Limit load in translational failure mechanisms for associative and non-associative materials

Translational failure mechanisms for estimation of the limit load in geotechnical boundary-value problems are considered. The equivalence of the energy balance approach and the equilibrium of forces approach for limit load evaluation in this type of failure mechanism is studied in detail. The soils are modelled as rigid-perfectly plastic materials with flow rules associative and non-associative to a linear Mohr-Coulomb yield condition. It is demonstrated that for non-associative materials with a coaxial flow rule, the limit load in translational failure mechanisms corresponds to a fully developed residual strength due to non-associativeness, and is lower than the limit load for the associative material. However, the limit load for nonassociative materials with a non-coaxial flow rule may be the same as for the associative material. Implications for the interpretation of one of the limit equilibrium methods are discussed.