Strength and Failure Behaviors of a Jointed Rock Mass Anchored by Steel Bolts: A Numerical Modeling Study

Large deformation of anchored rock masses or pull-out failure of anchor bolts often occurs in tunneling practices. The existence of incipient joints in rock masses might account for the failure of anchor bolts. The strength of the anchored rock mass varied with the geometric property of the joints and might be less than the target value. A series of numerical modeling experiments have been carried out in the present study by utilizing the FLAC(3D) software package. A novel method has been proposed to establish and validate numerical models such that they can simulate and extend physical experimental results. Accordingly, we demonstrated that the application of anchor bolts increases the strength of the jointed rock blocks but significantly depends on the orientation of incipient joints. The anchor bolt reduces the nonuniformity of the stress distribution, and the uniformity increases gradually with increasing bolt density. Moreover, the application of anchor bolts would keep the rock blocks as intact to contain the tendentious failure along the incipient joint planes. The findings in the present study would benefit the stabilization of rock masses adjacent to an underground tunnel, especially at the initial stage of failure when only incipient joints exist.

Automated summary

Large deformation of anchored rock masses or pull-out failure of anchor bolts often occurs in tunneling practices. The existence of incipient joints in rock masses might account for the failure of anchor bolts. The present study utilized numerical modeling experiments to investigate the effects of anchor bolts on rock mass stability. The findings demonstrate that anchor bolts increase the strength of jointed rock blocks and reduce the nonuniformity of stress distribution, thereby preventing tendentious failure along incipient joint planes.