Semester of Graduation

Fall 2018

Degree

Master of Science in Civil Engineering (MSCE)

Department

Department of Civil & Environmental Engineering

Document Type

Thesis

Abstract

The in-situ cone and piezocone penetration tests (CPT, PCPT) has been widely used by the geotechnical engineering community for subsurface soil characterization and classification, and for the evaluation of many engineering soil properties, such as undrained shear strength (su), unit weight (γ), constrained modulus (M), coefficient of consolidation (cv), and stress history (OCR). The objective of this research study was to estimate the undrained shear strength of clayey soil using CPT/PCPT data in addition to some soil boring log data. At the same time, soil classification charts/methods based on CPT/PCPT were investigated and modified. For this purpose, 70 cone penetration test data collected from 14 different parishes in Louisiana were analyzed. In each site, both laboratory and CPT tests were performed at the same location in order to evaluate the soil parameters (e.g., corrected cone tip resistance, qt; sleeve friction, fs; total overburden pressure, σvo; plasticity index, Ip; Liquid limit, LL; and moisture content, MC). Both linear and non-linear statistical regression models were developed and verified using the measured soil parameters to estimate su of clayey soil for individual soil layers. The su model that contains qt, fs, and σv0 parameters is found to be the best model that satisfies all the statistical parameters, and that the estimated values of su are close to the measured values. In addition, three basic soil zones (e.g., sandy, silty and clayey) have been modified in some CPT/PCPT based soil classification charts. The CPT/PCPT soil classification charts investigated in this study include Douglas and Olsen (1981) chart, modified Schmertmann chart by Tumay (1985), Robertson (1990, 2009 and 2010) charts, Saye et al. (2017) chart, and Zhang and Tumay (1999) probability method. Among these charts, the Robertson (2010) chart showed better prediction to categorize soils for Louisiana. In addition, the Zhang and Tumay (1999) probability method is found to be suitable to categorize the sandy and clayey soil type behavior, but was not so clear for the silty soil behavior.

Date

8-30-2018

Committee Chair

Abu-Farsakh, Murad Yusuf

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