Abstract:

The dynamic responses of a pile foundation under hammer impact are analyzed. The concrete pile in soil is modeled as a (standard linear solid) viscoelastic rod buried in a (Voigt-type) viscoelastic media. The upper end of the pile is subjected to a mass impact; and lower end is supported by a spring-dashpot foundation. Governing equations for the pile movement are given. Coupled boundary conditions at the upper and lower ends are deduced respectively using the dynamic equation for the hammer and the constraint equation for the foundation. The initial-boundary value problem is solved by using Laplace transform with respect to time variable to the equations. An exact solution for the stress distribution in the pile is obtained in the transformed domain. Using numerical inversion technique the stress-time curves at any sites of the pile can be calculated. Examples are given to show that the approach can be conveniently applied to analyzing the generation, propagation, reflection and interactions of the viscoelastic stress waves in the pile.

Key words: pile foundation properties, viscoelastic stress wave, Laplace transform, numerical inversion