Method and apparatus for excavating settled body of solids

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. A plurality of high velocity nozzles are mounted in the caisson to direct liquid streams into a pulping zone surrounding the caisson. The slurry which is formed in the pulping zone flows through portals in the caisson into a slurry sump in the lower end of the caisson where a pump removes the slurry through a discharge line leading from the caisson. In one embodiment the caisson is fixedly secured to the caisson and jets are provided to direct liquid streams into regions below the lower ends of the caisson and pilings to sink the apparatus downwardly to the next lower region for additional stages of excavation. In another embodiment, the caisson is mounted for relative vertical movement with respect to stationary pilings.

We claim: 
     
       1. A method for removing a settled body of discrete mineral solids including the steps of directing a stream of liquid through at least one nozzle substantially laterally into a first pulping zone, the nozzle being located at a first predetermined elevation below the upper surface of said body whereby the liquid forms a pumpable slurry with the mineral solids in said zone, pumping the slurry from the zone, traversing the liquid stream through a predetermined path in said zone to form an undercut cavity in said body sufficient to collapse the overburden of mineral solids overlying said cavity, causing the collapsed overburden of mineral solids to be formed into additional pumpable slurry with said liquid, pumping the additional slurry from said zone, directing additional liquid to a region below said nozzle to cause the same to sink downwardly through said solids to a second predetermined elevation below said first elevation, directing said stream of liquid into a second pulping zone located at said second elevation, and repeating said steps of pumping the slurry from said second zone, traversing the liquid stream through a predetermined path in said second zone to form an additional undercut cavity sufficient to collapse the overburden of mineral solids thereabove, causing the collapsed overburden to be formed into additional pumpable slurry with said liquid, and pumping the additional slurry away from said second zone. 
     
     
       2. A method as in claim 1 in which the stream of liquid is moved successively to a plurality of regions each located at successive elevations below said first elevation, and the mineral solids within each region are removed by repeating in each region the steps of directing streams of liquid into pulping zones to form a pumpable slurry, pumping the slurry from the zones, traversing the streams through predetermined paths in the zones to cause collapse of overburden in the regions, causing the collapsed overburden to be formed into additional pumpable slurry, and pumping the additional slurry from the respective zones. 
     
     
       3. A method of removing a settled body of discrete mineral solids capable of being formed into a pumpable slurry by nozzle means and slurry pump means .Iadd.which are mounted within a housing structure.Iaddend., including the steps of establishing the nozzle means and slurry pump means in the body with the nozzle means located at a first predetermined elevation below the upper surface of said body, .[.directing.]. .Iadd.moving .Iaddend.at least one stream of liquid from said nozzle means .[.into a path.]. .Iadd.back and forth relative to the housing through an arc .Iaddend.extending substantially laterally therefrom to define a pulping zone whereby the liquid forms a pumpable slurry with the solids within said zone, pumping the slurry from the zone with said slurry pump means until the solids within the region adjacent said nozzle means are substantially removed, directing additional liquid into a region underlying said structure to form additional pumpable slurry with the mineral solids and pumping the additional slurry away from said underlying region to sink the nozzle means and slurry pump means downwardly to a second region with said nozzle means located at a second predetermined elevation below said first elevation, and repeating the steps of .[.directing.]. .Iadd.moving .Iaddend.at least one liquid stream from said nozzle means into a path to define an additional pulping zone and pumping slurry from said additional zone until the solids within said second region are substantially removed. 
     
     
       4. A method as in claim 3 in which the settled body comprises a tailings pond associated with an ore mining operation, and said steps are repeated in a plurality of regions of the pond to remove the mineral solids therefrom.  .[.5. A method as in claim 3 in which said structure includes a caisson, and said caisson is stabilized by a plurality of pilings positioned circumferentially around said caisson and extending vertically into the body of mineral solids adjacent thereto, and the step of moving the nozzle means and slurry pump means includes directing liquid into regions adjacent to and underlying said pilings whereby the liquid forms a slurry with the mineral solids therein sufficient to allow the pilings to sink by gravitational action with the caisson through the slurry thus 
     
     
        formed..]. 6. A method as in claim 3 in which said structure includes means defining a sump positioned at the lower end of the structure and means forming a portal opening in the structure to direct slurry into said sump, including the steps of directing said stream of liquid through said openings to establish said pulping zone laterally adjacent the openings, causing said pumpable slurry to flow by gravitational action from the pulping zone through the portal openings and into said sump, and causing the slurry in the sump to be pumped to a zone remote from the structure. 
     
     
           A method as in claim 3 in which said structure includes a capsule, and said capsule is mounted for vertical movement with respect to a plurality of stabilizing pilings positioned circumferentially around said capsule and extending vertically into the body of mineral solids adjacent thereto, and the step of moving the nozzle means and slurry pump means includes directing liquid into regions adjacent to and underlying said capsule whereby the liquid forms a slurry with the mineral solids therein sufficient to allow the capsule to sink downwardly by gravitational action 
     
     
        relative to the pilings. 8. Apparatus for removing discrete mineral solids from a settled body of the same comprising a .Iadd.caisson .Iaddend.structure having a side wall, a lower end adapted to extend below the upper surface of the body when the structure is positioned therein, .Iadd.stabilizing means for supporting the caisson structure at a selected region within the body, .Iaddend.means forming a portal opening through the sidewall providing fluid communication from a region of the body surrounding said portal opening means into said lower end, nozzle means .Iadd.mounted within the caisson structure .Iaddend.forming a stream of liquid extending substantially laterally outwardly through the portal opening means into said region, .Iadd.means for moving the nozzle means with respect to the caisson structure to move the liquid stream in alternate rotational directions across an arc .Iaddend.whereby the liquid forms a pumpable slurry with the solids within a portion of said region defining a pulping zone, and means to pump said slurry to a zone remote 
     
     
        from the structure. 9. Apparatus as in claim 8 .Iadd.in .Iaddend.which .[.includes.]. .Iadd.said stabilizing .Iaddend.means .[.to stabilize.]. .Iadd.supports .Iaddend.said structure within said body with said structure lowered in position at said first predetermined elevation below the upper surface of said body, and means to move said structure downwardly to a second elevation below said first elevation whereby operation of the nozzle means and slurry pump means removes mineral solids 
     
     
        from a second region of said body below said first region. 10. Apparatus as in claim 9 in which said structure includes a caisson carrying said nozzle means and slurry pump means, and said stabilizer means comprises a plurality of pilings secured to said caisson and circumferentially positioned therearound to extend vertically into said body of solids 
     
     
        whereby said caisson and pilings move downwardly together. 11. Apparatus as in claim 9 in which said structure includes a capsule carrying said nozzle means and slurry pump means, and said stabilizer means comprises a plurality of pilings circumferentially arranged around said capsule and extending vertically into said body of solids, together with means mounting said capsule for vertical movement with respect to said pilings. 
     
     
         2. Apparatus as in claim 11 which includes means forming a platform at the upper ends of said pilings, together with hoist means on the platform 
     
     
        to raise and lower said capsule. 13. Apparatus as in claim 12 which includes means forming a service bridge extending from said platform to 
     
     
        the perimeter of said body. 14. Apparatus as in claim .[.9.]. .Iadd.11 .Iaddend.in which said means mounting said capsule for movement with respect to said pilings includes guide means comprising a plurality of guide shoes mounted for movement with said capsule, each guide shoe extending radially outwardly from the capsule into sliding contact with the outer surface of respective ones of said pilings.  .[.15. Apparatus as in claim 9 in which the means to move the structure downwardly comprises means to direct at least one stream of liquid into a region adjacent to and underlying said structure lower end whereby said liquid forms a pumpable slurry with the solids in said underlying region and the pump means pumps said last mentioned slurry so that the structure sinks by gravitational action into the volume of the underlying region from which 
     
     
        said slurry is removed..]. 16. Apparatus as in claim .[.15.]. .Iadd.9 .Iaddend.in which .[.said structure includes a caisson.]. .Iadd.the means to move the structure downwardly comprises means to direct at least one stream of liquid into a region adjacent to and underlying said structure lower end whereby said liquid forms a pumpable slurry with solids in said underlying region and the pump means pumps said last mentioned slurry so that the structure sinks by gravitational action into the volume of the underlying region from which said slurry is removed .Iaddend.and said stabilizer means comprises a plurality of circumferentially positioned pilings mounted for movement with the caisson in vertical alignment therewith and having respective lower ends extending below said body upper surface, and the means to move the caisson downwardly includes means to direct a stream of liquid in respective regions adjacent to and underlying said piling lower ends whereby said liquid forms a slurry with the solids in said underlying piling regions whereby said caisson and pilings sink together by gravitational action.  .[.17. Apparatus as in claim 8 in which said sidewall comprises an elongate hollow shell having its longitudinal axis adapted to be disposed vertically in said body of solids, and said means forming the portal opening includes at least one opening in said shell adjacent the caisson lower end..]. .[.18. Apparatus as in claim 17 in which the nozzle means comprises at least one nozzle mounted within said shell to direct a liquid stream outwardly through said portal opening means along a path extending substantially laterally from the caisson to 
     
     
        define said pulping zone..]. 19. Apparatus as in claim 8 in which said portal opening means includes an uppermost opening through which said liquid streams extend, together with means forming a grating positioned below said opening and through which said slurry flows to the pump means, said grating comprising a plurality of vertically extending, laterally 
     
     
        spaced apart bars. 20. Apparatus as in claim 8 in which the means to pump the slurry includes a sump formed in said structure lower end substantially below said portal opening means whereby slurry flows by gravitational action through said portal opening means into said sump and said means to pump said slurry includes an inlet communicating with said sump and an outlet adapted to discharge pumped slurry upwardly through 
     
     
        said structure. 21. Apparatus as in claim 20 wherein said structure forms a substantially water-tight chamber position above said portal opening means, together with pump operating means mounted within said chamber 
     
     
        connected to power said slurry pump means. 22. Apparatus for removing discrete mineral solids from a settled body of the same comprising .Iadd.a caisson.Iaddend., means forming a slurry receiving pump .Iadd.in the caisson.Iaddend., portal means .Iadd.in the caisson .Iaddend.for directing slurry into said sump, pump means for pumping slurry from said sump to a zone remote therefrom, nozzle means mounted above said sump for directing liquid streams laterally into the mineral solids to form a slurry therewith, said nozzle means being supported within a diameter of the path of travel defined by the movement of said .[.sump.]. .Iadd.caisson .Iaddend.through said settled body, means for directing liquid under pressure to said nozzle means, .Iadd.means for rotating the nozzle means with respect to said caisson.Iaddend., means for supporting said .[.sump and nozzle means.]. .Iadd.caisson .Iaddend.at predetermined elevations within said settled body, and means for injecting additional liquid into the mineral solids below said .[.sump.]. .Iadd.caisson .Iaddend.to form additional slurry through which said  .[.sump and nozzle means are.]. 
     
     
        .Iadd.caisson is .Iaddend.caused to sink. 23. Apparatus as in claim 22 in which the support means includes means for progressively lowering said sump and nozzle means while said additional liquid is being injected below said sump for controlling the elevation to which said sump and nozzle 
     
     
        means are lowered through the settled body. 24. Apparatus as in claim 23 in which said portal means is positioned at an elevation below said nozzle means for receiving slurry which is formed by the liquid from the nozzle means. .Iadd. 25. A method of removing a settled body of discrete mineral solids capable of being formed into a pumpable slurry by nozzle means and slurry pump means which are mounted within a housing structure, said structure including a caisson, and said caisson is stabilized by a plurality of pilings positioned circumferentially around said caisson and extending vertically into the body of mineral solids adjacent thereto, including the steps of establishing the nozzle means and slurry pump means in the body with the nozzle means located at a first predetermined elevation below the upper surface of said body, directing at least one stream of liquid from said nozzle means into a path extending substantially laterally therefrom to define a pulping zone whereby the liquid forms a pumpable slurry with solids within said zone, pumping the slurry from the zone with said slurry pump means until solids within the region adjacent said nozzle means are substantially removed, directing additional liquid into a region underlying said structure to form additional pumpable slurry with the mineral solids and pumping the additional slurry away from said underlying region to sink the nozzle means and slurry pump means downwardly to a second region with said nozzle means located at a second predetermined elevation below said first elevation, the step of sinking the nozzle means and slurry pump means including directing liquid into regions adjacent to and underlying said pilings whereby the liquid forms a slurry with the mineral solids therein sufficient to allow the pilings to sink by gravitational action with the caisson through the slurry thus formed, and repeating the steps of directing at least one liquid stream from said nozzle means into a path to define an additional pulping zone and pumping slurry from said additional zone until the solids within said second region are substantially removed. .Iaddend.