Dynamic rock stabilizing fixture

Abstract

.[.Anchor fixture for dynamically stabilizing rock structure comprising a rock support mounted in a bore hole and cooperating with formable means placed in the bore hole to generate tension in the support and to exert compression in the rock structure for dynamically supporting the rock structure upon insertion of the rock support and rapidly developing radial loading forces in the rock and beyond the near boundary of the bore hole..]. .Iadd.Dynamic rock stabilization apparatus in the form of an anchor fixture for use with a roof plate in which the fixture has an anchor rod formed with a surface configuration extending from a lead-in end to the opposite headed end for at least a part of the length of the rod, and a hollow body providing a wall of formable and compressible material having a length less than the depth of a bore hole in the rock structure into which it is to be placed between the rod and the surface of the bore hole, the body engaging the surface configuration of the rod to effect a locking engagement with the rod such that when assembled in a bore hole the body wall has a thickness sufficient to be compressed between the rod surface configuration which has a diameter less than the bore hole and the bore hole surface, and to apply dynamic forces through the rock as a result of the compressibility of the body. The invention includes a method of effecting dynamic rock stabilization by placing a body of formable material in a bore hole and inserting an anchor rod into the body so it engages the body and initiates a cooperative reaction between the bore hole and the rod to stabilize the rock structure..Iaddend.

What is claimed is: 
     
       1. An anchor fixture for stabilizing geologic structure exposed in forming a mine passage in a geologic structure for recovery of material in such geologic structure, the exposed geologic structure having a bore hole of predetermined diameter to receive the anchor fixture, said anchor fixture comprising: (a) an elongated body of formable plastic material in the shape of a tube having opposite edges that overlap to present a continuous circumferential wall to the circumferential surface in the bore hole opening, the tube wall having a thickness of the order of substantially 0.0625 to 0.125 inches;   (b) an elongated rod received in said body of formable plastic material, said rod having a raised surface along its length in the form of a buttress thread having a flattened crest and with the buttress face directed toward the mine passage to place said formable plastic material in full circumferential contact with the bore hole under load to exert a continuing supporting thrust by the formable plastic material between the bore hole circumferential surface and the buttress thread for establishing a dynamic system of vector forces radiating into the geologic structure;   (c) said elongated rod having a diameter as measured from the flattened crest of the buttress thread less than the diameter of the bore hole, and said body of formable plastic material having a wall thickness greater than the annular space between the bore hole surface and the flattened crest of said buttress thread, and said body of formable material being forced by insertion friction of said rod to flow into the buttress thread to assume the shape of the buttress thread on the inner surface of the formable plastic material and to react following rod insertion in compression between the flattened crest and root of the buttress thread and the surface of the bore hole for creating loading forces radiating into the geologic structure beyond the boundary immediately adjacent the bore hole;   (d) a rigid structure support plate engaged on said rod and held thereby directly against the exposed geologic structure surrounding the bore hole, the engagement of the structural support plate against the exposed geologic structure reacting on said rod to exert axial tension in said rod and compression of the formable plastic material through the buttress face of the buttress thread such that a substantially continuous dynamic spiral wedge is created along the bore hole surface for supporting the geologic structure with a dynamic support pattern surrounding the bore hole adjacent the exposed structure and locking said rod in the bore hole with said rigid structural support plate in position to oppose the tendency of the geologic structure to move.   
     
     
       2. An anchor fixture for stabilizing geologic structure exposed in forming a mine passage, the exposed structure having a bore hole of predetermined diameter to receive the anchor fixture, said anchor fixture comprising: (a) a body of formable plastic material in the shape of an elongated tube with opposite elongated edges in overlapping positions to present a continuous surface with a circumferential dimension that fits the circumference of the bore hole, said tube having a wall thickness of the order of substantially 0.0625 to 0.125 inches;   (b) an elongated rod having a preformed surface configuration thrusted into said tubular shaped body, said surface presented to said tubular shaped body generating friction heat for causing said plastic material to flow and generally conform to said surface configuration on its inside and outside surfaces for creating a dynamic system of vector forces around the circumference of the bore hole; and   (c) a rigid support plate engaged on said rod and retained in contact by said rod against the surface of the exposed mine passage, said support plate placing said rod in axial tension so that the dynamic system of vector forces around the circumference of the bore hole are maintained by said plastic material and substantially match the surface configuration of said rod.   
     
     
       3. The anchor fixture set forth in claim 2 wherein said tubular shaped body has a wall thickness such that its volume is greater than the volume of the annular space between said rod and the bore hole surface. 
     
     
       4. The anchor fixture set forth in claim 2 wherein said plastic material has a thickness of the order of from about 0.0625 to about 0.125 inches and up to a thickness of as much as one-hundred percent greater than the radial dimension of the annular space between the rod and the surface of the bore hole. 
     
     
       5. The anchor fixture set forth in claim 2 wherein said preformed surface of said rod is a buttress thread having a flattened crest and positioned with the buttress face directed toward the mine passage, said buttress thread having a diameter at said thread crest of about fifteen-sixteenth inch and a diameter at the thread root of about three-fourth inch such that the annular space around said rod relative to the bore hole diameter is about one-thirty second of an inch, and said vector forces are variable being greater in the area of said flattened crest than in the area of said thread root. .Iadd. 
     
     
       6.  An anchor fixture for use with a roof plate for stabilizing geologic structure which has a bore hole of a predetermined diameter and length from a closed end formed therein to an open end, said anchor fixture apparatus comprising: (a) an elongated rod that is at least substantially the length of said bore hole from a lead-in end of the rod to an opposite driven end, said rod having a diameter that is less than the predetermined diameter of said bore hole, 1. said elongated rod having an uneven surface formed thereon extending from said lead-in end thereof toward the opposite driven end over at least a portion of its length which is less than the length of said rod and less than the length of the bore hole; and     (b) a body of compressible plastic material, having a length, from adjacent the closed end of the bore hole, less than the length of the bore hole and adapted to be formed into a tubular shape having an initial diameter and flexibility to permit the tubular shape to expand and conform to the bore hole surface and the uneven surface of said rod upon interpositioning of said body between said uneven surface of said rod and said bore hole spaced from the open end thereof whereby said compressible plastic material responds dynamically to the presence of said rod in the bore hole, 1. to effect a locking engagement of said uneven surface of said lead-in end of said rod with said body, thereby to fasten said rod in said bore hole from said lead-in end, and   2. to transmit thrust forces from the uneven surface of the rod into the geologic structure of the bore hole through said body. .Iaddend. .Iadd.7. An anchor fixture apparatus for use with a roof plate for stabilizing a geologic structure which has a bore hole of a predetermined diameter along its depth from a closed end to an open end, said anchor fixture apparatus comprising:     (a) an elongated rod at least as long as the bore hole depth between the open and closed ends and having a lead-in end, an opposite driven end, and a surface configuration on said rod extending from said lead-in end along a predetermined portion of the length of said rod as measured from the lead-end which is less than the length of said rod and has a diameter that is of the order of approximately one-sixteenth inch smaller than the predetermined bore hole diameter such that said rod surface configuration has a loose fit relative to the bore hole; and   (b) an elongated body of a formable and compressible material positionable adjacent the closed end of the bore hole and having a length less than the bore hole depth, and said body having an initial tubular shape for reception in the bore hole and being yieldable to split under compression and expand radially outwardly in the bore hole for receiving said elongated rod, said body of formable and compressible material being compressed by said rod surface configuration, and said formable and compressible material responding dynamically to the presence of said rod in the bore hole,   
     
     
       1.  to effect a compression locking engagement along the length of said surface configuration on said rod within said body thereby to secure said surface configuration on said rod in the bore hole, and 2. to apply thrust forces through said body along the length of the engagement of said rod and body into the geologic structure. .Iaddend. .Iadd.8. An anchor fixture for dynamically stabilizing geologic structure having a bore hole drilled to a predetermined diameter and depth to receive the anchor fixture and extending to a closed end in the geologic structure from an anchor fixture receiving open end, said anchor fixture comprising:   (a) an elongated rod having a length from a lead-in end to an opposite driven end adjacent the open end of the bore hole and a surface configuration extending along a portion of the rod less than the length of said rod from the lead-in end thereof, the diameter of which surface configuration portion is less than the bore hole diameter, such that an annular space is created whereby the surface configuration portion of said rod has a loose fit in the bore hole,   (b) an elongated body of compressible and formable material adapted to be passed into the bore hole so as to be positioned adjacent the closed end of the bore hole and have a length less than the depth of the bore hole and extending along the bore hole from adjacent the closed end thereof, said body being responsive under compression by said rod to split and gap while occupying a position adjacent said rod from said lead-in end and so as to present a wall between said surface configuration on said rod and the adjacent bore hole, said body wall having a thickness to exceed the dimension of the annular space that allows for the loose fit of said rod in the bore hole, whereby said rod forces said body to radially expand against the bore hole surface for effecting a locking engagement of said rod surface configuration within said body and for transmitting thrust forces through said body into the bore hole and the adjacent geologic structure and   (c) a thrust plate held by said rod against the geologic structure surrounding the anchor fixture receiving end of the bore hole, said thrust plate loading said rod in tension whereby said body reacts between said rod and the bore hole surface for dynamically stabilizing the geologic   
     
     
        structure surrounding the bore hole. .Iaddend. .Iadd.9.  The anchor fixture according to claim 8 wherein said elongated body of formable material is initially in the form of a sheet presenting an external circumferential surface engaged with the bore hole, and said elongated rod upon being inserted in said body of formable material acts to compress said body between the surface configuration of said rod and the bore hole surface for developing substantially immediate shear strength under compression of said body of formable material. .Iadd.10. The anchor fixture according to claim 8 wherein the wall thickness of said elongated body of formable material may be selected to fall into a range of from a minimum of about one-sixteenth inch to a maximum of as much as one-hundred percent greater than the radial dimension of said annular space between said surface configuration on said rod of formable material and the bore hole surface. .Iaddend. .Iadd.11. An anchor fixture for maintaining dynamic support and stabilizing forces in a geologic structure having a bore hole drilled to a predetermined depth and diameter, the anchor fixture being mounted in that bore hole adjacent the closed end thereof, said anchor fixture comprising: (a) an elongated rod having a lead-in end and a driven end and a thread on at least a portion of the length of its surface that is less than the rod length as measured from adjacent a lead-in end, the thread having a rounded crest with a buttress face directed toward the driven end of said rod upon insertion of the rod into the bore hole, and the thread crests having a diameter that is less than the bore hole diameter thereby leaving an annular space between the bore hole and the thread crests;   (b) an elongated body of compressible and formable material positioned adjacent the closed end of the bore hole and having a length less than the depth of the bore hole for anchoring said threaded portion of said elongated rod in the bore hole adjacent the closed end of said bore hole, said body of formable material having a length less than the depth of the bore hole and having a wall thickness which substantially fills the volume of the annular space between the bore hole and said threads on said rod such that the rod threads are imprinted in said material and in turn the formable material is forced to flow into the threads and is compressed against the surface of the bore hole adjacent the closed end thereof for initiating a condition of dynamic support through the bore hole surface and into the geologic structure through said rod exerting thrust forces into the geologic structure along the length of the engagement of the rod threads in the body of formable material; and   (c) a load bearing plate engaged on said rod and retained against the geologic structure by the rod engaged in said formable material, said rod being forced into said bore hole so as to be loaded in tension by said plate being retained against the geologic structure for maintaining the condition of dynamic support of the geologic structure and thrust forces radiating into the geologic structure surrounding the bore hole. .Iaddend.   
     
     
        .Iadd.12.  The anchor fixture according to claim 11 wherein said body of formable material and said rod generates body of formable material in a state of dynamic support of the geologic structure, and said formable material is yieldable laterally so that the occurrence of shift in the geologic structure laterally relative to said rod continues the dynamic support of the geologic structure and anchorage along the length of said formable body. .Iaddend. .Iadd.13. The anchor fixture according to claim 11 wherein the thrust forces adjacent said thread crest are large compared with thrust forces adjacent the root of the threads to produce a variable spiral loading through the formable material upon the geologic structure. 
     
     
        .Iaddend. .Iadd.14.  A method of dynamically supporting and stabilizing the geologic structure adjacent a bore hole in such structure, the method comprising the steps of: (a) forming a closed end bore hole of a predetermined diameter and depth to a closed end in the geologic structure from an open end in an exposed surface thereof;   (b) providing an elongated rod having a lead-in end with a surface configuration along a portion of the rod lead-in end less than the length of the elongated rod, and which has a diameter that is less than the predetermined diameter of the bore hole such that there remains an annular space between the bore hole and the surface configuration portion of the rod;   (c) selecting a body of formable material having a wall with a thickness greater than the difference between the predetermined diameter of the bore hole and the diameter of the surface configuration portion of said rod;   (d) forming that body of formable material into a tubular configuration that has a length less than the depth of the bore hole as measured from the closed end in such geologic structure;   (e) assembling the tubular body of the formable material and the elongated rod in the bore hole such that the tubular body is compressed radially outwardly against the surface of the bore hole by the surface configuration portion on said elongated rod such that the elongated rod is anchored through the length of the formable material compressed by the length of the surface configuration on said rod adjacent the lead-in end thereof to create dynamic support and stability of the geologic structure; and   (f) providing a load bearing plate on the elongated rod to contact the exposed surface of the geologic structure thereby exerting tension on the elongated rod and maintaining the tubular body in a state of compression for continuing the dynamic support of the geologic structure. .Iaddend.   
     
     
        .Iadd.15.  A method according to claim 14 wherein the step of assembling the tubular body and the elongated rod causes the formable material of the tubular body to flow into and substantially fill the surface configuration on the rod. .Iaddend. .Iadd.16. A method according to claim 14 wherein the step of selecting the rod of a given diameter and the thickness of the formable material is such that there is created a condition where the rod is substantially locked in the bore hole. .Iaddend. .Iadd.17. A method according to claim 14 wherein the step of forming the configuration on the elongated rod extends over a length thereof substantially equal to the length of the body of formable material. .Iaddend.