Investigation of rock bolting for deeply buried tunnels via a new efficient hybrid DEM-Analytical model

The reinforcement mechanism of fully grouted passive rock bolting and the effect of supporting parameters are analyzed by the proposed hybrid model. Some useful numerical results are presented. It is found that rock bolts prevent the breakage of particle bonds immediately around them, and two transmission patterns of bond forces are observed in the nearby areas of rock bolts. Increasing the number of bolts contributes to significantly reduce the rock breakage region and bond breakage number. A threefold reduction of the number of broken bonds occurs passing from 4 to 12 rock bolts. The reinforcement of rock bolts is not obvious when the length is less than 0.5r0, however, the increase of bolt length is not efficient in preventing rock breakage when the length exceeds 1.0r0-1.2r0. Therefore, a reasonable efficient bolt length is suggested under the specific conditions of this study.