Finite element analysis of two landslides with the second order work criterion

Abstract : The recent emerging idea of incorporating bifurcation criterion based on the second order work into finite element codes has triggered the development of pertinent criterion that allows to analyse landslide mechanisms. Starting with homogeneous stress-strain fields, the bifurcation domains of sands in plane strain conditions are studied through strain proportional paths and by using the incrementally piece-wise linear (octolinear) constitutive model. The boundaries of the bifurcation domain and the unstable stress directions are determined by considering the sign of the second order work. The results show that for strong non-associated materials as soils, these unstable stress-strain states can be reached strictly inside the plastic limit condition. These analysis are then extended and applied to complex boundary problems solved by the finite element method. Two real cases of landslides, which occurred on the Trévoux hillside (France) after an intense rainfall period in 1983 and at Las Colinas (El Salvador) under earthquake shaking in 2001, are simulated by using the finite element codes LAGAMINE and PLAXIS, respectively.