Vertical Vibration Characteristics of a Variable Impedance Pile Embedded in Layered Soil

Wenbing Wu,Changliang Fang,Xuelian Xu,Hao Liu,Bin Dou,Rongzhu Liang

doi:10.1155/2017/1794950

Abstract

In engineering applications, various defects such as bulging, necking, slurry crappy, and weak concrete are always observed during pile integrity testing. To provide more reasonable basis for assessing the above defects, this paper proposed simple and computationally efficient solutions to investigate the vertical vibration characteristics of a variable impedance pile embedded in layered soil. The governing equations of pile-soil system undergoing a vertical dynamic loading are built based on the plane strain model and fictitious soil pile model. By employing the Laplace transform method and impedance function transfer method, the analytical solution of the velocity response at the pile head is derived in the frequency domain. Then, the corresponding semianalytical solution in the time domain for the velocity response of a pile subjected to a semisinusoidal force applied at the pile head is obtained by adopting inverse Fourier transform and convolution theorem. Based on the presented solutions, a parametric study is conducted to study the vertical vibration characteristics of variable cross-section pile and variable modulus pile. The study gives an important insight into the evaluation of the construction quality of pile.

Highlights

With the wide application of piles for supporting various upper structures all over the world, the construction quality of pile foundations has attracted increasing attention in recent decades
Van Koten et al [5] primarily utilized a distributed system of single Voigt unit to simulate the soil reactions acting on the pile and derived an analytical solution for the dynamic interaction of pile-soil system
Based on the above literature review, the main objective of this study is to develop simple and computationally efficient solutions for the analysis of vertical vibration characteristics of a variable impedance pile embedded in layered soil

Summary

Introduction

With the wide application of piles for supporting various upper structures all over the world, the construction quality of pile foundations has attracted increasing attention in recent decades. Since the pile dynamics is the basis of various methods of dynamic pile testing, many investigators have paid their attention to develop various dynamic interaction models for the dynamic response of pile subjected to vertical loads. It is worth noting that the plane strain model is one of the most important methods to simulate the interaction between pile and surrounding soil due to its compact and elegant properties; that is, there is zero strain in the vertical direction and the stress waves propagate only in the horizontal direction. Nogami and Novak [18] first adopted a threedimensional continuum model (i.e., the soil layer is threedimensional and its wave effect is considered) to investigate the vertical vibration of pile foundation. A parametric study is conducted to investigate the influence of pile properties on the vertical dynamic response of the variable impedance pile

Mathematical Model and Assumptions

Governing Equations and Their Solutions

Parametric Study and Discussion

Conclusions