Continuum representation of brittle rock failure bulking-induced displacements around tunnels

摘要

Mining tunnels continue to be excavated at increasingly greater depths, where it is a challenge to design, support and maintain stable openings. For ground support design, it is important to reasonably predict the extent of failure and the deformation behaviour of the rock mass. Currently, limited practical tunnel-analysis techniques are available for tensile-failure- dominated brittle rock-mass behaviour. This paper describes a numerical continuum-based method of brittle failure analysis that predicts both the extent of failure and provides an adequate continuum representation of brittle bulking deformations. The Damage Initiation Spalling Limit (DISL) approach, modified to account for stiffness degradation due to damage of the failed rock, is implemented into the two-dimensional continuum code FLAC. The technique is compared to empirical methods through an illustrative example and back-analysis of a case study with measured tunnel displacements.