Seismic tunnel response in jointed rock mass

Abstract

A series of pseudo-static discrete element analyses are performed to evaluate the effect of rock joint on the seismic response of tunnels. The parameters considered joint spacing, stiffness and strength, and dip. The results show that the joint stiffness and strength have the most critical influence on the tunnel response. Increase in the spacing of the joints results in localized concentration of shear deformation, and hence the moment and shear stress of the tunnel lining increase accordingly. The tunnel response is shown to be lowest for joints dipping at 45°, while the responses are largest for vertical and horizontal joints. In summary, it is shown that smooth, widely spaced joints with shear stiffness lower than 0.25 GPa/m can significantly increase the tunnel response under seismic loading. The tunnel linings are shown to be most susceptible to damage due to induced shear stress, and therefore should be checked in the seismic design.