Method and apparatus for mining coal or other solids in flooded mines

[57] ABSTRACT

A mining method utilizes deliberately flooded subterranean mines, and additionally employs completely submersible remotely controlled mobile mining machinery. The surrounding flood water in the mine is used as the transporting medium for a slurry of mined material as the latter is conveyed to the surface through a system of pipes and booster pumps.

Claims, 8 Drawing Figures

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US Patent Sept. 23,1975

Sheet 1 of 2 3,907,366

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US Patent

Sept. 23,1975

Sheet 2 of 2

3,907,366

FIG 2

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FIG 6

3,907,366

METHOD AND APPARATUS FOR MINING COAL OR OTHER SOLIDS IN FLOODED MINES

BACKGROUND OF THE INVENT ION

Presently, about SO percent to 55 percent of coal mined in the United Stated comes from strip mining or surface mines. Technology has moved fast in surface mining. The cost is low and the process is efficient and safe, and recovers about 85 to 95 percent of the coal mined. Traditional underground mining in deep shafts and tunnels, on the other hand, is much more costly, very dangerous and recovers only about 50 to 55 percent of the underground coal. The problem is that about 90 percent of the domestic coal reserves lie below 150 feet, and therefore have far too much overburden to allow the strip mining approach economically. Therefore, new safe and economical subterranean mining technology must be created to make the huge coal reserves of the United States available in a relatively short time in order to satisfy the rapidly growing demands for energy. This invention is believed to represent a major advance and also a radical change in underground mining technology, and it is expected that the practice of the invention can be a major step in releasing and making readily available the deep coal reserves of this country.

The many hazards of traditional subterranean mining are well recognized and include, among others, explosions, cave-ins and flooding. The concept behind the present invention is to convert one of these major hazards or problems, namely flooding, into a solution and by doing so automatically solving many of the other problems incident to deep mining. The concept of the invention involves the deliberate flooding with water of the entire mine including its shaft and branch tunnels as the mine is being dug. Some existing mines and abandoned mines may also be revitalized by utilizing the new techniques of this invention.

Some important features of the invention may be summarized as follows:

1. The new mining system utilizes deliberately flooded subterranean mines in conjunction with completely submersible mobile, steerable and remotely operated mining machines. No human workers enter the mine shaft or tunnels at any time.

2. The mobile mining machine proper possesses floor and ceiling engaging track units and a leading mining head which cuts away the mined material and reduces it to sufficiently small particles for pumping with flood water as a slurry to the surface. While doing this, the mining machine is continuously producing a tunnel of sufficient dimensions to allow retrieval of the mining machine therefrom. The machine has a suction inlet for the mined material to draw the same as a slurry into a flexible pipe conveyor leading to the surface, which pipe transport system is equipped with a series of booster pumps.

3. The mining method utilizes the flood water in the underground mine for the multiple purposes of (a) acting as the medium for transporting mined material to the surface; (b) acting as a buoyant to assist in the movement and support of the pipe transport system; and (c) utilizing the pressure of the flood water to counteract the crushing pressure of the over-burden, thereby reducing or eliminating mine roof cave-in or surface subsidence. This also reduces or eliminates the need for props and braces under the mine roof.

4. The mobile mining machine which operates in the flooded mine tunnels includes an endless crawler track unit operating on the floor of the mine and a similar track unit operating against the mine ceiling. The ceiling unit is equipped with suitable power means to insure constant pressure of the track against the ceiling or roof, and automatic adjustment to compensate for surface irregularities or varying distances between mine floor and roof. The two crawler track units exert heavy forward pressure on the cutter head of the mining machine. The ceiling traction unit also compensates for reduced machine traction caused by buoyancy in the flooded tunnel, and enables the machine to negotiate the steeply inclined mine shaft and to mine slanted seams of coal.

5. The apparatus used in the practice of the method further includes a sectional flexible pipe transport system for the mined slurry, and the system employs a series of axial flow submersible booster pumps along its length which are only slightly larger in diameter than the pipe and which lack protrusions likely to hang up on corners or objects. The integrated booster pumpflexible piping is completely portable so that it can be moved freely in and out of the mine through relatively small openings. It features quick-release couplings for individual pipe sections and booster pumps to allow easy assembly and disassembly of the transport piping at the mine opening and also facilitating the cleaning of possibly clogged pipe sections or pumps.

6. The flexible slurry transport piping has an internal integrally molded spiral thread-like element tending to prevent solids from settling in the pipe and thereby reducing clogging.

7. Power-driven reversible rubber-like rollers are employed to push and pull the flexible piping and booster pump assembly, which in turn will propel the submersible mining machine forwardly or rearwardly, the piping constituting the “umbilical cord of the machine. The propulsion rollers supplement the traction of the floor and ceiling crawler tracks of the mining machine. The rollers are designed to accommodate pipes having slightly varying diameters and they also allow a passage of the booster pumps in the piping system.

8. The method and apparatus also contemplates the use above ground of coal cars having sieve-like bottoms whereby the mined coal slurry can be transported quickly and directly from the cutter head to the coal car in one continuous operation, with the water draining from the bottom of the car and flowing back into the mine for reuse.

9. The flooded mine is formed with a slanting mine shaft rather than a vertical shaft to facilitate the movement of the track mining machine into the out of the mine and to reduce the bend radii of the flexible transport pipe. The slanting mine shaft is feasible because of flood water pressure therein tending to prevent cave-in of the shaft.

Other features and advantages of the invention will become apparent during the course of the following description.

DESCRIPTION OF DRAWING FIGURES

FIG. 1 is a partly schematic side elevation of. apparatus employed in the new mining method and showing the same in relation to a mine shaft and tunnels and certain ground level components. ιύ

FIG. 2 is a partly schematic plan view of the system.

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FIG. 3 is a side elevation of a remotely controlled submersible self-propelled mining machine and associated elements.

FIG. 4 is an enlarged transverse vertical section through flexible transport piping taken on line 4—I of FIG. 1.

FIG. 5 is a fragmentary horizontal section taken on line 5—5 of FIG. 4.

FIG. 6 is an enlarged vertical section through an axial flow booster pump.

FIG. 7 is a fragmentary vertical section taken through transport pipe moving means.

FIG. 8 is a transverse vertical section taken on line 8—8 of FIG. 7.

DETAILED DESCRIPTION

Referring to the drawings in detail, a steeply inclined mine shaft 15 descends from the bottom of a relatively shallow well or cavity 16 for make up water supplied by a pipe 17 above ground. Several subterranean completely mined out tunnels 18 are indicated leading from the shaft 15, and these tunnels, along with the shaft, are completely flooded with water. At a lower level, a partially mined flooded tunnel is indicated at 19 and in broken lines in FIG. 1 an extension of the mine shaft is indicated at 15' along with another tunnel 19', to be subsequently formed during the practice of the : method.

The coal or other solids mining apparatus proper is shown particularly in FIG. 3 and is designated in its entirety by the numeral 20. This mining apparatus or unit is also shown in FIG. 1 actively operating within the partially formed tunnel 19 and working on an unmined coal seam or vein therein. The apparatus 20 consists of a lower crawler track unit 21 which engages the floor 22 of the mine tunnel and a similar overhead crawler track unit 23 which engages the ceiling 24 of the particular mine tunnel 19 shown in FIG. 3. Both of these traction units 21 and 23 are powered either electrically or by hydraulic motor means, which is completely submersible and adapted to be remotely controlled from a control station, not shown, at ground level. The overhead crawler traction unit 23 is borne up by adjustable hydraulic power cylinders having extensible rods 26 coupled to the frame 27 of the overhead traction unit. The power cylinders 25 cause the overhead traction unit to bear firmly and constantly against the ceiling 24 and to adjust automatically for ceiling irregularities and for variations in the distance between the tunnel ceiling and floor. The overhead unit 23 supplements the traction of the lower crawler unit 21 in producing sufficient forward pressure on the mining head 28 of the machine which may consist of a gang of hammers operated hydraulically or electrically or. in some instances, powerdrive rotary cutter. The overhead traction unit 23 additionally compensates for lost traction at the unit 21 due to the buoyant effect of the flood water, and the dual traction units enable the mining machine to negotiate steep inclines including the entrance and exit shaft 15.

The mining head 28 is pivoted at 29 to an articulated boom having sections 30 and 31. The head 28 is adjusted on its pivot 29 by a remotely controlled power cylinder 32 and the forward boom section 30 is similarly adjusted on pivot 33 by another power cylinder 34. The entire boom is raised and lowered about a fixed pivot 35 on the lower Crawler unit by a main elevating cylinder 36. The head 28 may be adjusted up or down and to the left or right within the tunnel and is sufficiently wide to produce a tunnel whose width slightly exceeds the width of the mobile mining machine, so that the latter may be steered therein and may be more readily retrieved at required times.

A large electric or hydraulically operated jet or centrifugal pump 37 is provided on the mining machine to suck a slurry of coal particles and water into a suction inlet 38 near the mine tunnel 4, or into an alternate inlet, not shown, immediately adjacent the mining head 28. In either case, the disintegrated coal with water in slurry form is sucked through an inlet pipe 39 and through the pump 37 to the first section 40 of a flexible transport pipe which is employed to transport the coal slurry from the tunnel 19 and through the shaft 15 to a ground level collection point.

The flexible transport pipe designated in its entirety by the numeral 41 consists of a multiplicity of equal length flexible pipe sections 42 which may be stored on a suitable rack 43 at ground level near the mine shaft entrance well 16. Each pipe section 42 is constructed of a tough elastomer internally reinforced with steel strands in its wall. An internal helical rib 44 similar to a screw-thread is molded in the pipe section 42 to counteract the tendency for solids in the slurry to settle out and clog or block the transport pipe system. Additionally embodied in the pipe sections 42 making up the transport pipe 41 are conduits 45, 46 and 47 for electrical power cable, control cable means and hydraulic fluid, all necessary to operate and control the mobile mining machine 20 which is tethered to the transport pipe 41. The main control center for the machine 20 is at ground level at any convenient location and is omitted from the drawings for the sake of simplicity.

Also contained in the flexible transport pipe 41 at regular intervals are axial flow booster pumps 48, having quick release couplings of any conventional form adapted to connect with mating coupling parts of flexible pipe sections 42. The pumps 48 need only be slightly larger in diameter than the transport pipe, FIG. 7, and are contoured at their ends where they join with the pipe sections 42 so as to be free of abrupt shoulders or projections likely to hang up in narrow passageways. Preferably, each booster pump 48 has a bladed impeller 49 operated by a central pump motor 50. Guide vanes 51 extending radially inwardly of the pump casing 52 also serve to support the motor 50 of each pump.

An above-ground rack 53 for the support and storage of disassembled booster pumps 48 is provided next to the rack 43, as shown in FIG. 2.

A means for propelling the flexible transport pipe into the mine or for extracting it is also provided above ground in the form of a pow er unit 54. This power unit includes a pair of powered reversible rubber-like rollers 55 having radial elastic teeth 56 thereon adapted to engage the flexible pipe line to aid in pushing or pulling it together with the integrated booster pumps. The yielding teeth 56 enable the drive rollers 55 to accommodate piping or pumps of slightly varying diameters. The power unit 54 is not only used to feed the flexible piping into the mine and to extract it therefrom, but also assists in the pushing or pulling of the submersible mining machine 20 tethered to the piping.

Above the ground, a horizontal section of the flexible transport pipe 41 is supported by a bed of rollers 57, and its discharge end remote from the mine shaft 15

3,907,366 &lt; 5 leads into or is suitably coupled with a coal storage hopper or hopper cars, one such car being:diagrammatically illustrated by the numeral 58, It is contemplated that this car or hopper will be equipped with, a sieve bottom so that the water from the coal slurry can drain immediately from the bottom of the car or hopper into a return drain pipe 59 returning the water to the mine shaft for recycling or reuse. By this system, the mined coal slurry can move directly from the cutter head 28 through the transport pipe 41 to the coal car or hopper in a continuous and rapid operation, with the drain water flowing back into the mine.

The above is a complete description of the basic essential elements of apparatus employed in the practice of the mining method. Many additional refined apparatus features are contemplated throughout the system but need not be detailed herein for an adequate understanding of the mining method and the basic apparatus. However, certain concluding statements may prove helpful in understanding the complete nature of the invention. In reference to the mobile mining machine 20, the remotely controlled boom structure 30-31 will operate similarly to the boom of a back-hoe. The adjustable mining head 28 will be capable of cutting a swath slightly wider and higher than the machine 20, to facilitate backing the machine out of the tunnel. While the machine 20 is designed for operation in a subterranean mine, it could also have utility for mining or tunnel digging operations beneath lakes, rivers or even the sea. In any case, the ultimate objective of the invention is to provide a system which is completely automatic and remotely controlled, with no human beings required to enter beneath the surface of the earth.

Another significant feature not yet mentioned is that the flood water in the tunnel 19 serves to cool the mining head 28 which is fully submerged. The flexible piping is designed for nearly neutral buoyancy in the flooded mine. The invention eliminates entirely the traditional necessity for creating and maintaining a livable environment inside of the mine and this is a very significant economic advantage, as well as a safety advantage.

The invention employs petroleum drilling pipe assembly techniques, except that the piping is assembled horizontally instead of vertically, and the flexible pipe assembly includes the insertion of the booster pumps 48, as needed.

Various subterranean tunnel patterns may be created with the apparatus 20 including straight parallel tunnels. zigzag, in straight lines, or on arcuate paths, involute and many others. Increased utilization of coal underground is achieved since there will be no necessity for creating and maintaining permanent coal pillars in the mine tunnels for support and safety. Other inherent advantages of the method will be readily apparent to those skilled in the art.

It is to be understood that the form of the invention herewith shown and described is to be taken as a preferred example of the same, and that various changes in the shape, size and arrangement of parts be resorted to, without departing from the spirit of the invention or scope of the subjoined claims.