This paper attempts to elucidate the mechanism of failure in rate-independent granular materials using the discrete element method. For this purpose, the dynamic response of dense and loose specimens has been simulated over drained and undrained loading paths. Then, this paper revisits the relation between the occurrence of an outburst in kinetic energy with the second-order works evolution. It is shown that the prediction of the evolution of the specimen’s kinetic energy over time, according to the second-order work approach, is satisfactorily verified by the discrete numerical simulations. In particular, the conflict between external and internal second-order works is shown to play a basic role during the failure process.