Rock Bolt and an Anchoring Device

Abstract

A rock bolt including an elongate shaft, and an anchoring device attached to the shaft having an expansion mechanism. The anchoring device is operable to expand radially relative to the lengthwise extent of the shaft to anchor the rock bolt within a bore drilled into a rock body. The anchoring device includes an annular band, which extends about the expansion mechanism to resist expansion of the mechanism. The band is arranged so it can enter the bore in which the bolt is to be anchored in position about the expansion mechanism and to maintain a resistance to expansion of the expansion mechanism at least until the expansion mechanism has substantially fully entered the bore. The band can be a polymeric material such as a heat shrink polymeric material in tight fitting engagement about the expansion mechanism so as to conform to the external shape of the expansion mechanism.

1 . A rock bolt comprising:
 an elongate shaft, and   an anchoring device attached to the shaft, the anchoring device having an expansion mechanism which is operable to expand radially relative to the lengthwise extent of the shaft to anchor the rock bolt within a bore drilled into a rock body, the anchoring device including an annular band which extends about the expansion mechanism to resist expansion of the mechanism, the band being arranged so it can enter the bore in which the bolt is to be anchored in position about the expansion mechanism and to maintain a resistance to expansion of the expansion mechanism at least until the expansion mechanism has substantially fully entered the bore.   
     
     
         2 . A rock bolt according to  claim 1 , the band being of a polymeric material that is in tight fitting engagement about the expansion mechanism. 
     
     
         3 . A rock bolt according to  claim 2 , the band being of a heat shrink polymeric material in tight fitting engagement about the expansion mechanism so as to conform to the external shape of the expansion mechanism. 
     
     
         4 . A rock bolt according to  claim 1 , the band being of a paper, plastic or fabric adhesive tape, string, or strapping. 
     
     
         5 . An anchoring device according to  claim 1 , wherein the band has a first condition in which it resists expansion of the expansion mechanism, and a second condition in which it at least partially disintegrates to allow the expansion mechanism to expand, the band being formed to take the second condition when the expansion mechanism of the anchoring device fitted to a rock bolt has at least substantially fully entered the bore in which the rock bolt is to be anchored. 
     
     
         6 . A rock bolt according to  claim 1 , wherein the band has an axial length of up to about 125 mm. 
     
     
         7 . A rock bolt according to  claim 1 , the band has an axial length of up to about 100 mm. 
     
     
         8 . A rock bolt according to any one of  claims 1  to  5 , the band has an axial length of up to about 75 mm. 
     
     
         9 . A rock bolt according to  claim 1  wherein the band has an axial length of up to about 50 mm. 
     
     
         10 . A rock bolt according to  claim 1 , Wherein the band comprises at least one pair of bands spaced apart axially. 
     
     
         11 . A rock bolt according to  claim 10 , wherein the at least one pair of bands each have an axial length of up to about 50 mm. 
     
     
         12 . A rock bolt according to  claim 1  wherein the band has a wall thickness of about 1 mm. 
     
     
         13 . A rock bolt according to  claim 1  wherein the band comprises at least a pair of bands in overlapping relationship. 
     
     
         14 . A rock bolt according to a shaft extending between the ends  claim 1 , wherein the shaft extends between a first and a second end, the anchoring device extending along a first part of the shaft adjacent the first end, the expansion mechanism comprising a mandrel, and at least one expansion element overlaying the mandrel, wherein the at least one expansion element is displaced radially outwardly on a predetermined relative movement between the mandrel and the at least one expansion element, wherein the at least one expansion element is joined to a connector to form an anchor assembly, said anchor assembly being keyed to the mandrel, and said anchor assembly comprising relative rotation actuator means active during rotation of the anchoring device. 
     
     
         15 . A rock bolt according to  claim 1  wherein the rock bolt is a self drilling rock bolt. 
     
     
         16 . An anchoring device for a rock bolt comprising:
 an elongate shaft;   an expansion mechanism which is operable to expand radially relative to the lengthwise extent of the rock bolt shaft to anchor the rock bolt within a bore drilled into a rock body; and   an annular band extending about the expansion mechanism to resist expansion of the mechanism, the band being arranged so that it can enter the bore in which the bolt is to be anchored in position about the expansion mechanism and to maintain a resistance to expansion of the expansion mechanism at least until the expansion mechanism has substantially fully entered the bore.   
     
     
         17 . An anchoring device according to  claim 16 , wherein the band is a polymeric material that is in tight fitting engagement about the expansion mechanism. 
     
     
         18 . An anchoring device according to  claim 17 , wherein the band is a heat shrink polymeric material that is in tight fitting engagement about the expansion mechanism so as to conform to the external shape of the expansion mechanism. 
     
     
         19 . An anchoring device according to  claim 16 , wherein the band is a paper, plastic or fabric adhesive tape, string, or strapping. 
     
     
         20 . An anchoring device according to  claim 16 , wherein the band has a first condition in which it resists expansion of the expansion mechanism, and a second condition in which it at least partially disintegrates to allow the expansion mechanism to expand, the band being formed to take the second condition when the expansion mechanism of the anchoring device fitted to a rock bolt has at least substantially entered the bore in which the rock bolt is to be anchored. 
     
     
         21 . An anchoring device according to  claim 20 , wherein the band is formed to take the second condition by frictional rubbing of the band against a facing surface of a bore into which the rock bolt is installed. 
     
     
         22 . A method of installing a rock bolt, the rock bolt comprising an elongate shaft, and an anchoring device attached to the shaft and having an expansion mechanism which is operable to expand radially relative to the lengthwise extent of the shaft to anchor the rock bolt within a bore drilled into a rock body, the anchoring device including an annular band which extends about the expansion mechanism to resist expansion of the mechanism, the band being arranged to enter the bore in which the bolt is to be anchored in position about the expansion mechanism and to maintain a resistance to expansion of the expansion mechanism at least until the expansion mechanism has substantially fully entered the bore, the method comprising the steps of:
 drilling a bore into a rock body to the desired depth of penetration into the rock body;   inserting the rock bolt; and   expanding the expansion mechanism.   
     
     
         23 . A method of installing a rock bolt according to  claim 22 , wherein the band is a polymeric material that is in tight fitting engagement about the expansion mechanism. 
     
     
         24 . A method of installing a rock bolt according to  claim 23 , wherein the band is a heat shrink polymeric material in tight fitting engagement about the expansion mechanism. 
     
     
         25 . A method of installing a rock bolt according to  claim 22  wherein the band is a paper, plastic or fabric adhesive tape, string, or strapping. 
     
     
         26 . The method of, according to  claim 22 , wherein the rock bolt is a self drilling rock bolt so that the method steps of drilling a bore into a rock body and inserting the rock bolt into the bore are conducted simultaneously as the self drilling rock bolt drills the bore.