Numerical modeling of subway tunnels in liquefiable soil under earthquakes and verification by centrifuge tests

Underground structure in saturated sandy soil might be subject to severe damage due to seismic liquefaction.Numerical simulation for earthquake response of subway tunnels in liquefiable soil was conducted by use of finite element program DIANA SWANDYNE-II and the numerical model was verified by some centrifuge test results.A generalized plasticity model,Pastor-Zienkiewicz III,was used to model the dynamic behavior of saturated soil.Finite element procedure based on the u-p form of Biot equations was employed to perform the coupling analysis.It was shown that the numerical model could simulate the earthquake response of subway tunnels in liquefiable soil reasonably.Liquefaction induced ternal force in tunnel segments and its uplift were mainly influenced by the excess pore pressure and the earth pressure increment during earthquakes.Cut-off walls could reduce the uplift of subway tunnels effectively.