School of Civil and Environmental Engineering

Ph.D. Thesis Defense Announcement

Multi-Scale Studies of Particulate-Continuum Interface Systems Under Axial and
Torsional Loading Conditions

By

Alejandro Martinez

Advisor:

Dr. J. David Frost

Committee Members:

Dr. Susan Burns (CEE), Dr. Paul W. Mayne (CEE), Dr. Arun M. Gokhale (MSE) and Dr. Gregory Hebeler (Golder Associates, Inc.)

Date & Time: Monday, November 9, 2015 at 11:00am

Location: Sustainable Education Building, 122

ABSTRACT:

The historical belief that particulate (soil) - continuum (manmade material) interfaces represent the weak link in most geotechnical systems has been shown to be incorrect for many situations. Namely, prescribing properties of the continuum material, such as its surface roughness and hardness, can result in interface strengths that are equal to the contacting soil mass internal shear strength. The research presented in this thesis expands the engineering implications of these findings by studying the response of interface systems in axial and torsional shear loading conditions. These studies show that taking a fundamental engineering approach to design the loading conditions induced to the interface system can result in interface strengths that exceed the previously considered limiting shear strength of the contacting soil. Fundamental experimental and numerical studies on specimens of different types of sand subjected to torsional and axial interface shear have shown that these are inherently different processes. Specifically, micro-scale soil deformation measurements have shown that torsional shear induces larger soil deformations as compared to axial shear, as well as complex volume change tendencies that consist of dilation and contraction in the primary and secondary shear zones. Studies on the global response of torsional and axial shear tests showed that they are affected differently by soil properties such as particle angularity and particle roughness. Discrete Element Modeling (DEM) simulations provided detailed information regarding the specimens' fabric evolution and shear-induced loading conditions. These findings allowed for the development of links between the measured micro-scale behavior and the observed global-scale response. The understanding of the behavior of torsional and axial interfaces provides a framework for the development of enhanced geotechnical systems. Applications to soil liquefaction assessment and deep foundations are provided, which have direct implications in engineering design since their implementation can result in more resilient and sustainable geotechnical systems.