Anchor bolt with anti projection mechanism

Abstract

An anchor bolt for fastening an object in a drilled borehole in a rock mass formation, which is to absorb violent impact loads such as those occurring during earthquakes in an energy dissipating manner. The anchor bolt comprises a split sleeve and a bolt component inserted in the split sleeve that, when pulled outwardly, expends the split sleeve until a key protruding from the surface of the bolt component abuts a ring, thereby informing the operator that appropriate anchoring and pre-tensioning of the anchor bolt in the borehole is reached. Another ring, interfacing with the split sleeve about the entry of the borehole, is designed to force expansion of the split sleeve, preventing a breaking anchor bolt to become a high-speed projectile.

1 . A hybrid bolt designed to be inserted in a borehole having a borehole wall, the hybrid bolt comprising:
 a sleeve having a first sleeve-end and an expandable second sleeve-end featuring a longitudinal slit; and   a peg having a first peg-end and a second peg-end wherein the peg has a diameter increasing toward the second peg-end thereby providing a frustoconical surface about the second peg-end,   wherein the peg is inserted in the sleeve with the first peg-end opposed to the second sleeve-end, and   wherein the hybrid bolt, when the peg is pulled towards the first sleeve-end, has the frustoconical surface pushing outwards the second sleeve-end which becomes thereby wedged between the frustoconical surface and the borehole wall.   
     
     
         2 . The hybrid bolt of  claim 1 , further comprising a wedge ring inserted between the peg and the sleeve at the second sleeve-end, wherein pulling the peg towards the first sleeve-end wedges the wedge ring between the peg and the sleeve. 
     
     
         3 . The hybrid bolt of  claim 2 , wherein the wedge ring comprises a longitudinal groove parallel to the slit of the sleeve. 
     
     
         4 . The hybrid bolt of  claim 2 , wherein the wedge ring comprises an outwardly extending lip adapted to abut against the second sleeve-end when the peg is pulled towards the first sleeve-end. 
     
     
         5 . The hybrid bolt of  claim 2 , wherein the wedge ring comprises a longitudinal body extending within the sleeve, the longitudinal body having a variable thickness increasing towards the first sleeve-end. 
     
     
         6 . The hybrid bolt of  claim 1 , wherein the sleeve has an external diameter decreasing towards the second sleeve-end. 
     
     
         7 . The hybrid bolt of  claim 1 , wherein the slit is extending from the first sleeve-end to the second sleeve-end. 
     
     
         8 . The hybrid bolt of  claim 7 , wherein the slit narrows towards the second sleeve-end. 
     
     
         9 . The hybrid bolt of  claim 1 , wherein the sleeve comprises a key groove. 
     
     
         10 . The hybrid bolt of  claim 9 , wherein the key groove extends from the first sleeve-end, and the peg comprises a body and a key protruding from the body, wherein the key is adapted to take place in the key groove. 
     
     
         11 . The hybrid bolt of  claim 10 , further comprising an abutting ring slidingly mounted to the first sleeve-end. 
     
     
         12 . The hybrid bolt of  claim 11 , wherein the abutting ring comprises a slit. 
     
     
         13 . The hybrid bolt of  claim 12 , wherein the key has a key-width transversal to the peg, and the slit of the abutting ring has a slit-width transversal to the peg narrower than the key-width. 
     
     
         14 . The hybrid bolt of  claim 11 , wherein the abutting ring is adapted to slide into the sleeve. 
     
     
         15 . The hybrid bolt of  claim 10 , wherein the peg comprises a weakness between the first peg-end and the second peg-end, wherein the weakness induces a foreseeable location for a breaking point to the peg. 
     
     
         16 . The hybrid bolt of  claim 15 , wherein the weakness consists in one of a hole, of a shaving, of a groove, and of threading. 
     
     
         17 . The hybrid bolt of  claim 15 , wherein the weakness is located between the key and the second peg-end. 
     
     
         18 . The hybrid bolt of  claim 1 , wherein the peg comprises a threaded portion extending from the first peg-end towards the second peg-end over a partial length of the peg. 
     
     
         19 . The hybrid bolt of  claim 1 , wherein the peg comprises a body, and a key protruding from the body, and a threaded portion extending between the first peg-end and the key. 
     
     
         20 . The hybrid bolt of  claim 11 , further comprising a mounting nut adapted to be mounted to the peg, the mounted nut adapted to butt off against the abutting ring, pushing the abutting ring inside the sleeve.