Optimization Analysis of Rockbolts Supporting for Double-Arch Shallow Tunnels Subjected to Unsymmetrical Loads

Abstract

Employing the explicit finite difference code based on strength reduction method, this paper optimizes the rockbolt length and circumferential distance of shallow double-arch tunnels subjected to unsymmetrical loads. For the geological properties of shallow and large cross section tunnels, seepage influences are considered in the stability analysis. The distribution laws of rockbolt on circumferential and longitudinal orientation respectively are presented with numerical simulation method. The results show that the longitudinal space distances of rockbolt has great influence on the horizontal displacement of hance of double-arched tunnel, and the horizontal displacement of hance increases with the increasing of longitudinal space distance. However, the circumferential space distance has effect on the ground settlement, and the ground settlement increases with the increasing of circumferential space distance. According to the stress distribution of middle wall, it is found that the safety of tunnel does not increase with the increasing of the number of rockbolt. The reasonable rockbolt supporting parameters are given for benefiting tunnel design.