Rock bolt

Abstract

A rock bolt which includes a tubular member made from aluminium which is at a fixed position inside or outside a borehole, a cable which goes through the tubular member, and a steel barrel, secured to the cable which deforms the tubular member to give a yielding action with rock movement.

1 . A rock bolt which includes an elongate member, a tube which is made from a first material and which has a bore, an inner surface opposing the bore and an outer surface, and a barrel which is fixed to the elongate member and which is located at least partly in the bore, wherein the barrel is made from a second material which is harder than the first material and includes yield formations, configured to engage with the inner surface of the tube and to deform the first material in response to a tensile force exerted on the elongate member which forces the barrel further into the bore. 
     
     
         2 . A rock bolt according to  claim 1  wherein the tube has a first end and a second end, and the barrel enters the bore of the tube at the first end and the elongate member extends from the second end of the tube. 
     
     
         3 . A rock bolt according to  claim 1  which includes an anchor for engaging with a wall of a borehole and wherein the tube and the barrel are in use positioned outside the borehole. 
     
     
         4 . A rock bolt according to  claim 1  which includes an anchor for engaging with a wall of a borehole and wherein the tube and the barrel are in use positioned inside the borehole. 
     
     
         5 . A rock bolt according to  claim 1  which includes an anchor which in use is located inside a borehole into which the elongate member extends and which fixes the elongate member to the wall of the borehole, or which fixes the tube to the wall of the borehole. 
     
     
         6 . A rock bolt according to  claim 1  wherein the first material is aluminum and the second material is steel. 
     
     
         7 . A rock bolt according to  claim 1  wherein the yield formations comprise ribs on a surface of the barrel which opposes the inner surface of the tube and a respective valley is formed between each adjacent pair of the ribs. 
     
     
         8 . A rock bolt according to  claim 7  wherein the ribs are tapered, in a radial sense, moving away from an end of the elongate member to which the barrel is fixed. 
     
     
         9 . A rock bolt according to  claim 7  wherein a thickness of the tube between the outer surface and the inner surface is such that when the first material is deformed, the formations on the barrel extend into the tube, from the inner surface, but do not extend to the outer surface. 
     
     
         10 . A rock bolt according to  claim 2  wherein the first material is aluminum and the second material is steel. 
     
     
         11 . A rock bolt according to  claim 3  wherein the first material is aluminum and the second material is steel. 
     
     
         12 . A rock bolt according to  claim 4  wherein the first material is aluminum and the second material is steel.