An experimental study on the shear strength behaviour of an interlayer shear weakness zone

Abstract : In order to evaluate the overall stability of the underground powerhouse at the proposed Baihetan hydropower station in China, the shear behaviour of a weak interlayered soil in the host rock and the soil/host rock interface was investigated in the laboratory by direct shear testing under different degrees of saturation. Shear creep tests were also undertaken on the interlayered soil. Typical results obtained from the multi-sample method (MSM) and single-sample method (SSM) are presented, which show that the shear behaviour of both the interlayered soil and the soil/rock interface is elastic perfect-plastic without dilatancy. It was not possible to determine the shear strength parameters using the multi-sample method due to the heterogeneity of the interlayered soil in terms of mineralogical composition and physical properties. Creep of the interlayered soil was found to be insignificant. The shear behaviour of the soil/rock interface depends strongly on the interface morphology: the rougher the interface the higher the shear strength. (English) [ABSTRACT FROM AUTHOR]