Date of Award

5-2009

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Civil Engineering

Advisor

Andrus, Ronald D

Committee Member

Ravichandran , Nadarajah

Committee Member

Nielson , Bryant G

Committee Member

Juang , Hsein C

Abstract

Presented in this dissertation are the results of various studies conducted to characterize the liquefaction resistance of aged natural deposits. The data considered include laboratory and field test results from sites in five countries with particular focus on multiple locations in the South Carolina Coastal Plain.
A new liquefaction potential map of the peninsula of Charleston, South Carolina, is presented. Liquefaction potential is expressed in terms of the liquefaction potential index (LPI) developed by Iwasaki et al. and calculated using 44 cone penetration test (CPT) profiles. The CPT profiles are supplemented with information from the 1:24,000 scale geologic map by Weems and Lemon, several first-hand accounts of liquefaction and ground deformation that occurred during the 1886 Charleston earthquake, and liquefaction probabilities determined by Elton and Hadj-Hamou based on standard penetration tests. Nearly all of the cases of liquefaction and ground deformation occurred in the Holocene to late Pleistocene beach deposits that flank the higher-ground sediments of the Wando Formation. To match the observed field behavior, a deposit resistance correction factor of 1.8 is applied to the cyclic resistance ratios calculated for the 100,000-year-old Wando Formation.
The liquefaction susceptibility of four clayey soils in the Charleston is examined using primarily CPT measurements. The liquefaction susceptibility criteria by Robertson and Wride appear to be adequate for the three younger clayey soils, which are Holocene and Pleistocene estuarine deposits. On the other hand, as noted previously by Li et al., the Robertson and Wride criteria incorrectly predict susceptible for the Tertiary-age clayey soil, called the Cooper Marl. A new CPT-based liquefaction susceptibility chart that better predicts susceptibility of clayey soils is presented.
Data from over 30 sites in 5 countries are analyzed to develop updated factors for correcting liquefaction resistance of aged sand deposits. Results of cyclic laboratory tests on relatively undisturbed and reconstituted specimens suggest an increase in liquefaction resistance of 12% per log cycle of time and a reference age of about 2 days. Laboratory and field test results combined with cyclic resistance ratio (CRR) charts suggest an increase in liquefaction resistance of 13% per log cycle of time and a reference age of 23 years. A reference age of 23 years seems reasonable for the commonly used CRR charts derived from field case history data. Because age of natural deposits is often difficult to accurately determine, a relationship between measured to estimated shear-wave velocity ratio (MEVR) and liquefaction resistance correction factor is also derived directly from the compiled data.
Also presented are the results of seismic crosshole tests conducted at the Clemson Research and Education Center (CREC) site, underlain by a beach sand deposit with age of about 100,000 years old. The crosshole shear-wave velocity measurements agree well with values obtained by seismic downhole CPT tests. Measured to estimated shear-wave velocity ratios (MEVR) are used to further characterize the CREC site.
A procedure for back-calculating deposit resistance factor (KDR) based on field performance data is proposed. In the procedure, the percent of liquefied area is estimated from field performance data and/or from MEVR data. The KDR back-calculation procedure is applied to the CREC site and the Charleston peninsula. The back-calculated KDR values for the Wando Formation on the Charleston peninsula and at the CREC site are 1.7 and 1.9, respectively. The results provide strong support for the proposed procedure.

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