Date of Award

2013

Degree Type

Thesis

Degree Name

Master of Science in Ocean Engineering

Department

Ocean Engineering

First Advisor

Chris Baxter

Abstract

The current state-of-the-practice for estimating the liquefaction potential of a site is to use correlations with the in situ tests such as the Standard Penetration Test (SPT), Cone Penetration Test (CPT), and shear wave velocity (Vs). In each method, field data has been collected from sites where either liquefaction or no liquefaction was observed following earthquakes.

These methods assume that the in situ measurement (SPT, CPT, or Vs) captures the liquefaction resistance of all coarse-grained soils. This has been shown to be true for the SPT and CPT, where resistance is related to the relative density of the soil. In contrast, shear wave velocity is a function of a soils’ void ratio, and soils with the same void ratio can have very different soil behavior. There is some evidence in the literature that the relationship between cyclic resistance and shear wave velocity may be soil specific, meaning that using a field-based Vs approach for liquefaction resistance for all sands may not be appropriate.

The objective of this study is to evaluate whether the Cyclic Resistance (CRR) - Shear Wave Velocity (Vs) relationship is soil specific for two soils. A laboratory program was developed and twenty-nine undrained cyclic triaxial tests were conducted with shear wave velocity measurements taken using bender elements.

Eleven cyclic triaxial tests were conducted on Monterey sand and eighteen cyclic triaxial tests were conducted on a calcareous sand from Cabo Rojo, Puerto Rico. Three different void ratios were chosen for each sand and the data was compared against published data on comparable soils.

The results suggest that the liquefaction resistance of both the Monterey and Cabo Rojo calcareous sand is lower than predicted by the field-based approaches of Andrus and Stokoe (2000) and Kayen et al. (2013). In this case, using the field-based shear wave velocity approach would significantly overestimate the liquefaction resistance of the Cabo Rojo and Monterey sands. More research is needed, however, the results of this study support the hypothesis that the Cyclic Resistance - Shear Wave Velocity relationship is soil specific.

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