Xianzhang Ling

Numerical simulations of shake-table experiment for dynamic soil-pile-structure interaction in liquefiable soils

A shake-table experiment on pile foundations in liquefiable soils composed of liquefiable sand and overlying soft clay is studied. A three-dimensional (3D) effective stress finite element (FE) analysis is employed to simulate the experiment. A recently developed multi-surface elasto-plastic constitutive model and a fully coupled dynamic inelastic FE formulation (u-p) are used to model the liquefaction behavior of the sand. The soil domains are discretized using a solid-fl uid fully coupled (u-p) 20-8 noded brick element. The pile is simulated using beam-column elements. Upon careful calibration, very good agreement is obtained between the computed and the measured dynamic behavior of the ground and the pile. A parametric analysis is also conducted on the model to investigate the effect of pile-pinning, pile diameter, pile stiffness, ground inclination angle, superstructure mass and pile head restraints on the ground improvement. It is found that the pile foundation has a noticeable pinning effect that reduces the lateral soil displacement. It is observed that a larger pile diameter and fixed pile head restraints contribute to decreasing the lateral pile deformation; however, a higher ground inclination angle tends to increase the lateral pile head displacements and pile stiffness, and superstructure mass seems to effectively influence the lateral pile displacements.

Experimental and numerical investigation on the dynamic response of pile group in liquefying ground

The response of pile foundation in liquefiable sand reinforced by densification techniques remains a very complex problem during strong earthquakes. A shake-table experiment was carried out to investigate the behavior of a reinforced concrete low-cap pile group embedded in this type of ground. In this study, a three-dimensional (3D) finite element (FE) analysis of the experiment was conducted. The computed response of the soil-pile system was in reasonable agreement with the experimental results, highlighting some key characteristics. Then, a parametric study was performed to explore the influence of pile spacing, pile stiffness (EI), superstructure mass, sand permeability, and shaking characteristics of input motion on the behavior of the pile. The investigation demonstrated a stiffening behavior appearing in the liquefied mediumdense sand, and the pile group effect seemed negligible. Furthermore, the kinematic effect was closely connected with both EI and sand permeability. Nevertheless, the inertial effect was strongly influenced by the superstructure mass. Meanwhile, high frequency and large amplitude of the input motion could produced greater the pile’s moments. It is estimated that this case study could further enhance the current understanding of the behavior of low-cap pile foundations in liquefied dense sand.

Seismic Performance of a Soil-Pile-Bridge: Three-Dimensional Finite Element Simulation

Soil-Structure Interaction (SSI) is involved in the seismic performance of pile-supported bridge. Such effect includes soil-pile interaction driven by the deformation of pile and surrounding soil. This interaction might be further pronounced due to large soil deformation during earthquake. To capture this characteristic, a three-dimensional (3D) finite element (FE) simulation is conducted considering soil-pile interaction along with the corresponding numerical details. The prototype system of a two-span reinforced concrete bridge with a single pier is demonstrated in multi-layered clay. The overall seismic response of the coupled soil-pile-bridge system are systematically investigated. The simulated results showed that the inertial effect of superstructure and transversal configuration of bridge significantly influence the pile response. The analysis technique as well as the derived insights are of significance to general pile-supported bridge system configurations.

Performance Assessment of a Concrete Gravity Dam at Shenwo Reservoir of China Using Deterministic and Probabilistic Methods

NSFC [51261120376, 11102174, 51281220267]; Open Research Fund Program of State key Laboratory of Hydroscience and Engineering [sklhse-2013-C-02]; Administration department of Shenwo Reservoir