Undrained shear strength based on piezocone and laboratory tests for tropical soils

Abstract

This paper presents a study on the geotechnical properties of two residual soil sites (Buloba a less seismic zone and Buliisa an extreme seismic zone in Uganda) to characterize, propose and recommend models for the estimation of Undrained shear strength (Su). The analysis utilized data from 32 (Thirty-Two) piezocone penetration tests, Twenty-Eight (28) Liquid Limit tests, Twenty-Eight (28) Plastic Limit tests, Twenty-Eight (28) Linear Shrinkage tests, Twelve (12) Consolidation tests, 13 (Thirteen) Consolidated Undrained Triaxial tests. The results showed that the fine content, natural moisture content, liquid limit, plasticity index, and linear shrinkage varied within each site. Furthermore, the undrained shear strength, internal friction, and cohesive values also varied between sites. The study proposed appropriate empirical correlations for obtaining the Su of residual soils, and observed that Nkt value of 56 is proposed for slightly consolidated residual soils while Nkt = 288 should be used for heavily consolidated residual soils during the obtaining of the Su. Furthermore, the study concluded that SHANSEP constants of s = 0.07 and m = 0.82 should be appropriate for estimating the undrained shear strength of residual soils. However, caution should be taken as these empirical relationships are site-specific and considerate of uncertainties. Overall, this paper provides valuable insights for geotechnical engineers to consider for residual soil analysis.