Integrated techniques for behavior evaluation of large-scale underground openings by using distinct element method

Abstract

The stability and support effects of large-scale underground openings located in the jointed rock masses are principally ruled by the mechanical behavior of discontinuities. The major deformations of the host rock masses containing underground openings originate from the normal and shear movements along the walls of discontinuities. A number of experimental and numerical investigations have demonstrated the significant influences of discontinuities on the mechanical, thermal and hydraulic behaviors of discontinuous rock masses, indicating that the deformational mechanism and stability of underground facilities in the discontinuous rock masses depend not only on the existing discontinuities but also the new cracks, which are generated and thereafter keep propagation due mainly to the stress relaxation induced by excavation. In this study, a two dimensional distinct element method was used to analyze the behavior of underground cavern based on in-situ geological data and experimental feature of rock joints. The properties of rock joints used in the analyses were obtained by using the newly developed high-performance direct shear test apparatus. Some local deformational behaviors of deep underground cavern influenced by the characteristics of discontinuity distributions were also discussed. A multiple system for analyzing the feature of geometrical distribution of rock joints was furthermore developed. The results revealed that the orientation, position and density of discontinuities around a cavern influence its deformational behavior and stability significantly.