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Title:Dynamic soil modeling in site response and soil-large pile interaction analysis
Author(s):Phillips, Camilo
Director of Research:Hashash, Youssef M.; Olson, Scott M.
Doctoral Committee Chair(s):Hashash, Youssef M.
Doctoral Committee Member(s):Olson, Scott M.; Tutumluer, Erol; Ghaboussi, Jamshid
Department / Program:Civil & Enviromental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):soil dynamics
lateral spreading
lateral spreading against large rigid foundations
Abstract:The present research explores the use of numerical solutions in two geotechnical earthquake engineering problems; 1) one dimensional wave propagation in soil deposits and 2) the effects of lateral spreading on large pile foundations. Two new soil damping formulations are implemented in non-linear one-dimensional site response analysis for small and large strains. The first formulation introduces an approach to construct a frequency-independent viscous damping matrix which reduces the over-damping at high frequencies, and therefore, the filtering at those frequencies. The second formulation introduces a reduction factor that modifies the extended Masing loading/unloading strain-stress relationship to match measured modulus reduction and damping curves simultaneously over a wide range of shear strains. A set of examples are introduced to illustrate the effect of using the two proposed formulations, separately and simultaneously, in non-linear site response analyses. Three-dimensional numerical models are developed and calibrated using the displacement, acceleration, and pore water pressure time histories recorded in a free-field lateral spreading centrifuge test. The calibration process highlights the important role of small strain damping and the need for pressure-dependent dilation parameters to simultaneously provide the best match for measurements of pore water pressure, acceleration, and lateral displacement. The calibrated numerical model is then used to predict another free-field lateral spreading centrifuge test using the same soil profile but different input acceleration time history. The computed response shows good agreement with the centrifuge test measurements. Lateral pressures induced by lateral spreading soils against large piles are estimated using the results of three-dimensional numerical simulations. The numerical simulations were calibrated and evaluated using displacement, acceleration, and pore water pressure time histories recorded from lateral spreading centrifuge tests with a large, rigid deep foundation element located in the path of downslope soil movement. The calibration process highlighted the important role of soil-pile interface modeling to simultaneously provide the best match for measurements of pore water pressure, acceleration, and lateral displacement. The numerical model is then employed to determine the effects of using representative permeability values and broadband input motions. Pressures extracted from these numerical analyses are used to determine pressure profiles and bending moments and compared with current recommendations (i.e. strain wedge method and triangular net pressure distribution). The computed response agrees well with the results of the strain wedge method for the upslope side of the pile and shows the need for adjusting the triangular pressure method to estimate the lateral loads and bending moment in the pile at different depths by introducing a depth-dependent coefficient.
Issue Date:2013-02-03
Rights Information:Copyright 2012 Camilo Phillips
Date Available in IDEALS:2013-02-03
Date Deposited:2012-12

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