The liquefaction-induced lateral spreading of the fluvial terraces can cause tremendous physical damage to the natural and built environments in the lower reaches of Yangtze River. This paper presents an integrated nonlinear site response analyses method to characterize the large-scale lateral spreading behavior in the wide river valley of Yangtze River at the scale of several kilometers in the Abaqus/Explicit code, incorporating the main features such as the spatial variability of liquefiable deposit, the liquefaction initiation and cyclic mobility at the post liquefaction stage and the geometric nonlinearity induced by the extensively large deformation. In particular, the large-deformation behavior in the numerical model is simulated by the plasticity-based model at the element level and the arbitrary Lagrange-Euler (ALE) method at the model mesh level. The key factors influencing lateral spreading behavior are investigated, involving the ground motion characteristics, the slope angle of fluvial terraces, and the spatial variability of site condition. The numerical results indicate significant spatial variation characteristics of the lateral spreading of the fluvial terraces, triggered in the slightly inclined slope. Three generation stages of lateral spreading could be identified in the time-history curve of lateral displacement, i.e. swing stage, slip stage and creep stage, respectively. Finally, the model performance of the proposed modelling method is evaluated against the widely-used empirical formula, and the difference between each other is interpreted, which provides new insights into the mechanism of liquefaction-induced lateral spreading of the fluvial terraces in the wide river valley.

In order to study the deformation law and failure characteristics of shield tunnel obliquely crossing ground fissure under earthquake action, taking the shield tunnel of Xi 'an Metro Line 8 crossing f3 ground fissure as the engineering background, the 1: 20 shaking table model test method was used to analyze the strain of shield tunnel, the contact pressure with surrounding rock soil, the dislocation of segment and the axial force of bolt in detail, and the seismic damage mechanism and failure characteristics of shield tunnel obliquely crossing ground fissure were obtained. The test results show that under the action of earthquake, the shield tunnel has complex three-dimensional deformation characteristics, among which the vertical deformation is the most obvious. The deformation is mainly concentrated in the location of the ground fissure. The tensile strain and contact pressure of the hanging wall of the tunnel segment are greater than the strain value and contact pressure of the footwall. Because the vertical deformation of the tunnel is the largest, the bolts at the vault and the arch bottom are most obviously pulled. Excavation after the test, it can be seen that the tunnel appeared the phenomenon of ring joint opening, lining cracking and other damage. Under the action of the earthquake, the shield tunnel across the ground fissure is mainly subjected to tensile failure. The failure area is within 10 m from the ground fissure in the hanging wall and footwall, and the total length is 20 m. The closer to the ground fissure, the more serious the damage. The research results provide a scientific and reasonable reference for the subsequent construction and disaster prevention and mitigation design of Xi 'an Metro.

As a long lifeline system of buried structures, the utility tunnel (UT) is vulnerable to earthquake invasion. For utility tunnels with inverted siphon arrangements crossing rivers, the seismic response is more complex due to the basin effect of acceleration in the topography and the influence of fluctuating hydrodynamic pressure, but there is currently a gap in targeted seismic response analyses and references. Based on a UT project in Haikou, this paper studied seismic responses of a cast-in-place UT considering the coupled model of water-soil-tunnel structure on ABAQUS software. Herein, the dynamic fluctuation of hydrodynamic pressure is simulated using an acoustic-solid interaction model. A viscoelastic artificial boundary was used to simulate the soil boundary effect, and seismic loads were equivalent to nodal forces. Considering seismic invading direction and varying water elevation, this paper investigates the dynamic response characteristics and damage mechanisms of river-crossing utility tunnels. This study shows that the basin effect causes the soil acceleration around the UT to show variability in different sections, and the amplification factor of the peak acceleration at the central location is almost doubled. The damage and dynamic water pressure of the UT are intensified under bidirectional seismic excitation, and the damage location is concentrated at the junction of the horizontal and the vertical section. Bending moments and axial forces are the main mechanical behaviors along the axial direction. Changes in river levels have a certain positive effect on the UT peak MISES, DAMAGEC, and SDEG, and it exhibits a certain degree of energy dissipation and seismic damping effect. For the aseismic design of cross-river cast-in-place utility tunnels, bidirectional seismic calculations should be performed, and the influence of river hydrodynamic pressure should not be neglected.