Rock bolt with an integrally formed wedge formation and a method of manufacturing same

Abstract

The invention provides an end anchored rock bolt 20 which includes an elongate cylindrical body 12 which longitudinally extends between a proximal end and a distal end and a plug 18 at the distal end, which plug is diametrically larger than the cylindrical body 12, is at least partially tapered, tapering towards the proximal end, and is integrally formed on the body 12.

1 . An end anchored rock bolt which includes an elongate cylindrical body which longitudinally extends between a proximal end and a distal end and a plug at the distal end, which plug is diametrically larger than the cylindrical body, is at least partially tapered, tapering towards the proximal end, and is integrally formed on the body. 
     
     
         2 . An end anchored rock bolt according to  claim 1  which includes a radially expansible shell which engages with the body, positioned thereon to radially expand when the plug or the shell is caused to move towards the other. 
     
     
         3 . An end anchored rock bolt according to  claim 2  wherein the radially expansible shell is biased into abutment with the plug. 
     
     
         4 . An end anchored rock bolt according to  claim 3  wherein the radially expansible shell comprises a plurality of radially arranged interlinked leaves. 
     
     
         5 . An end anchored rock bolt according to  claim 1  wherein the plug has an angle of taper in the range 6° to 12°. 
     
     
         6 . An end anchored rock bolt according to  claim 5  wherein the angle is 9°. 
     
     
         7 . An end anchored rock bolt which includes an elongate cylindrical body which longitudinally extends between a proximal end and a distal end and a plug at the distal end and a mechanical anchor, wherein the anchor includes a plug which is integrally formed on the body at the distal end and which is at least partially tapered, tapering towards the proximal end, and a radially expansible shell which engages with the body and is biased into abutment with the plug to radially expand when the plug or the shell is caused to move towards the other. 
     
     
         8 . A method of manufacturing an end anchored rock bolt, the method including the steps of:
 a) providing an elongate rod of a steel material which longitudinally extends between a distal end and a proximal end; and   b) forming a plug at the distal end of the rod to be diametrically larger than the rod and at least partially tapered, tapering towards the proximal end.   
     
     
         9 . A method according to  claim 8  wherein the plug is formed in a forging process. 
     
     
         10 . A method according to  claim 9  wherein the forging process includes at least one upsetting step, wherein the distal end of the rod is placed in a first one die and a force is directed down the rod so as to cause the distal end of the rod to conform to the shape of the die. 
     
     
         11 . A method according to  claim 10  wherein the forging process includes a first upsetting step, wherein the distal end of the rod is placed in the first die, and a second upsetting step wherein the distal end is placed in a second die, and wherein, in each step a force is directed down the rod so as to cause the distal end to conform to the shape of the first die and the second die respectively. 
     
     
         12 . A method according to  claim 10  wherein the forging process includes a step, preceding the upsetting step or steps of preheating the distal end of the rod before placing it in the respective die. 
     
     
         13 . A method according to  claim 12  wherein the distal end of the rod is preheated to a temperature above the recrystallization temperature of the steel material.