Undrained Shear Strength of Very Soft to Medium Stiff Bangkok Clay from Various Laboratory Tests

Abstract

The values of undrained shear strength of undisturbed Bangkok Clay specimens are investigated by various laboratory tests, i.e. (i) unconfined compression test, (ii) unconsolidated undrained triaxial test, (iii) isotropically consolidated undrained triaxial compression/extension tests, (iv) K_o-consolidated undrained triaxial compression/extension tests, (v) direct shear test, (vi) direct simple shear test, (vii) laboratory vane test, and (viii) triaxial vane test. The experimental data are obtained from laboratory tests performed in this study and collected from previous published studies. The soil layers of interest in this study are very soft to medium stiff clays which are located between 2-14 m depth below ground surface. The variations of undrained shear strength with depth and their degree of scattering are presented and discussed. The interrelationships among undrained shear strengths from various laboratory tests are analyzed and relevant discussions are made. The validity of various empirical and theoretical relationships for predicting undrained shear strength of Bangkok Clay are evaluated. Various approaches for estimation of mobilized undrained shear strength for embankment stability analysis are investigated and the most suitable approach for embankment stability analysis and design on Bangkok subsoils is finally suggested.