Discussion: A new analysis procedure to explain a slope failure at the Martin Lake mine

Abstract

The Authors utilize the upper bound (kinematical) approach of limit analysis to evalu-ate the stability of slopes, taking into account the pore pressure in the soil mass. They have devel-oped a failure mechanism which includes both rigid rotation and shear deformation (plane strain). However, I cannot agree with the Authors' method of calculations. In particular, it will be argued that the calculations of the energy dissipation rate in the plastic deformation process are incorrect. The Authors consider soil whose skeleton obeys the Mohr-Coulomb yield condition and the flow rule associated with this condition. Accord-ingly, the yield condition is expressed in terms of the effective stress tensor components crij' f(aij') = 0 (38) and the associative flow rule Eij = @f/&rij'), 1 2 0 (39) defines the rate of deformation of the skeleton tij under the effective stress state satisfying equation (38). In the process of plastic deformation of the soil skeleton, the rate of energy (or work) dissi-pation per unit volume is given by the dot product of the effective stress tensor and the strain rate tensor d = Uij'lij (40)