Executive Summary : | The PI proposes a new analytical and numerical framework to model the stability and mechanical behavior of natural failure planes in response to precipitation events. The framework relaxes the assumption of constant frictional strength used in geotechnical/geological landslide hazard estimates by using laboratory-derived, realistic constitutive equations for friction and soil hydro-mechanical properties. The PI argue that the classical, constant friction, Mohr-Coulomb failure criterion cannot explain recent observations that rainfall-induced landslides evolve to unstable failure over time scales. Instead, they propose using the rate-state friction (RSF) constitutive equations, which allow friction to evolve with displacement histories of landslides, providing an intrinsic time scale for shear strength variations independent of pore-pressure variations. The model also considers the coupling of soil porosity with shear deformation through soil dilatancy and infiltration of rainwater through unsaturated media with pore-pressure dependent hydraulic diffusivities. The PI propose to develop analytical stability criteria using linearized eigen spectrum analysis and Lyapunov functions, which can be directly used in producing physics-based landslide hazard estimates when provided with relevant laboratory-derived soil constitutive parameters. Additionally, the authors will develop numerical models that couple post-yield creep within basal zones of landslides to frictional sliding at the base, providing realistic simulations of landslide dynamics in response to precipitation events that can be validated against field observations. |