Strength Anisotropy of a Residual Soil in Singapore

Abstract

The undrained shear strength of soil is one of the most important parameters required for geotechnical design. Depending on the design situations, the undrained shear strength of soil may have to be determined by different tests. In this paper, some testing data on the determination of the undrained shear strength of a residual soil in Singapore are presented. Large blocks of undisturbed residual soil samples were taken from a construction site of the Deep Tunnel Sewerage System Project in Singapore. To study the inherent strength anisotropy, specimens cut in both vertical and horizontal directions were tests. The anisotropy behaviour of intact residual soil was also investigated under different major principal stress directions. The tests conducted included K0 consolidated undrained triaxial compression (CK0UC) and extension (CK0UE) tests, and K0 consolidated undrained direct simple shear (CK0UDSS) tests. Based on the experimental results, the cu/s10¢ versus OCR relationships of each type of tests are established for practical applications. The failure envelopes and friction angles determined from different types of tests are also compared.