Rock Bolting Method and Rock Bolt

Abstract

A method for providing a rock bolt ( 2 ) for rock bolting, wherein a rock bolt ( 2 ) having a tubular bolt portion ( 4 ) with a closed cross section is inserted and expanded for bearing contact in a bore hole ( 3 ) in a rock structure ( 1 ). The length of the tubular bolt portion ( 4 ) is determined such that maximum frictional force at pulling inside a bore hole ( 3 ) of a rock bolt with a tubular bolt portion with this length is below a predetermined maximum value. The invention also concerns a rock bolt.

1 . Method for providing a rock bolt ( 2 ) for rock bolting, wherein a rock bolt ( 2 ) having a tubular bolt portion ( 4 ) with a closed cross section is inserted and expanded for bearing contact in a bore hole ( 3 ) in a rock structure ( 1 ), characterized in 
 that the length of the tubular bolt portion ( 4 ) is determined such that maximum frictional force at pulling inside a bore hole ( 3 ) of a rock bolt with a tubular bolt portion with this length is below a predetermined maximum value.    
   
   
       2 . Method according to  claim 1 , charactrized in 
 that the length of the tubular bolt portion ( 4 ) is determined starting out from a measurement or measurements preformed at pulling of at least one rock bolt ( 10 ) with a tubular bolt portion ( 11 ) of predetermined length in a bore hole ( 12 ) in the same or in a corresponding rock structure.    
   
   
       3 . Method according to  claim 1 , characterized in 
 that said predetermined value is the yield point load of the tubular bolt portion.    
   
   
       4 . Method as claimed in  claim 3 , characterized in 
 that the length is set such that said maximum calculated frictional force is set to about 60-about 90% of said yield point load.    
   
   
       5 . Method according to  claim 1 , characterized in 
 that said length is determined such that minimal frictional force in a bore hole of the rock bolt ( 2 ) with a tubular bolt portion ( 4 ) with this length exceeds a predetermined minimum value.    
   
   
       6 . Rock bolt ( 2 ) including a tubular bolt portion ( 4 ) with a closed cross section for insertion and expansion for bearing contact in a bore hole ( 3 ), characterized in 
 that the length of the tubular bolt portion ( 4 ) is dimensioned such that maximal frictional force when pulling inside a bore hole of a rock bolt with a tubular bolt portion with this length, is below a predetermined maximum value.    
   
   
       7 . Rock bolt according to  claim 6 , characterized in 
 that the length of the tubular bolt portion ( 4 ) is determined starting out from at least one measurement preformed when pulling of at least one rock bolt having a tubular bolt portion of a determined length in a bore hole in the same or in a corresponding rock structure.    
   
   
       8 . Rock bolt according to  claim 6 , characterized in 
 that said predetermined value is the yield point load of the tubular bolt portion.    
   
   
       9 . Rock bolt according to  claim 8 , characterized in 
 that the length is dimensioned such that the said maximum frictional force comprises about 60-about 90% of said yield point load.    
   
   
       10 . Rock bolt according to  claim 6 , characterized in 
 that said length is dimensioned such that minimal frictional force inside a bore hole for a rock bolt ( 2 ) with a tubular bolt portion ( 4 ) of this length exceeds a predetermined minimum value.    
   
   
       11 . Method according to  claim 2 , characterized in that said predetermined value is the yield point load of the tubular bolt portion.  
   
   
       12 . Method according to  claim 11 , characterized in that the length is set such that said maximum calculated frictional force is set to about 60-about 90% of said yield point load.  
   
   
       13 . Method according to  claim 2 , characterized in that said length is determined such that minimal frictional force in a bore hole of the rock bolt ( 2 ) with a tubular bolt portion ( 4 ) with this length exceeds a predetermined minimum value.  
   
   
       14 . Method according to  claim 3 , characterized in that said length is determined such that minimal frictional force in a bore hole of the rock bolt ( 2 ) with a tubular bolt portion ( 4 ) with this length exceeds a predetermined minimum value.  
   
   
       15 . Method according to  claim 4 , characterized in that said length is determined such that minimal frictional force in a bore hole of the rock bolt ( 2 ) with a tubular bolt portion ( 4 ) with this length exceeds a predetermined minimum value.  
   
   
       16 . Rock bolt according to  claim 7 , characterized in that said predetermined value is the yield point load of the tubular bolt portion.  
   
   
       17 . Rock bolt according to  claim 16 , characterized in that the length is dimensioned such that the said maximum frictional force comprises about 60-about 90% of said yield point load.  
   
   
       18 . Rock bolt according to  claim 7 , characterized in that said length is dimensioned such that minimal frictional force inside a bore hole for a rock bolt ( 2 ) with a tubular bolt portion ( 4 ) of this length exceeds a predetermined minimum value.  
   
   
       19 . Rock bolt according to  claim 8 , characterized in that said length is dimensioned such that minimal frictional force inside a bore hole for a rock bolt ( 2 ) with a tubular bolt portion ( 4 ) of this length exceeds a predetermined minimum value.  
   
   
       20 . Rock bolt according to  claim 9 , characterized in that said length is dimensioned such that minimal frictional force inside a bore hole for a rock bolt ( 2 ) with a tubular bolt portion ( 4 ) of this length exceeds a predetermined minimum value.