A unified approach for analysing surface flow and groundwater induced slope instability

Abstract

ABSTRACT The combined effects of transient, surface and subsurface flows and infiltration govern the rainfall-induced potential failure of unsaturated soil slopes stabilised by matric suction. In this paper, it is shown how fundamental fluid dynamics can be employed to closely model the above flow effects than the empirical Richard’s approach. The fluid dynamics-based Navier-Stokes formulation also facilitates the integration of the three modes of flow: (1) surface, (2) subsurface and (3) infiltration water flows, into a unified analytical model. Therefore, in contrast to previous studies, this fundamental approach can seamlessly incorporate the effects of continuous interplay between surface and subsurface water flows and the inertial terms of flow on the reduction of matric suction in unsaturated soils. Transient flow effects have been combined with geomechanics of unsaturated soil to demonstrate their impact on the stability of an embankment under a more realistic non-uniform rainfall. The innovative use of the laboratory-evaluated soil properties such as the hydraulic conductivity and porosity to express the drag force in the Navier-Stokes equations facilitates the examination of the sensitivity of slope stability to the relevant soil classification parameters.