Investigating the softening of weak interlayers during landslides using nanoindentation experiments and simulations

Based on nanoindentation experiments and numerical simulations, an approach is developed to investigate the softening of weak interlayers, which might trigger landslides. The components of weak interlayers in natural slopes are mainly rock fragments and clay, which lead to the difficulty of preparing intact samples for traditional rock mechanical experiments. Additionally, most rock slopes are microsensitive fractured geological media. The slope failures are significantly influenced by the anisotropic and rheological mechanical evolution of weak interlayers, which is strongly related to their microstructure. In this work, the shale in weak interlayers is investigated using nanoindentation experiments, so the experimental samples can be very small and possess arbitrary shapes. The experimental results at the microscale are upscaled using the Gaussian mixture model and Mori-Tanaka scheme, which are then used in numerical modeling to investigate the failure of a slope in southwestern China. According to the results, after water immersion, the friction angle of shales is almost constant, while the elastic modulus and cohesion decrease significantly. The shear strength of weak interlayers decreases significantly so that the plastic zones develop along the weak interlayer, which leads to landslides.