Resin Groutable Expansion Anchor and Method of Installing Same

Abstract

A rock bolt and a method of installing a rock bolt in a borehole ( 3 ) of a rock formation. The rock bolt including an elongate shank ( 1 ) and an expansion assembly ( 2 ) located at the distal end of the shank. The expansion assembly being expandable to lock the rock bolt in a borehole upon relative forward rotation of the rock bolt. The rock bolt further including stop means ( 4 ) to lock the expansion assembly with respect to the rock bolt for conjoined rotation upon a reverse rotation of the rock bolt.

1 . A rock bolt having:
 an elongate shank;   an expansion assembly at the distal end of said shank, said expansion assembly being expandable to lock said rock bolt in a borehole upon relative forward rotation of said rock bolt; and   stop means to lock said expansion assembly with respect to said rock bolt for conjoined rotation upon a reverse rotation of said rock bolt.   
     
     
         2 . A rock bolt according to  claim 1 , wherein said expansion assembly includes an expansion shell having two or more longitudinally extending elongate expansion leaves for locking said rock bolt in said borehole. 
     
     
         3 . A rock bolt according to  claim 2 , wherein said expansion shell is slidably engaged with said shank and is supported on said shank by an abutment member. 
     
     
         4 . A rock bolt according to  claim 3 , wherein said abutment member is a nut threadedly engaged with said shank. 
     
     
         5 . A rock bolt according to any one of  claims 2  to  4 , wherein the diameter of said expansion shell is substantially equal to the diameter of said rock bolt shank such that said cementing material flows more freely to the region of said rock bolt shank below said expansion shell. 
     
     
         6 . A rock bolt according to any one of  claims 2  to  5 , wherein said expansion assembly includes a chuck in threaded engagement with said shank such that rotation of said rock bolt with respect to said chuck causes axial movement of said chuck, said chuck having surfaces in sliding keying engagement with complementary surfaces on said expansion leaves to cause outward divergent deformation of said leaves upon said relative forward rotation of said rock bolt. 
     
     
         7 . A rock bolt according to  claim 6 , wherein said chuck and expansion shell are adapted for conjoined rotation. 
     
     
         8 . A rock bolt according to any one of the preceding claims, wherein said stop means is a stop formation disposed at the distal end of said rock bolt shank. 
     
     
         9 . A rock bolt according to  claim 8 , wherein said stop formation is a flange member fixedly connected to said rock bolt shank. 
     
     
         10 . A rock bolt according to  claim 8 , wherein said stop formation is formed from a portion of said rock bolt shank. 
     
     
         11 . A rock bolt according to  claim 10 , wherein the distal end of said rock bolt is pressed flat to define said stop formation. 
     
     
         12 . A rock bolt according to any one of  claims 2  to  11 , wherein each leaf includes a plurality of gripping formations disposed on its outer surface for gripping engagement with said borehole. 
     
     
         13 . A rock bolt according to any one of  claims 6  to  12 , wherein said chuck surfaces are tapered. 
     
     
         14 . A rock bolt according to any one of  claims 6  to  13 , wherein said chuck includes one or more fluid flow passageways. 
     
     
         15 . A rock bolt substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples. 
     
     
         16 . A method of installing a rock bolt according to any one of  claims 1  to  15  in a borehole of a rock formation, including the steps of:
 (i) inserting a frangible capsule containing a cementing material into the borehole;   (ii) inserting the rock bolt into the borehole until the capsule is ruptured and rotating in a reverse direction whilst applying an insertion force to further insert into the borehole; and   (iii) rotating the bolt in a forward direction to expand the expansion assembly and thereby lock the rock bolt in the borehole.   
     
     
         17 . A method according to  claims 16 , wherein a substantial portion of said rock bolt shank is encapsulated by said cementing material after step (ii). 
     
     
         18 . A method according to  claim 16  or  claim 17 , wherein said reverse rotation mixes said cementing material. 
     
     
         19 . A method according to any one of  claims 16  to  18 , wherein said frangible capsule in substantially shredded by said reverse rotation. 
     
     
         20 . A method according to any one of  claims 16  to  19 , wherein the head of said rock bolt is substantially 50 mm away from the surface of said rock formation after step (ii). 
     
     
         21 . A method according to any one of  claims 16  to  20 , wherein said cementing material is a two-part epoxy resin compound. 
     
     
         22 . A method of installing a rock bolt substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples.