Undrained Shear Strength Anisotropy of Normally Consolidated Cohesive Soils

Abstract

ABSTRACT In order to investigate the undrained shear strength anisotropy of cohesive soils of intermediate grading between sands and clays, a series of consolidated undrained triaxial compression and extension tests is performed on soil samples which are prepared by mixing Kawasaki clay and Toyoura sand (with crushed fraction) so as to obtain a wide range of soil type expressed in terms of plasticity index Ip. Four kinds of cohesive soil samples with Ip of 30, 20, 15 and 10 are tested. The conclusions from this study are: 1) Undrained shear strength anisotropy increases with decrease in Ip. And difference between values of (cu/p)E/ (cu/p)c obtained by CIU and CK0U tests increases as the plasticity index increases. 2) Relationship between cu/p values obtained by four types of consolidated undrained triaxial tests and Ip is quantitatively shown. 3) In view of either shape of effective stress paths and the undrained shear strength anisotropy, shear properties of cohesive soils of Ip of 20 and 30 are seen to be those of clays, however, soils of Ip of 15 and 10 are considered the intermediate soils. Based on results of the present study, a way of accounting for the anisotropic undrained shear strength in stability analysis is proposed, with assumption that the in situ undrained compression strength of vertical sample is known.