Mechanical Properties and Microscopic Failure Process of Exemplary Argillaceous Interlayer from East China

The landslide disaster caused by the argillaceous interlayer not only destroys buildings, cultivated land, and roads but also seriously endangers human life and safety. This study concerns the mineral composition of selected argillaceous interlayer and their strength characteristics. To study the mineral composition of argillaceous interlayers, 8 kinds of samples in the southern Jiangsu region of China were analyzed utilizing X-ray diffraction (XRD). The repeated direct shear strength tests (RDST) were carried out on the undisturbed specimens of the argillaceous interlayer. The results show that the argillaceous interlayer with high content of kaolinite shows ductile failure mode, which means that there is no obvious residual strength in the shear process. The arrangement of mineral particles on the shear surface of the specimens after different shear displacements was observed under the scanning electron microscope (SEM). It was observed that mineral particles on the shear surface showed a more directional arrangement with the increase of shear displacement. Furthermore, the influence of shear direction on the argillaceous interlayer with completely oriented mineral particles was studied through numerical experiments with four shear strength mechanisms proposition proposed. The influence of the mineral arrangement on the action occasion and magnitude of dilatancy component of shear strength is clarified in the shear mechanism.