Theoretical Study And Application On Dynamic Testing Of Three-Dimensional Viscoelastic Pile

As an important form of basic, Pile foundation is widely used in engineering practice. Low strain testing technology plays an important role for pile foundation integrity testing. Under viscoelastic conditions three-dimensional dynamic responses of Large-diameter piles for transient vibration is mainly studied, the stress wave propagation characteristic in pile-soil is discussed. It shows a good guidance for engineering practice.The pile-soil are considered as viscous-elastic in this paper, a three-dimensional pile-soil system transient vibration calculation model is established by three-dimensional viscoelastic wave equation, and the definition solution is obtained. MATLAB program is compiled by discrete differential of staggered grid finite difference method and introducing the Higdon artificial absorbing boundary. We achieved the numerical calculation of pile dynamic response for transient vibration. By comparing with measured curves, one-dimensional semi-analytical solution theoretical results, the correctness of three-dimensional viscoelastic pile-soil model is proved. Vibration velocity is sampled under free surface pile and vertical axial plane midpoint of the pile, the stress wave propagation characteristic is intuitively displayed. Characteristic of pile vibration velocity response on different viscoelastic parameters is studied by numerical calculation. The best pick-up range in the low strain testing is proposed at large diameter pile. The influence of three-dimensional effect for large diameter pile is discussed. Different defect situation of pile such as necking, expanding, segregation is studied, characteristic of pile vibration velocity response on different defect situation is obtained. Characteristic of pile vibration velocity response on non-axisymmetric defect is studied, the wave snapshots at different time are obtained, which give a visual interpretation of propagation of wave in the pile defects.