VERTICAL VIBRATIO' OF PILE I' SATURATED SOIL CO'SIDERI'G SOFTE' REGIO'S OF SURROU'DI'G SOIL

摘要

There has been a considerable interest in dynamic interaction of pile-soil system due to its important applications in machinery foundations, seismic design of structures and pile dynamic testing. Vertical vibration of a pile embedded in saturated soil layer is investigated incorporating the nonlinear behavior of soil in the vicinity of the pile. The pile is dealt with one-dimensional elastic theory. The soil surrounding the pile is divided into two regions: an outer infinite linear saturated poroelastic medium and an inner soften zone in the shape of a hollow cylinder. A set of simplifications is incorporated to soften inner zone and it can be analyzed by cavity expansion theories. Using variable separation method, governing differential equations of the undisturbed region of saturated soil are decoupled by introducing the potential functions. Based on the boundary and continuity conditions of the inner and outer region, pile dynamic responses are presented to an arbitrary vertical load. Numerical results from frequency domain and time domain indicated that the soften region of soil has significant influence on the dynamic response of pile-soil system under vertical vibrating of pile in saturated soil. By comparison of the present solutions with the ones not considering soften region, the results show that there are obvious differences of dynamic responses at pile head. A conclusion can be deduced that the interaction of pile and soil is overestimated under the ideal undisturbed model. And the presented model makes it possible to predict accurately the dynamic responses of pile and soil system.