Earthquake Simulation Response Of Soil-pile System In Liquefaction-induced Lateral Spreading Ground

Liquefaction-induced lateral spreading is one of main reasons for the damage to pile foundation during earthquake. Shake-table experiment is one of the most effective approaches for studying soil-pile interaction in liquefaction-induced lateral spreading ground. Numerical simulation is not only an effective supplement of shake-table experiment, but also it is the necessary technique step from converting theoretical work to engineering project. However, the current research work mainly focus on the numerical simulation of laboratory test and quasi-static computation. There are still lack of sufficiently experimental and theoretical basis for applying it to the engineering project. On the above, the aim of present work is to study the soil-pile interaction system in liquefaction-induced lateral spreading ground during earthquake. The simplified analysis procedure of soil-pile interaction is developed and the connection of soil-pile interaction is proposed based on large-scale shake-table experiment and theoretical analysis. Meanwhile, this connection will be applied to numerical model of shake-table experiment on pile foundation in liquefaction-induced lateral spreading ground. The main influence factors are studied related to numerical model. In addition, nonlinear pile foundation and great lateral spreading deformation will result in massive computation. To improve the computational efficiency, the parallel numerical model of shake-table experiment on pile group is established and the validation of model is performed. Finally, the above mentioned method will be applied to the numerical modeling of prestressing concrete pile group in actual liquefaction-induced lateral spreading ground. Main content, method, and results are as follow:1. Large-scale shake-table experiment on pile foundation(single pile and pile group) in liquefaction-induced lateral spreading ground. Shake-table experiment aims to the characteristic of the waterfront liquefaction-induced lateral spreading ground and refers to the design experience of similar shake-table experiment. Shake-table experiment on pile foundation is conducted in liquefaction-induced lateral spreading ground through installing quay wall induced the lateral spreading of liquefied sand. Excess pore pressure, acceleration, and lateral spreading displacement of soil layer are analyzed as well as lateral displacement and bending moment of pile.2. Simplified analysis method of single pile in liquefaction-induced lateral spreading ground. Based on the shake-table experiment on single pile and Beam on Nonlinear Winkler Foundation model(BNWF model), this model employs an elastic beam element to simulate the pile and a modified nonlinear p-y spring element to represent the liquefied soil. The pile base connection finite stiffness is defined using a zero-length element. The lateral spreading deformation is simulated by imposing an experimental recorded displacement profile at the end of any nonlinear p-y spring element. Based on above, the simplified analysis method of soil-pile interaction is established in liquefaction-induced lateral spreading ground. The validation of this method is verified by comparing the experimental results. Meanwhile, the effect of pile modulus, diameter and stiffness on pile response are analyzed.3. Connection of soil-pile interface. The proposed connection of soil-pile interface includes two types of zero length element on the basic of the rigid link of soil-pile interface. This connection can simulate the coupled effect of shear force on the soil-pile interface and mimic the slip of soil-pile interface during earthquake. This will avoid the overlarge axial force on pile foundation during lateral spreading.4. Numerical simulation of shake-table experiment on single pile in liquefaction-induced lateral spreading ground. According to the shake-table experiment, the numerical model employs the initial state analysis. The surface water is modeled by imposing nodal water pressure and force, and the quay wall is simulated by paralleling linear beam element. Numerical model of shake-table experiment on single pile is established using the proposed soil-pile connection. The model is verified in comparison with experimental results. On the basic, the influence of damping, permeability, and superstructure mass on soil-pile dynamic interaction are analyzed.5. Numerical simulation of shake-table experiment on pile group in liquefaction-induced lateral spreading ground. Based on the numerical model of shake-table experiment on single pile, the numerical model of shake-table experiment on pile group is developed and verified by converting from the single pile to pile group. Based on above, the parallel numerical model of shake-table experiment on pile group is developed considering nonlinear property of concrete pile. The parallel computation method is validated by the sequential computed results. The moment-curvature and fiber strain response of pile group are mainly analyzed.6. Numerical simulation of prestressing concrete pile group in actual liquefaction-induced lateral spreading ground. The prestressing concrete pile and soil layer are established separately in numerical model considering the prestressing concrete pile characteristic, which make sure that the concrete pile deformed freely under prestressing. Meanwhile, the soil displacements are re-set to zero using initial state analysis. On this basis, soil and pile meshes are assembled by the above proposed soil-pile connection. The large-scale parallel numerical model of prestressing concrete pile group is developed in actual liquefaction-induced lateral spreading ground. The axial and shear force, bending moment, curvature and fiber strain response are analyzed during earthquake.The presented results further highly improve the understanding of seismic response and damage of pile foundation in liquefaction-induced lateral spreading ground, especially the finished large-scale shake-table experiment on pile foundation, related numerical simulation, parallel numerical simul ation on pile group, and recognition obtained from related analysis. This will provide the necessary technical details for similar experiment and numerical simulation. This also will have an important significance for studying the seismic response of pile foundation and simultaneously provide valuable basic data for gradually improving the seismic design of pile foundation in liquefaction-induced lateral spreading ground.