Shear strength characteristics of statically compacted unsaturated kaolin

Abstract

The shear strength characteristics of statically compacted unsaturated soil specimens of commercial kaolin (Ip= 15%) were determined using conventional triaxial shear testing apparatus extending total stress analysis. The testing program consists of two different types of confined compression shear strength tests on unsaturated soil specimens. In the first series of tests, the specimens were sheared immediately after the application of the confining pressure under undrained loading conditions. In the second series of tests, the specimens were first allowed to come to equilibrium with respect to volume change and suction value under the applied confining pressure and sheared at two different rates of strain. A psychrometer was used for measuring suction values. In addition, conventional consolidated undrained tests were also conducted on specimens that were saturated using the back pressure technique before shearing. Comparisons with respect to the shear strength behavior are provided for both saturated and unsaturated soil specimens. The shear strength contribution towards suction was determined from test results on unsaturated soil specimens extending state variable approach in terms of total stresses. Discussion is presented to understand the influence of the following factors (i) suction, (ii) confining pressure, and (iii) rate of strain on the shear strength.