Numerical simulation of an excavation disturbed zonearound a tunnel in brittle rock<速報>

The micromechanics-based damage model proposed by Golshani et al. (2005) is extended so that time-dependent behavior of brittle material can be taken into account, with special attention to the numerical analysis of an excavation damage zone (EDZ) around a tunnel, which is a major concern in assessing the safety of underground repositories. The present model is capable of reproducing the three characteristic stages of creep behavior (i.e., primary, secondary and tertiary creep) commonly observed in laboratory creep tests. Using the present model, sub-critical microcrack growth parameters (i.e. n and A) can be determined for Inada granite by fitting the numerical results of elapse time to failure versus the creep stress ratio curve with the experimental data under both dry and wet conditions. It is found that moisture has a significant influence on the parameter A rather than the parameter n. Use of the extended model makes it possible to analyze not only the extension of microcrack length, but also the development of the excavation damage zone (EDZ) around tunnels as a function of time. The disturbed zones mainly develop in the sidewalls of the tunnel in the case that the vertical stress is larger than the horizontal stress