EXPERIMENTAL STUDY ON INFLUENCE OF CONTACT ANGLE ON SHEAR STRENGTH OF INTERFACES BETWEEN LOESS AND HIPPARION RED CLAY

Loess is widely deposited on the Hipparion red clay and forms weak interfaces,which is a typical slippery layer in northwest China. To investigate the influences of interface contact angle on shear strength characteristics of interfaces between loess and Hipparion red clay,we performed a series of direct shear experiments using a home-developed shear equipment. The results indicate that the failure modes of interfaces between loess and Hipparion red clay can be divided into sliding,sliding and shear-off,and cutoff. The interface contact angle affects the failure mode of interfaces. When the interface contact angle of interface is larger,the failure mode tends to be cutoff. When the interface contact angle of interface is smaller,the failure mode tends to be sliding. The shear stress-displacement curves of interfaces show that the shear failure characteristics of interfaces are brittle obviously. As the interface contact angle of interface increases,the shear stiffness and shear failure displacement of interfaces increase,and the "dropping" phenomenon of shear stress-shear displacement curves becomes more obvious. The dilatancy effect of interfaces is obvious in the shear process. The peak dilatancy angle of interfaces decreases first and then increases with the increasing interface contact angles,which reflects the different shear failure modes of interfaces. The shear strength of interfaces varies nonlinearly with the normal stresses and interface contact angles. The peak strength of interfaces increases first and then decreases with the increasing interface contact angles,and the variation range of peak strength increases with the increasing normal stresses. The residual strength of interfaces increases with the increasing interface contact angles,and the variation range of peak strength increases with the increasing normal stresses.