Abstract
Shear strength characteristics of soft Madinah clay have been investigated from a series of consolidated undrained (CU) direct shear tests on specimens without and with circular sand drains of variable diameters. The investigation is conducted to study the shear strength behavior of soft Madinah clay in the presence of sand drains provided for the purpose of accelerating drainage and enhancing its response towards stabilization by preloading. The experimental shear strength test results have been compared with the theoretical values based on shear strength of clay-sand composite material derived from the shear properties of the individual materials. The shear strength parameters obtained from this study are expected to be of benefit and practical use for carrying out stability analysis of structures like embankments and foundations supported by clay and stabilized with vertical sand drains. Useful data were obtained showing a positive influence of the sand drain system on the enhancement of shear strength characteristics of soft Madinah clay.