Evaluating Deformation Modulus of Cohesive Soils from Piezocone Penetration Test for Consolidation Settlement

Abstract

The piezocone penetration test (PCPT) interpretation methods were evaluated for reasonable prediction of the deformation constrained modulus (M), which is needed to calculate the consolidation settlement of cohesive soil. Seven sites in Louisiana were selected for this study. In each site, PCPT tests were performed, and soundings of cone tip resistance (qc), sleeve friction (fs), and pore pressures (u1 and u2) were recorded. Dissipation tests were conducted at prespecified penetration depths and used to estimate the vertical coefficient of consolidation (cv) using the Teh and Houlsby interpretation method. High-quality Shelby tube samples were collected close to the PCPT tests and used to carry out a laboratory testing program, including consolidated undrained triaxial tests and one-dimensional consolidation tests. The constrained modulus (M) values predicted by using the different interpretation methods were compared with the reference values determined from the laboratory consolidation tests. Results of this study showed that the Sanglerat method was able to predict Mbetter than the other methods. Two correlations were also developed to predict M from the corrected cone tip resistance (qt) and the net cone tip resistance (qt - σvo). The results of this study were verified by comparing the predicted total and time rate of settlements estimated from piezocone penetration and dissipation data with the laboratory-calculated and field-measured settlements for three selected sites.