Degree Type

Dissertation

Date of Award

2019

Degree Name

Doctor of Philosophy

Department

Civil, Construction, and Environmental Engineering

Major

Civil Engineering

First Advisor

Jeramy C. Ashlock

Abstract

Three dimensional dynamic soil-pile group interaction has been a subject of significant research interest over the past several decades, and remains an active and challenging topic in geotechnical engineering. A variety of dynamic excitation sources may potentially induce instabilities or even failures of pile groups. Employing modern experimental and numerical techniques, the dynamics of pile groups is examined in this study by integrated physical and computational simulations. In the physical phase, full-scale in-situ elastodynamic vibration tests were conducted on a single pile and a 2×2 pile group. Comprehensive site investigations were conducted for obtaining critical soil parameters for use in dynamic analyses. Broadband random excitation was applied to the pile cap and the response of the pile and soil were measured, with the results presented in multiple forms to reveal the dynamic characteristics of the pile-soil system. In the computational phase, the BEM code BEASSI was extended and modified to enable analysis of 3D dynamic pile group problems, and the new code was validated and verified by comparison to reference cases from the literature. A new theoretical formulation for analysis of multi-modal vibration of pile groups by accelerance functions is established using the method of sub-structuring. Various methods for interpreting the numerical results are presented and discussed. Case studies and further calibration of the BEM soil profiles are conducted to optimize the match between the theoretical and experimental accelerance functions. Parametric studies are performed to quantify the influence of the primary factors in the soil-pile system, including the soil modulus and damping profiles in the disturbed zone and the half-space, thickness of layers used in discretization of the soil profiles, and properties of the superstructure. It is shown that the new 3D disturbed zone continuum models can help improve the accuracy of dynamic soil-pile interaction analysis for pile groups in layered soils. This study therefore helps to advance the fundamental knowledge on dynamic soil-pile interaction by improving the accuracy of current computational models, and contributing additional physical tests to the experimental database in the literature. The specific impedance functions generated herein can be immediately used in practice, and the underlying general 3D disturbed-zone computational framework can readily be applied to other pile group problems of interest to researchers and practitioners.

Copyright Owner

Zhiyan Jiang

Language

en

File Format

application/pdf

File Size

405 pages

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