hard material, for example gold bearing rocks, without the necessity to use blasting techniques. <IMAGE>

Description

SPECIFICATION Mining method and apparatus This invention is concerned with methods and apparatus for mining and especially for socalled long wall mining.

In mining of hard rock, for example mining from gold bearing reefs, there has so far been little mechanisation due partly to the natural conditions encountered including the extreme hardness of material being mined and difficulty of handling the environmental conditions at the enormous depths at which gold mining is commonly carried out. It is desirable to devise a method of mining such hard materials without the usual drilling and blasting operations which have commonly been used until now.

Other methods have been proposed but none has been altogether satisfactory because of an inability to provide reliable bulk output under the demanding conditions, especially of severe roof pressures normally ;encountered in deep mines.

According to the invention, in one aspect, a method of mining material from a face is proposed which comprises cutting first and second slots in the face inclined at acute angles to it and arranged to intersect one another progressively in a generally horizontal direction along the face whereby to form a block of material extending generally horizontally along the face, and separating portions from the block.

Preferably in a method in accordance with the invention two headers are first formed by excavating a pair of spaced tunnels to predetermined positions and excavating a transverse header to connect the tunnels thereby providing an initial face (along one wall of the transverse header). The headers are arranged to extend at least a little beyond the transverse header to form a chamber from which the slots are cut into and along the face. The two headers are excavated further as the mining progresses to provide the chamber from which the slots are cut and in which cutting means may be manipulated. Alternatively, of course, the two headers may be cut to their full desired lengths initially.

In a preferred method as set out in the last preceding paragraph, of long wall mining, the first slot is cut and the second slot is cut immediately following the first slot so that the first and second slots are progressively cut along the face substantially together: the second slot trails the first slot by a small amount.

In this preferred method the portions of material are separated from the block progressively after the second slot is cut, following along the face closely after the cutting of the slots. In this method a pair of intersecting slots is cut substantially simultaneously along the whole length of the face and the portions of the block cut are separated as the cut progresses along the face from one end to the other. Having traversed the whole length of the face, a further pair of cuts can readily be made to remove a further parallel block of material by traversing the cuts back along the face in the opposite direction to the first cuts.

In this way, by a series of cuts along the face, the material is removed and the face thus cut back progressively.

In an alternative method embodying the invention a plurality of parallel first slots are cut simultaneously and a plurality of spaced parallel second slots each intersecting an associated one of the first slots are likewise cut simultaneously to form a series of parallel blocks of material, the cuts forming the second slots trailing the cuts forming the first slots along the face.

In another aspect the invention may be considered to provide apparatus for use in mining material from a face comprising cutting means for cutting first and second slots in the face inclined at acute angles to the face and arranged to intersect one another, means for moving the cutting means progressively in a generally horizontal direction along the face to cut the slots whereby to form a block of material extending generally horizontally along the face, and means for separating portions from the block.

Preferred apparatus in accordance with the invention comprises a conveyor, suitably extending parallel to the face, on which the cutting means is mounted which provides said means for moving the cutting means in a generally horizontal direction. Conveniently the conveyor, as well as mounting the cutting means, comprises means for removing the separated portions of the block.

In preferred apparatus in accordance with the invention the cutting means comprises diamond saws, preferably rotary diamond saws.

In a preferred apparatus, a bank of saws cuts the slots from one end of the face to the other and is mounted on a so-called armoured flexible conveyor of well known construction which carries away the portions of material released by the cutting action of the diamond saws.

A preferred method embodying the invention involves the creation of a so-called long wall retreat face. This is created by driving two (usually parallel) headings, which ultimately provide a so-called main gate and tail gate, to a predetermined position at which they are inter-connected by a further heading.

This heading is then equipped with an appropriate conveyor on which cutting means is mounted (as hereinbefore described) for carrying out the method. One suitable conveyor is known as an armoured flexible conveyor and is of generally known construction. The principal of mining using a long wall retreat face is likewise well known, in the coal mining industry for example.

In this type of mining, appropriate powered supports are used to support the roof of the excavation as it moves forward cut by cut as material is mined from the face. Behind the apparatus, the roof may be allowed to collapse and access to the working face is gained by means of the main gate and/or tail gate headings.

Referring to the accompanying drawings: Figure 1 is a diagrammatic side view showing one method embodying the invention; Figure 2 is a further diamgrammatic side view showing a second method embodying the invention; Figure 3 is a perspective view of a severed block indicating the point at which a portion of the block may be separated; Figures 4 to 6 are side views showing various stages in carrying out the method shown in Figure 2; Figure 7 is a diagrammatic view of apparatus embodying the invention for carrying out a method embodying the invention; Figure 8 is a front view of a further apparatus which may be used in carrying out the invention; Figure 9 is a view of part of the apparatus shown in Figure 8; and Figure 10 is a plan view showing headers and face.

In Figure 1 is illustrated a method embodying the invention in which material is mined from a face 10 by cutting first and second slots 12, 14 in the face 10, the slots 12, 14 being inclined at acute angles to the face and arranged to intersect one another, The slots 12, 14 are cut progressively in a generally horizontal direction along the face 10, to form a block of material 16 (see also Figure 3) which extends generally horizontally along the face 10. In further carrying out this first method embodying the invention portions 18 are separated from the block by any convenient means. In Figure 3 the portion 18 is shown as being separated by a impact hammer which hits the block 16 at a region indicated by the reference 20.

In a preferred method in accordance with the invention, the blocks are separated by a suitable pneumatic or hydraulic impact hammer. However, the portions may be separated from the block by any suitable means, for example by providing a third cut intersecting both the second and first cuts, conveniently in a vertical direction, whereby to separate the portion of the block.

In carrying out the first method embodying the invention described, the block 16 is removed and two holes 22 are bored in the face 10 above and below the part from which the block 16 has been removed, and the remainder of the material being blown from the face by suitable explosive charges placed in the holes 22. However, because this first method involves the use of explosives which is preferably avoided, the first method is not preferred.

In a second method embodying the invention shown diagrammatically in Figure 2, a plurality of intersecting cuts are made in a face 10, a first series of spaced parallel slots 12 being cut at an acute angle to face 10 and a second spaced parallel set of slots 14 being cut at a different angle to the face 10 to intersect the first slots, each of the second slots 14 intersecting an associated one of the first slots 12. In Figure 2 two of the sets of first and second slots are shown. It will be seen that at the top and bottom of the working, slots 26 are cut which are generally perpendicular to the face 10 at the top and bottom of the face to define the floor 28 and roof 30 of the working.

In one method of mining by cutting a pattern of slots substantially as shown in Figure 2, apparatus in accordance with the invention iS used comprising cutting means 37 including first and second rotary diamond saw cutters 32, 34 mounted on a carriage 36 (see Figure 7).

As can be seen from Figure 4 the two cutters are inclined at an acute angle to the face 10 and the slots 12, 14 cut by them are arranged to intersect. As can be seen from Figure 7, the cutters 32, 34 are offset from one another longitudinally of the face 10 so that there is no clash when cutting the slots.

An impact hammer 38 is arranged to follow the cutters as they progress along the face 10 in the direction indicated by the arrow A (Figure 7) and separate portions of blocks 16 of material cut by the cutters 32, 34 from the face in a manner generally similar to that described with reference to Figure 3.

In carrying out the second method, using the apparatus referred to, the cutters 32, 34 are first used to remove a substantially central block 16 disposed roughly midway between the roof 30 and floor 28 of the working and then to successively removed in successive passes along the face other blocks 16 in a second operation and a third operation. The cutters 32, are arranged to be adjustable in angle of cut so that for a fourth operation, the cutters 32 can be arranged to cut a slot which provides the continuation of the roof 30 and in the fifth operation, the cutters 34 can be adjusted to cut a slot which provides substantially a continuation of the floor 28. Depending on the height of the face a greater or lesser number of operations may be required and a greater or lesser number of blocks 16 cut.

In a third illustrative method, a plurality of parallel slots may be cut simultaneously by an appropriately mounted bank of cutters. In Figures 8 and 9 one suitable apparatus is shown for effecting such an operation comprising cutting means 37 having two parallel cutters 34.

Any desired number of parallel cutters may be provided to provide spaced parallel cuts and a further set of parallel cutters (not shown) inclined to the first set may be provided to make the second slots. Alternatively, the angle of.the first set may be adjusted to make the second parallel slots following completion of the first parallel slots, by a subsequent movement along the face 10.

As hereinbefore mentioned, the operation is started by first making headings 40, 42 referred to as the main gates 40 and the tail gates 42 respectively and interconnecting these by a further heading providing the face 10; the initial headings 40, 42 are continued a little beyond the face 10 to provide a so cailed "stable" into which the cutters can be positioned to make the cuts along the face 10.

Conveniently the cutters are inclined at an angle ;'X" of about 60 to 700 to the face 10 as shown in Figure 4. Headings are extended as necessary to facilitate the cutting operations from an open end face into the main long wall face 10.

The intervals between each of the parallel cuts is selected as required so that when the material is released by separating the portions from the block, it is of such a size that it can be readily cleared by conveyor means without lumps becoming caught and causing blockages.

As previously mentioned, the portions may be broken off the block defined by the slots 12, 14 by convenient means suitably impact hammers or other progressive tools hydraulically, pneumatically or electrically powered.

Impact devices are able to break off the portions of previously cut material, for example gold bearing rock, using relatively little power.

The impact point of the tools is conveniently positioned so that the portions of material separated are limited in length so that the conveyor clearing system can readily deal with them.

The headings 40, 42 may be excavated by suitable heading machines using, conveniently, diamond saw cutting elements.

As the cutting of the face 10 continues the face retreats from the initially formed transverse heading 44; a working space is supported by support means (not shown) in known manner and beyond the region of the support means behind the cutting apparatus, the roof of the excavation may be allowed to collapse, or may be packed, as desired.

The apparatus in accordance with the invention, both as shown diagrammatically in Figure 7 and Figures 8 and 9, conveniently comprises a conveyor system of the type commonly known as an armoured flexible conveyor 50 (Figure 9). In this type of system, a series of heavy duty steel trays, commonly referred to as pans, are loosely connected together and. the pans are connected at one end to a drive unit adjacent the junction of the face 10 and main gate 40 and the other end to a return unit at the junction of the face 10 and the tail gate 42. Means is provided to transport the mined material along the line of pans to the drive unit end at which it is delivered to a secondary conveyor, such means commonly comprising spaced bars which are moved along the line of pans by a suitable chain assembly. Suitable rams are provided to push the conveyor 50 forward as the face 10 advances.The cutting means is conveniently mounted on the line of pans of the armoured flexible conveyor by known means which, in effect, provides a type of rail system and is able to haul itself along the line of pans by a suitable drive system of known construction, for example operating on a rack and pinion principle and cooperating with a chain. Mounting of the cutting means 37 on the armoured flexible conveyor provides a stable base from which the cutters 32, 34 can work and also provides the basis of a conveyor system for removing the mined material.

As an alternative to the scraper bar system, an oscillating push mechanism may be mounted on the pans of the conveyor 50, operated from either end with push guides at the rear of the pans and being provided with cantilevered flights to impel the portions of the blocks which are separated, towards the loader gate for delivery onto the secondary conveyor. As hereinbefore mentioned a suitable support system is also provided for supporting the roof adjacent the face 10. The main gate 40 and tail gate 42 provide the main access to the working space adjacent the face 10 and are reinforced along their whole length in the usual way.

In trials, speeds of cutting of 0.75 metres to 1.0 metres per minute in 20,000 Ibs per square inch limestone making a slot about 1.6 cms wide and about 46 cms deep were achieved. it is expected that by suitable selection of diamond cutters, speeds considerably in excess of this will be obtained and these may be further enhanced by use of other aids, for example pressure water jetting.

Where a single cutting disc or pair of discs is to be used, as well as it being necessary to adjust the cutting angle of the discs to provide appropriate angles of attack, the height of the discs must also be adjustable to cut the blocks at the various heights up the coal face. Furthermore, where the cutters are to traverse along the face from either end, separator units, for example impact hammers are preferably provided at both ends of the cutter, the hammer trailing the direction of movement of the cutter means being used to separate portions from the block in operation. The face 10 to be excavated may be of any convenient height for example about 1.5 metres and may be of any suitable length. It is important to cut the blocks and remove the material as quickly as possible so that the new supports can be introduced before any substantial closure of the working space occurs.The face 10 may be of any suitable length and it is not uncommon for a face of 100 or more metres to be contemplated in long wall mining methods.

By using the methods and apparatus described, material can be mined, for example gold bearing rock, without the dangers associated with current practises of drilling holes and blasting material from the solid face with explosives. The method described herein requires little skilled operator control as the cutting apparatus traverses the mineral face and the method can be carried out remotely if required.

The mining environment becomes much safer and tolerable to the labour employed.

The use of an armoured flexible conveyor simplifies the method of mining and support of the workings because they do not have to withstand projectiles caused by the current practise of blasting the rock.

By this means, the operation of producing ores from very hard rock materials can be made much safer and may be substantially cheapened.

Claims

1. A method of mining material from a face comprising cutting first and second slots in the face inclined at acute angles to the face and arranged to intersect one another, progressively in a generally horizontal direction along the face whereby to form a block of material extending generally horizontally along the face and separating portions from the block.

2. A method according to Claim 1 wherein the first slot is cut along the length of the face and thereafter the second slot is cut.

3. A method according to Claim 1 wherein the first slot is cut and the second slot is cut immediately following the first so that the first and second slots are progressively cut along the face substantially together.

4. A method according to any one of the preceding claims wherein the portions are progressively separated from the block after the second slot is cut following along the face closely after the cutting of the slots.

5. A method according to any one of the preceding claims wherein the portions are separated by breaking them off.

6. A method according to Claim 5 wherein the portions are broken off using an impact hammer.

7. A method according to any one of the preceding claims wherein the portions are separated by cutting a third slot intersecting the first and second slots.

8. A method according to any one of the preceding claims wherein a plurality of spaced, parallel first slots are cut simultaneously and a plurality of spaced, parallel second slots each intersecting an associated one of the first slots are cut simultaneously to form a series of parallel blocks of material.

9. A method according to Claim 8 wherein the portions are separated from the blocks simultaneously.

10. A method according to Claim 9 wherein the portions are separated at staggered positions along the face.

11. A method according to Claim 10 wherein the position of separation of the portions from a block trails that of the adjacent block below.

12. A method according to any one of the preceding claims wherein uppermost and lowermost slots are cut aligned with the top and bottom of the face respectively.

13. Apparatus for use in mining material from a face comprising cutting means for cutting first and second slots in the face inclined at acute angles to the face and arranged to intersect one another, means for moving the cutting means progressively in a generally horizontal direction along the face to cut the slots whereby to form a block of material extending generally horizontally along the face, and means for separating portions from the block.

14. Apparatus according to Claim 13 comprising a conveyor on which the cutting means is mounted.

15. Apparatus according to Claim 14 comprising a conveyor clearance system by which separated portions re removed from the face.

16. Apparatus according to either one of Claims 14 to 15 wherein the conveyor comprises a rail system on which the cutting means is mounted.

17. Apparatus according to Claim 16 comprising an oscillating conveyor push mechanism mounted on the rail system.

18. Apparatus according to Claim 17 comprising cantilevers arranged to impel separated portions to a loaded gate for delivery to a secondary conveyor.

19. A method of mining substantially as hereinbefore described with reference to Figures 4, 5 and 6.

20. A method of mining substantially as hereinbefore described with reference to Figures 8 and 9.

21. Apparatus for mining constructed arranged and adapted to operate substantially as hereinbefore described with reference to Figure 7.

22. Apparatus for mining constructed arranged and adapted to operate substantially as hereinbefore described with reference to Figures 8 and 9.