Date of Award

Fall 2020

Project Type

Dissertation

Program or Major

Civil Engineering

Degree Name

Doctor of Philosophy

First Advisor

Majid Ghayoomi

Second Advisor

Stephen Jones

Third Advisor

Jean Benoit

Abstract

The vast majority of surface structures are located on or surrounded by unsaturated and partially saturated soil deposits. Previous studies revealed that degree of saturation in soils can significantly impact the seismic performance of geotechnical systems. Yet, the fundamental understanding of the mechanisms by which the degree of saturation impacts their performance during seismic loading is not mature. This Ph.D. dissertation aimed to evaluate and characterize the dynamic response of soils including excess pore pressure generation, induced volumetric deformation, shear modulus, and material damping at different states of saturation and a wide range of degrees of saturation. Three different desaturation methods, including Microbial Induced Partial Saturation (MIPS), wet-compaction, and tensiometric suction control techniques were used to evaluate the impact of state of saturation, saturation level, and the path to reach that level on the dynamic properties and performance of sands containing variable non-plastic fines. Results from this study indicated that MIPS treatment of soil specimens, even with a small reduction in degree of saturation, can result in a significant reduction in the excess pore pressure generation. Experimental data suggested a meaningful impact of the state of saturation and desaturation technique on dynamic response of tested specimens. On the basis of experimental data and theoretical considerations, semi-empirical models were developed to estimate the excess pore pressure generation and volumetric deformation in sand and silty sands under unsaturated and partially saturated states. The comparison of experimental measurements as well as available data in literature showed the suitability of the developed models to capture the trends in dynamic soil response with the degree of saturation.

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