Seismic Response of Utility Tunnels with Different Burial Depths at the Non-Homogeneous Liquefiable Site

Damage to underground structures induced by soil liquefaction under cyclic loads such as earthquakes has long been an important issue in underground engineering practice. In this paper, five models are developed using Flac3D software to analyze the effect of burial depth on the force, deformation characteristics, and uplift behavior of utility tunnels in the non-homogeneous site containing a liquefied layer. The cyclic shear property of saturated sand and the increase in pore water pressure during the earthquake are modeled using a cyclic load-volume strain increment model, using Shell-Type structural elements to model underground utility tunnels, and by using plastic hinges to represent the bending moment capacity of member's joints. Numerical results show that for shallow-buried utility tunnels, increasing the burial depth increases the bending moment, shear force, and deformation of the structure while significantly reducing its uplift. Therefore, for high-strength shallow-buried utility tunnels, appropriate increase in burial depth can improve its seismic safety.