Abstract:
The commonly used resin is an important medium for realizing the bonding between rebar bolt and surrounding rock,and its work performance has an important influence on anchoring quality. The key step of anchoring is to stir the resin with the end of bolt. In order to clarify the problem of mixing resin at the end of threaded steel bolt,based on the existing results,the types of the mixing end of rebar bolt are analyzed,and the mechanical analysis of the double-wedge-shaped end mixing resin is carried out. The theoretical basis for the good effect of adding V\" groove double wedge-shaped stirring end is obtained. The V\"-shaped groove added to the end of bolt helps the end of bolt to pierce the resin sealing bag,increasing the rotation force of resin,better destroying the resin bag,and enhancing the mixing effect of resin. Experiments have found that the cutting angle is in the range of 60°-75°,and the pull-out force of bolt has a gradually increasing trend with the increase of cutting angle. When the rebar bolt with V\" grooves are added to the double wedge-shaped ends,the average pull-out force peak is 22% higher than that without V\" grooves and 62% higher than the traditional prototype bolts. Compared with the double-wedge-shaped mixing end of bolt with transverse ribs,the average pull-out force peak of the double-wedge-shaped mixing end of bolt without transverse ribs has been reduced by about 16%. By observing the mixing process through the high-speed dynamic non-contact full-field strain test system,it was found that the mixing end of traditional bolt is mixed resin,resin bag is squeezed and frictionally damaged by the mixing end,and no twist occurred during the destruction of resin bag. The single-wedge-shaped mixing end of bolt is inserted into the gap between the resin and the borehole wall when the resin is mixed,and the resin is pushed into one side of the borehole wall to squeeze and rotate,and the bag is broken from the side of the resin. When the double-wedge-shaped mixing end of bolt mixes the resin,the double-wedge-shaped end of bolt causes the top of resin bag to be dented,squeezed and twisted. Finally the resin bag is destroyed. The V\" groove is cut at the double-wedge-shaped end of bolt,which makes resin bag more twisted,and is more helpful to destroy resin bag,so that resin can be mixed more fully and the mixing efficiency of resin can be improved.