Abstract: A subterranean hydraulic mining system for mining soft sedimentary deposits, such as coal, in which a shaft is sunk through spoil layers, such as sand, dirt, clay, sedimentary deposits, slate, etc., to the sedimentary deposits, such as a coal vein. A second shaft is drilled from the surface to the coal vein in proximity to the first shaft and a small shaped charge is placed down the first shaft and directed toward the termination of the second shaft. A pipeline containing a directive nozzle is then directed down the first shaft with the nozzle oriented toward the second shaft and water and air pumped therethrough. A line is dropped through the second shaft terminating in a hydraulic elevator with water pumped down the shaft and up through the hydraulic elevator.

Abstract: A drag bit excavating device comprising a core extending along an axis; a bit carrier supported on the core; cutter bits supported by the carrier along a three dimensional spiral having constant pitch and increasing radius along at least a portion of the axis, the carrier being relieved to provide radially extending spaces between the turns of the spiral; a frame supporting the core, carrier, and bits for rotation about and advance along the axis; and a drive to provide rotation, whereby the bits slot the material to be excavated while the material between portions of the resulting slot extends into the spaces to be subsequently broken away.

Abstract: A process for recovering underground fossil fuel deposits retained in an inorganic matrix wherein the deposit is contacted with an aqueous medium of anaerobic microorganisms for a time sufficient to produce particles of the deposit containing both the organic fossil fuel and inorganic matrix of a size capable of forming a slurry with the aqueous medium for pumping to the ground surface. At the ground surface, the particulates are separated from the aqueous medium of anaerobic organisms, the particulates further processed by efficient surface techniques to separate the organic carbon and hydrocarbon component from the inorganic matrix. The aqueous medium of anaerobic organisms is recycled to the underground fossil fuel deposit for further production of the slurry forming particles of the deposit. Spent inorganic matrix may be added to the aqueous medium of anaerobic organisms to provide solid support and nutrient for the organisms and to maintain the desired pH.

Abstract: Apparatus for forming bores and coal seams and the like and enlarging preexisting bores. A mining machine includes a nonrotatable body member, a conveyor in line with the body member, a pilot head, and a pair of wing cutters mounted to the body member for pivotal movement with respect to the body member. Structure is provided for moving coal or the like cut by the wing cutters during out-cutting toward the sides of the bore, the structure including a pair of shields, one associated with each wing cutter and disposed between the wing cutter and the body member and pilot head, and a generally conical member coaxial with the shaft for rotation of the pilot head. Stabilization of the body member, etc., within the bore is provided by a pair of wheel sets spaced along the length of the conveyor, and a pair of right angle guide members vertically displaced from the wheel structure of one the wheel sets.

Abstract: The invention relates to a method and apparatus for hydraulically mining friable carbonaceous material such as coal or other suitable materials wherein a feeder/breaker is placed in the entry with complete mining facilities mounted on this second machine including hydraulic monitors, one for cutting material from a seam or panel and, if desired, a second monitor for breaking and flushing the mined material in the form of a slurry for transport through the machine where it is mechanically broken and crushed to predetermined size and the solids/water slurry discharged into a flume for transport from the mine.

Abstract: Apparatus for guying a movable cutting machine equipped with a caterpillar drive and for moving the machine on ascending galleries has at both sides of the cutting machine tension members formed of chains or ropes and led over winches. The tension members are adapted to be fixed on both sides of the cutting machine, with the forward ends and the rearward ends of the tension members being adapted to be fixed at stationary locations of the gallery, preferably by means of rock anchors.

Abstract: A technique for mining coal or similar mineral employing existing auger holes or a specially drilled bore hole into the face of the coal, a guide anchor rod being inserted into the hole and having a pulley at its inner end, a first cable passing over the pulley pulls a coal recovery scoop into the hole, an additional cable is attached to the scoop and extends out of the hole to a winch which pulls the scoop and the coal out of the hole, and thereafter the first cable retracts the scoop into the hole to start another cycle of operation.

Abstract: There is provided a method for extraction of rock or ore according to the block caving principle comprising driving, at several levels, principally straight, parallel and horizontal drifts into the lower part of a block, choosing the distance between the drifts at each level so that remaining supporting pillars will cover at least 40% of the block area, undercutting the block from the drifts in such a way that the drift openings toward the undercut area and the drift coverings will be arranged in steps, the drift openings being utilized as draw-points for the caving material and the number of drift levels being chosen with regard to desired horizontal distance along the direction of the drift between the draw-points at adjacent levels.

Abstract: A method of mining a large underground seam of mineral such as coal is described in which a first cylindrical shaft is drilled from the surface of the earth down to the mineral seam. A portion is enlarged at the base of the first shaft as a work room. A first radial shaft out to a selected radius R is drilled by conventional methods with the roofs supported by means such as hydraulic chocks which can be extended and moved selectively as the line of drilling progresses. When the first shaft is drilled a continuous miner working on a short face method of mining is directed radially from the work room and is advanced outwardly until the width of the first radial shaft is such that the original wall of the first shaft has been cut away. The direction of the miner is then turned to be parallel to the first horizontal shaft and a short wall cutting advance is made to cut away the first wall of the first shaft and in effect drill a second shaft having a first wall spaced by the width of the cutter.

Abstract: A coal mining apparatus and its method of use in which a continuous mining machine removes and transfers cut material reducing airborne respirable coal dust generated in the cutting and collection process. The conventional high speed head rotating with the bits going forward at the top is replaced by a triangular shaped dished out linear cutting head rotating with the bits mounted at the apexes going rearward at the top. This produces a box cut in the mine face with a square cross-section. After the head has made a box cut by sumping the full head diameter beginning at the mine floor, it is sheared upwardly producing a linear shear cut. This shear step is at a constant depth equal to the complete cutting head diameter. The modified cutting head is used as part of the loading and transfer mechanism.

Abstract: A shaft is formed from ground level downwardly to a subterranean seam of coal or other solids following preliminary survey procedures to locate the seam and establish its dimensions. A passage is cut radially into the coal seam and away from the shaft near the bottom thereof while coal cuttings are removed and delivered to ground level. The seam is then cut on an arcuate path centered on said shaft along the entire length of the radial passage while coal cuttings continue to be removed and delivered through the shaft to ground level. The mining apparatus is modular and comprises plural mining modules to be placed in the coal seam by a placement and advancing unit which is lowered in the shaft. A rotational driving unit is subsequently lowered in the shaft to drive coupled mining modules in unison through the coal seam on said arcuate path.

Abstract: An hydraulic mining apparatus and method wherein the mined aggregate is separated into dry, relatively large aggregate pieces for dry conveyance and wet, relatively small aggregate pieces for wet conveyance. In the preferred embodiment, the method and apparatus provides for reducing any oversized large aggregate pieces in size so that the large pieces do not exceed a predetermined maximum size. Size reduction is provided by a mechanical breaker and wet, relatively small aggregate is separated out of the mined product prior to the breaking step. The apparatus is embodied in a feeder-breaker mechanism wherein a conveyor running lengthwise of the mechanism first subjects the total mined product to size separation or classification, then directs the larger aggregate pieces through the breaker and, finally, discharges the breaker treated pieces to a dry conveyor. The separated wet, relatively small aggregate pieces are collected within the mechanism and pumped away.

Abstract: An apparatus for cutting a deep slot, having a large depth to thickness ratio, in earth formations, which includes two main components, a motive means and a cutting assembly; the motive means, such as a crawler tractor, supports the projecting end of the cutting assembly, supplies a small portion of the driving force needed to advance the cutting assembly, and provides, through various connections, power, control functions, and the fluids required for operation of the cutting assembly; and the cutting assembly, extending the full depth of the slot along its advancing edge, includes an elongated support, a reciprocating cutter bar mounted on the leading edge of the support, a passage incorporated in the support for transmitting a fluid, generally a high gel strength clay paste, along the support and discharging the fluid in the interior of the slot, in a sufficient amount and under sufficient pressure to resist the earth pressure tending to close the slot and to provide a major portion of the force necessary t

Abstract: A drilling apparatus comprises a support structure adapted to be moved on rails to position a drilling assembly mounted thereon adjacent to a selected drilling site. The drilling assembly includes a carriage movably mounted on the support structure for longitudinal movements thereon and a shroud secured on the carriage and having an auger rotatably mounted therein. A cutting edge, having a square configuration, is disposed adjacent to a forward end of the auger and at least one double-acting hydraulic cylinder is interconnected between the support structure and the carriage to aid in pushing the auger and cutting edge through material to form an opening having a square cross section. Upon full extension of the auger and cutting edge, a second drilling assembly may be attached rearwardly on the first-mentioned drilling assembly to increase the overall penetration capabilities of the drilling apparatus.

Abstract: A mining machine suitable for cutting roadways in coalmines comprises a cutting head, a conveyor for moving mined material rearwardly of the machine and a discharge conveyor for unloading the mined material to one side of the machine. As the machine advances the discharge conveyor can be used selectively to unload coal onto a stage loader and other material into packholes, thereby saving labor. The discharge conveyor may be pivotable about horizontal and/or vertical axes, longitudinally extendable or movable relative to the machine or cutting head to obtain maximum control over the area in which it discharges material.

Abstract: A method and apparatus for hydraulic mining wherein the mined product is reduced to a pumpable form. The apparatus includes a jet monitor for dislodging the mined product from its in situ state, a feeder-breaker for receiving the mined product, preliminarily separating the pumpable constituent of the product and then subjecting the remaining product to successive breaking and separating steps until the entire product is in a pumpable state. The feeder-breaker is also provided with a sump to collect the pumpable product and pump means to convey the product from the sump under pressure, whereby transport of the product is not dependent on gravity. In the preferred embodiment, the feeder-breaker is provided with a secondary jet monitor to reduce oversized constituents of the mined product to a size suited for the successive separating and breaking steps.

Abstract: An apparatus and method for excavating tunnels with a shield and slurry while detecting and preventing excess excavation in high water content soft ground wherein, in each of feeding system of slurry to tunnel face and discharging system of a mixture of slurry and excavated soil or the like as well as gushing water from the tunnel face out of working area, the respective volumes of the slurry and mixture passing through the respective systems are measured in positions close to the tunnel face, the volume of the excavated soil or the like is determined with the difference between both volumes while the amount of propelling a tunnelling machine is determined as an excavated space volume of the tunnel, the respective values of the excavated soil volume and excavated space volume are compared with each other, whereby the amount of propelling the machine, fed amount of the slurry or discharging amount of the mixture can be properly adjusted so that the difference between said values will be made substantially zero

Abstract: A miner especially adapted for high-production mining of low-coal seams (24-36 inches thick) while providing maximum miner safety and complying with applicable federal safety regulations. One or more cutting heads rotatable about the vertical axes are provided along with electric motors for rotating the heads. The heads are mounted for reciprocal longitudinal movement along the cutting face, and hydraulic cylinders, or the like, are provided for reciprocating the heads so that they move toward each other during shearing. A paddle-type conveyor continuously (even during sumping) conveys the cut coal away from the coal face, substantially perpendicular thereto through the formed tunnel. Hydraulic rams associated with roof-supporting and anchoring means are provided for sumping the cutting heads. A curtain assembly or the like contains the dust generated during cutting to a confined area adjacent the cutting face, and an exhaust fan or fans continuously draws the dust away from the confined area.

Abstract: A push-pull mining system comprising a pre-formed arrangement of personnel entry shafts, laterally extending service tunnels, flumes in the form of ditches extending substantially throughout each service tunnel, a holding tunnel at one side of each service tunnel and a chamber below the lowermost service tunnel at the end opposite to the holding tunnel for receiving a separation tank, a slurry mix tank, and an underground water reservoir. A mobile mining unit, comprising a mining machine at each end and carriers therebetween, is of substantially the same length as the holding tunnel. The mobile mining unit moves across the service tunnel to mine the opposing face and form a working tunnel which when finished is of the same length as the mobile unit. A mobile water station is mounted in the service tunnel and is connected to the mid-carrier which conveys the water to the mining machine at the end which is effective.

Abstract: A method of strip mining in which a plurality of vertical shafts of square cross section are formed closely adjacent to one another with each shaft extending through overburden and a layer of valuable material such as coal. As spoil is removed in forming one shaft it is conveyed to a previously formed shaft and deposited therein. The apparatus includes a casing of square cross section, a cylindrical auger casing within the square casing, an auger rotatable in the auger casing and a square cutter at the lower end of the square casing. The latter is slidably mounted on a vertical track and is power driven vertically to force the cutter into the earth formation being worked. The auger is rotated under power to cut into the earth formation and remove spoil and coal therefrom. The upper end portions of both casings are formed with two sets of aligned discharge ports. A movable closure is provided for each set and a rake for each set.

Abstract: The method of mining coal entails the use of crude petroleum under high pressure together with elevated temperatures in hydraulic fashion to produce a hybrid oil-coal fuel. A powerful stream of oil is aimed at sections of coal strata to disintegrate the coal. The resultant slurry can be recycled for reuse in the mining operation with provisions being made for screening out the larger coal particles. When the oil-coal slurry reaches the desired consistency, it can be pumped for storage or pipeline delivery to consumers or processing plants.

Abstract: Disclosed is a method for mining minerals at depths where strip and deep mining methods are not practical or economical. After site layout, a plurality of generally parallel-spaced, elongated trenches are formed to expose the mineral bed. Continuous mining equipment is used to mine the minerals from the base of the trench. A conveyor is disposed in each trench to convey the mined minerals to one end of the site to a collection conveyor. After the minerals are mined from the base of the trench, mining tunnels are formed to the opposite sides of and generally perpendicular to each trench and adjacent one end thereof. The tunnels are extended distances at least several times the width of the trench and thereby form longwall mining surfaces. Longwall mining equipment is disposed in each tunnel and the minerals are mined by advancing the longwall mining equipment in a direction parallel to the trench and toward its opposite end. As the longwall mining equipment advances, the overburden caves behind the equipment.

Abstract: A mining machine comprises a laterally elongated cutting head including means for cutting an earth formation, a laterally elongated thrust transmitting column connected to and extending rearwardly from the cutting head, and a power head connected to the rear of the column and operative to thrust the cutting head forward into the earth formation by means of the interposed column. The column carries a non-thrust transmitting column conveyor for carrying fragments cut from the formation from the cutting head to the power head.

Abstract: The invention is to a method for the hydraulic mining of coal of varying hardness. It is described in particular as to coal of the type occurring in the Balmer Seam in British Columbia. By the method at least two parallel spaced entries are driven upward through a seam of coal. Monitors are positioned in each entry. Each monitor is horizontally and vertically pivotable, and has nozzle means from which a jet of water under a pressure of about 1900 - 2200 p.s.i. is emitted. The high pressure jet cuts the coal, which is then fed to a machine that breaks and crushes the coal into sizes wherein the resultant coal/water slurry will flow down a sloped flume into a dewatering station.The method further embodies differentially retreating along adjacent parallel entries by increments of desirably at least about 40 feet each.

Abstract: This invention relates to the recovery of valuable minerals from deposits thereof in the earth and is particularly directed to a method of mining which affords recovery of at least a major portion of a seam of valuable mineral lying relatively near the surface of the earth without seriously involving the destructive effects upon the environment, inherent in surface mining. In practicing the method a relatively small proportion of the overburden covering a seam of useful mineral is removed, for later replacement, and a proportion of the valuable mineral in the seam much greater than that underlying the removed overburden is recovered by operations conducted in the pit formed by removal of overburden from selected areas, the recovery of these portions of the mineral seam being conveniently accomplished by what is known as augur mining from spaced pits disposed in predetermined patterns relatively to the mineral seam.

Abstract: A method and apparatus for forming bores in coal seams and the like and enlarging pre-existing bores. A mining machine includes a non-rotatable body member, a conveyor, such as an auger, in line with the body member, and a pair of wing cutters mounted on the body member for pivotal movement with respect thereto. The wing cutters are movable from a first position wherein they are generally in line with the body member and conveyor, to a second position wherein they are disposed outwardly with respect to the body member. The wing cutters will be in their first position during movement into a bore, and will be moved to and latched in a second position during movement out of the bore. A pilot cutting head in front of the body member may also be provided. The wing cutters may comprise rotatable drums driven by cutting chains, and the drums are normally powered to rotate outwardly from the body member, in directions opposite to each other.

Abstract: A support displaceable along a tunnel or gallery floor by means of a caterpillar drive is provided with a rotatable milling tool that can be brought into engagement with a lower portion of a face wall and with a reciprocal hammer engageable with an upper portion of the wall. The miller is operated to cut or grind material off the lower portion so as to undercut the wall. Then the hammer is operated to chip or break off the upper portion of the undercut wall. Both the miller and hammer are mounted on adjustable and directable arms. The loosened rock is carried off by a scoop-transport belt arrangement.

Abstract: A self-propelled body portion has spaced parallel vertical plate members that form a longitudinal passageway in which is positioned an endless conveyor. The conveyor includes a material receiving end portion that is maintained in underlapping relationship with the conveyor of a continuous mining machine that dislodges material from the face of the mine and deposits the material onto the receiving end portion of the conveyor. The conveyor transfers the mined material longitudinally of the body portion to a discharging end portion that pivots about a vertical axis relative to the main conveyor and discharges the mined material into a shuttle car. A pair of horizontally extensible drill booms are pivotally mounted to opposed sides of the body portion to swing laterally toward and away from the body portion.

Abstract: A mining system for extraction of coal or the like from narrow seams has a conduit system for pneumatic conveyance of mined material. A leading section of apparatus comprises a cutter head assembly driven by an air motor which exhausts into the conduit system. The leading section includes further an anchoring means which is changeably mounted thereon to permit advance of the leading section and cutter head assembly, and ground contact means for pivoting of the cutter head from side-to-side.

Abstract: A hydraulic mining system for a mine including a plurality of horizontal stopes each of which has a mining face. The apparatus comprises a main slurry mix tank at the lowermost stope, a hydraulic mining device in each stope, slurry forming mechanism in each stope for converting mined ore into slurry form, a flexible conduit extending from each stope to the main slurry mix tank for conveying mined ore in slurry form to the mix tank, an upflow tube having its lower end at said slurry mix tank and extending upwardly to the ground surface, and a pump for moving slurry upwardly in said tube.

Abstract: A tunnel driving installation has an advanceable support shield and cutting means co-operating at the front end of the tunnel and a continuous tunnel lining disposed rearwardly of the support shield and constructed from individual lining sections. In order to store and transport the tunnel lining sections within the tunnel lining apparatus is provided which comprises storage stations respectively located at the front and rear regions of the tunnel and a trolley vehicle for moving back and forth between the stations. The trolley vehicle has a container which serves to receive debris removed by the cutting means, and beneath the container the vehicle has shaped plates which serve to locate and support a series of lining sections. Both storage stations are composed of T-shaped rails laid on the tunnel floor so that the vehicle can pass over the rails.

Abstract: This invention concerns a ripping platform for use in a mine to support the roof above an excavated stratum of mineral to facilitate excavation or ripping away of the roof to provide a roadway. In accordance with the invention a ripping platform to receive and distribute debris from a mine roof comprises a trough for location under the mine roof, a first deck within the trough reciprocable in a direction lengthwise of the trough at a level above the bottom of the trough, reciprocating mechanism for the deck located in the trough under the deck, an impeller member secured to one end of the first deck and extending downwardly from the deck to the bottom of the trough, and a second deck in the trough closely engaging the first deck, the first and second decks and the impeller defining a zone between the decks and the trough bottom that is substantially isolated from the debris, the said zone containing the reciprocating mechanism.

Abstract: In order to concentrate coal slurry from a plurality of mine faces being pumped through a plurality of individual pipes, a shallow sump is formed by digging a trench along a mine tunnel and the individual pipes empty into the sump. The product, such as coal, is allowed to settle to the bottom where it is picked up and pumped out of the mine at a controlled concentration, thereby improving the pumping efficiency of the pipeline system.

Abstract: This invention comprises two improved mining methods as such and combined with mining equipments for the mining and rock industries. The first, called the screw-mining-method, comprises benches which rotate around a turning-point area in a downwardly sloping screw shaped path. The benches are positioned radially to the turning-point area which contains a shaft or other transportation means between two points located at different altitudes. The second, called a method with horizontal-radial-rotating benches, operates similarly to the first method except that the benches rotate solely in a horizontal plane rather than in a downwardly sloping path. The method and equipments are adapted for use with material such as rock, ore, coal and any other commercially useful, as well as mineral materials excavated from the earth's crust.

Abstract: A method for recovering coal from deeply buried deposits comprising drilling a hole down into a coal seam, filling the hole with water, and periodically detonating an explosive charge at the bottom of the water-filled hole. The water transmits the explosive shock wave to the face of the coal seam, thereby fracturing and dislodging the coal. The resulting suspension of loose coal in water is then pumped to the surface where the coal is recovered and the water is recycled to the mining operation.

Abstract: A sectional scraper device which is foldable in zig-zag position by remote pulling means and which can be let down through a clad bore hole and can be deviated to follow layers of mineral to be mined by a to and fro movement of the scraper device combined with transport of loosened minerals by liquid circulation through the bore hole. The scraping action may be strengthened by the action of liquid jets emanating from the scraper device.

Abstract: A cutter head, or excavating bucket; having a forward edge formed for penetrating earth formations, and which may be in the form of teeth; for earth working operations, especially for dredging operations, and the like, and having a vibrator mechanism associated therewith for enhancing the penetrating action of the forward edge of the cutter into an earth formation. Associated with the cutter is a crushing structure which crushes large boulders taken by the cutter down to smaller sizes. The material taken by the cutter, including the crushed boulders, can be removed from the cutter and crusher by water which is drawn therethrough with he material being delivered to a refuse place or to a further processing station.

Abstract: The invention is directed to a method of in situ extraction of a constituent of a rock formation, e.g., copper deposits or particular petroleum deposits as found in oil shale, and to a method of preparing the rock formation for in situ extraction of the rock constituent. Various embodiments of a side excavating machine are also disclosed for preparing the rock for in-situ extraction of a constituent therefrom. The excavating machine breaks the rock in-situ in a manner to form a narrow, horizontal flow-directing chamber in the rock-filled with fluid-permeable broken rock.

Abstract: Coal mining apparatus for removing subterranean material with minimal disruption of the overburden includes a mobile underground mining machine having rotary cutters mounted on the front of the machine for drilling coal in a coal deposit. The underground machine is track driven with an overhead protective shield to support the overburden above the machine as it digs into the coal deposit. The protective shield is slanted downward toward the rear of the mining machine to gradually lower the overburden as the mining machine passes under, thus replacing the excavated coal while minimizing disturbances on the surface. An elevator shaft is mounted on the underground mining machine and extends vertically upward to the earth's surface. A mobile track vehicle is attached to the elevator shaft at the surface and is coordinated to move in synchronization with the underground mining machine.

Abstract: An apparatus and process for harvesting deep-sea particles, such as nodules, from a substantially planar deep-sea bottom is disclosed. A vessel on the surface tows a heavier than water sled along the ocean bottom. Towing occurs through a single towing strip connected to the sled at the lower end, connected to the vessel at the upper end, and extending angularly downward from the vessel to the sled. The towing strip includes an integral elevator mechanism comprising in the preferred embodiment a series of buckets having perforated sides conveyed by and on an endless belt traveling on the towing strip. The series of buckets on the endless belt empties a concentrator collector having the accumulated and harvested particles in the towed sled. The buckets ride upwardly from the sled to the surface vessel on a first track on the towed strip. The bucket contents are then emptied at the surface typically within the vessel, and thereafter are reconveyed to the sled on a second and separate track on the towing strip.

Abstract: A roller crusher is carried by a coal cutting mining machine which is, in turn, carried by a gantry for movement along the frame of a longwall face conveyor. The roller crusher is attached to the coal cutting machine by a U-shaped frame having hinge pins for pivotal movement thereof about a horizontal axis at the end of the machine which faces toward the oncoming stream of coal on the conveyor. The U-shaped frame supports a drive motor that is, in turn, coupled by a gear drive to the roller crusher. A piston and cylinder assembly is controlled to adjustably position the U-shaped frame and thereby the roller. The mining machine has support arms that are pivotal about horizontal axes and carry coal cutting drums to project into the working face of the mine.

Abstract: An underground, improved slurry transportation system consists of a first and second vertical cavity. Both cavities have a vent means to the surface of the earth. Slurry input means from a plurality of mine faces communicates with the upper portion of the first vertical cavity and slurry output means communicates with the lower portion of the first vertical cavity. A pump connected to the slurry outlet forces the slurry from underground through a slurry handling pipe system to a preparation plant located on the surface of the earth.Water is added to the second vertical cavity by an inlet communicating with the upper portion of the cavity. Water is also provided to the first cavity, and valves are provided to add water to either the first or second cavity upon demand. A decant system is also provided between the first and second cavities to remove any excess water that may accumulate in the first cavity.

Abstract: Method and apparatus for excavating and removing a settled body of discrete mineral solids (e.g., a tailings pond from a mining operation) by procedures which progress downwardly from the surface of the body. High pressure streams of liquid are traversed along a path in a pulping zone lowermost in first region of the body. The liquid forms a pumpable slurry with the mineral solids in the zone, and the slurry is then pumped from the zone leaving an undercut cavity sufficient to cause collapse of the overburden of solids. The collapsed overburden is then formed into additional pumpable slurry which is removed by pumping. Successive stages of excavation are carried out by moving the streams of liquid downwardly to a second region where the foregoing steps are repeated. In the apparatus a caisson is disposed vertically in the body and stabilized by means of a plurality of circumferentially positioned pilings.