Modelling weathering-induced progressive rock slope failures

Rock slopes usually exhibit progressive failure phenomena over a long period of time under the active Earth surface environment involving complex geological, mechanical, hydrological, and chemical interactions. Among these processes, weathering has been recognised as a ubiquitous and important factor that drives slope destabilisation. Rock masses in a slope may experience weathering-induced strength degradation of variable degrees depending on the morphology, lithology, depth, fracturing, and time, which can lead to the emergence of various rock slope failure patterns, e.g. planar and rotational slides, slumps, topples, and rock falls. After failure, the slope may transition from slow deformation to catastrophic collapse characterised by rapidly moving material flows of fragmented rocks. These complex processes are driven by various mechanisms operating across different timescales, which pose a great challenge for modelling the entire history of rockslide evolution. In this study, we develop a unified computational framework for simulating the pre- and post-failure behaviour of rock slopes subject to long-term weathering processes. This framework includes the following key features: (i) a coupled weathering-damage model is developed to capture the interplay of weathering-induced strength loss and damage-related strain softening; (ii) pre-existing faults are represented explicitly as thin weakness zones; (iii) an implicit time integration scheme is adopted to simulate the slope evolutionary behaviour across multiple timescales; (iv) a frictional velocity-weakening law is incorporated to capture the development of rapid mass flows; (v) the particle finite element technique is used to track the small to large deformation/motion of rock masses. We show that our model can realistically simulate the pre-failure progressive rock slope destabilisation, the catastrophic rock mass failure, and the post-failure transient runout, demonstrating the capability of our model in realistically capturing the initiation, evolution, and consequence of weathered rock slope failures. Our results provide useful insights into the interplay of natural weathering and brittle damage in rockslide evolution and the control of geological structures on pre- and post-failure patterns of rock slopes.