Collapse mechanism of cut-and-cover tunnels under seismic loading

Abstract

We investigate the collapse mechanism of rectangular cut-and-cover tunnels under seismic loading from inelastic frame analyses. The propagation of plastic hinges in the reinforced concrete lining is observed. It is shown that the plastic hinge start to form at the bottom corners of the structure. The shear strain at which the plastic hinge start to develop and tunnel collapses are investigated. Whereas the plastic hinge develops at a shear strain of 1.2 % for soils with a shear velocity of 50 m/s, it is formed at a low shear strain of 0.04 % for a soil with a shear velocity of 400 m/s. The shear strain-moment diagram proposed in this study provide a simple yet robust method to evaluate the seismic performance of cut-and-cover box tunnels under seismic loading.