Numerical modeling of a tunnel in jointed rocks subjected to seismic loading

Abstract

The studies on the performance of tunnels under static loads are reported extensively in the literature but their performances under dynamic loads are limited. The present study highlights some of the important aspects of jointed rock tunnels during seismic loading. The literature review provides a shake table experimental study of a jointed rock tunnel. A Universal Distinct Element Code (UDEC) model is developed from this shake table experiment. The model tunnel is subjected to a scaled input motion of the 1985 Mexico earthquake. The numerical results are validated systematically with the findings of the shake table experiment. Further, the developed numerical model is used to perform parametric studies to understand the effect of in-situ stress, joint angles, joint stiffness, and joint friction angle on the deformation and stability of the tunnel under the same earthquake input motion. It is observed that some joint angle combinations form a wedge that yields excessive deformation and subsequently a complete failure. An exponential decrease in deformation occurred in the tunnel as the joint stiffness increases. It is found that the shallow tunnels are more susceptible to damage under the action of earthquake loads.