Thermo-mechanical coupling in landslide shear zones: from laboratory characterisation to slope-scale modelling under climate change

Our research investigates the complex thermo-mechanical coupling within landslide shear zones, specifically focusing on how temperature variations influence the residual shear strength of clayey soils. This parameter is a critical determinant for the stability of reactivated, slow-moving landslides.

In our laboratory investigations, we utilised a modified ring-shear apparatus equipped with a temperature-control system to conduct heating-cooling cycles (typically between 20 °C and 70 °C) on various soil samples. We have tested materials ranging from low-plasticity mountain soils to high-plasticity marls and bentonites. Our findings reveal that the thermal response of soil is sensitive to both mineral composition and rate of shearing.

Regarding slope modelling, we developed numerical frameworks, utilising finite-element analysis, that incorporate temperature-dependent failure criteria. By simulating scenarios from the 1960s to the 2060s based on historical and projected climate data, our results suggest that gradual ground warming may increase the factor of safety in certain clay-rich slopes, potentially transitioning active landslides into long-term dormancy. We also quantified the nonlinear coupling between temperature variations and groundwater table fluctuations, demonstrating that their combined impact on stability is more significant than the sum of their individual effects.

Our field monitoring and regional activities involved extensive sampling at disaster-prone sites and the calibration of thermal parameters using historical meteorological data to accurately reproduce ground temperature profiles. Furthermore, we have implemented spatial probability analyses at a national scale, utilising soil composition and topographic data to map expected changes in slope stability under global warming scenarios.

In the future, we plan to incorporate the soil-vegetation-atmosphere nexus into our framework. By evaluating how vegetation and root systems modulate heat and moisture fluxes, we should be able to capture the thermo-mechanical behaviour of the shallow subsurface more accurately. Additionally, we intend to expand our experimental investigations to a broader range of soil compositions and refine testing protocols to objectively assess the thermal sensitivity of landslide-prone formations.