Direct and Simple Shear Testing of Two Canadian Sensitive Clays
Several series of consolidated undrained direct translatory shear (DTS) and direct simple shear (DSS) tests have been performed on two sensitive clays of eastern Canada. Before shearing, the specimens were consolidated to pressures varying between 20 and 350 kPa. The investigation was performed with the aim of determining both the anisotropic nature and the effect of the consolidation pressure level on the response of the tested clays. To study the anisotropic nature of the sensitive clays, the specimens were cut at various inclination angles with respect to the in-situ horizontal plane, consolidated to predetermined normal stress levels, thus altering the fabric, and then sheared under undrained conditions. The range of the normal stress levels used was such as to be able to investigate the response of the soil from very high overconsolidation ratios to normally consolidated or destructured states. The results show that for consolidation pressures less than the preconsolidation pressures of the inclined specimens, the undrained shear strengths are anisotropic. In this case, the specimens that are sheared along the horizontal in-situ direction show the lowest strength, while those that are sheared along the vertical in-situ direction have the highest strength. However, for the specimens that are consolidated under pressures in excess of the preconsolidation pressures, the undrained shear strengths are found to be independent of shearing direction.