Stability analysis of surrounding rock under anchorage mechanics effect

In order to analyze the influence of anchor bearing layer formed under the coupling effect of anchor and sur- rounding rock on the stability of roadway surrounding rock,the surrounding rock was divided into plastic zone and elas- tic zone according to the stress distribution curve of surrounding rock. Combined with Mohr-Coulomb criterion,in ana- lyzing the change of volume force caused by bolt pre-tightening force,the analytical expression of the tangential stress within anchor bearing layer can be obtained. From the static equilibrium equation,it can derive the equivalent support- ing force provided by the anchor bearing layer boundary and the calculation analytical expression of the stress,radius and roadway displacement within the plastic zone of roadway surrounding rock under the action of equivalent supporting force. The mechanical effects of the pre-tightening force,length and row spacing of the full-length anchor bolt on roadway sur-rounding rock were analyzed by the above calculated analytical expressions. The results show that the equiv-alent support force has a certain influence on the stability of roadway surrounding rock. Under the effect of the equivalent support force,the stress analysis of roadway surrounding rock shows that the stress peak value of surround- ing rock changes and the position shifts to the roadway wall. The greater the pre-tightening force of the full-length an- chorage bolt,the longer the length of the bolt and the denser the row spacing,and the greater the equivalent support force within the range of the anchorage bearing layer,the better the stability of the roadway surrounding rock. The thickness of anchor bearing layer is proportional to the size of the equivalent support force. With the increase of the e- quivalent support force,the plastic zone range and surface dis-placement of roadway surrounding rocks will decrease significantly,and the equivalent support force has a good inhibitory effect on the stability of surrounding rocks. The theoretical analysis results were verified by FLAC3D numerical simulation. According to the plastic zone radius and roadway surface displacement anal-ysis under the action of the simulated anchorage bearing layer,the numerical simu- lation results were basically consistent with the theoretical analysis results.