Date of Award

Spring 1-1-2019

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Shideh Dashti

Second Advisor

Dobroslav Znidarčić

Third Advisor

John S. McCartney

Abstract

This study involved an investigation into the properties of Nevada sand under monotonic, cyclic sinusoidal, and irregular cyclic loading. The study also was used to determine the capabilities of the new Wille Geotechnik triaxial press that was purchased for use at the University of Colorado Boulder. The properties of Nevada sand are important to understand for the ongoing seismic research being conducted at CU Boulder, specifically for the calibration of numerical models to simulate the results of centrifuge testing. There had been previous work completed by others to define the monotonic and cyclic sinusoidal response of the soil, but the effects of irregular loading on Nevada sand has not been studied.

To study the properties of Nevada sand, isotropically consolidated undrained triaxial testing was conducted at various initial conditions and loading conditions. The steady state response of Nevada sand was studied and the phase transformation line was defined for axial compression loading. The cyclic properties of the soil were studied and the generation of excess pore water pressure was found to be independent of frequency of loading for sinusoidal loading when soil liquefaction was not observed. For irregular cyclic loading, the rate of increase in excess pore water pressure was greater than the cyclic sinusoidal tests, leading to accelerated axial strains. Finally, the shear modulus degradation was studied for all cyclic tests, and it was found that the scatter of the test data was larger than what the currently available procedures suggest.

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