Effect of spatial variability of soil properties on slopes stability under rapid water drawdown conditions

Resumo

Stability analysis of slopes is a fundamental problem of Soil Mechanics. Its main objective consists of evaluating the potential failure of the slope structure under a prescribed loading mode. A major component of the latter refers to the seepage forces induced by pore-pressure gradient, which is known to be responsible of destabilizing effects. This contribution employs a kinematic approach of limit analysis theory to obtain upper-bounds solutions to the stability problem of saturated slopes submitted to rapid water level drawdown. Random fields are used to model the uncertainty surrounding the spatial distribution of soil cohesion, friction angle, and permeability. In the context of effective stress governing the strength capacities of the soil material, it is shown that the seepage forces related to the water flow regime can be considered as external volumetric loads in the assessment of stability. The hydraulic problem governing the water filtration velocity is evaluated by resorting to an analytical variational approach, whose results are validated by comparisons with finite element solutions. The impact of hydraulic-related parameters on stability is first investigated for slopes within a deterministic framework. Subsequently, random fields are considered to take into account the variability related to the spatial distribution of the material properties, which are discretized using the Karhunen-Loève expansion with numerically computed eigenfunctions. The failure probability of slopes is assessed through Monte Carlo simulations. Several analyses have been performed to discuss the influence of the spatial variability of relevant problem parameters.