Numerical simulation on rock failure under combined static and dynamic loading during SHPB tests

The failure process of rock subjected to combined static and dynamic loading constitutes the mechanism of many engineering applications such as rockburst prediction, rock fragmentation, as well as rock drilling and blasting. In this study, the basic principle for simulating the damage and failure process of rock under combined static and dynamic loading is introduced, and it is implemented into RFPA-Dynamics (Rock Failure Process Analysis for Dynamics), a finite element package to analyze the failure process of rock-like media subjected to dynamic loading. The extended RFPA-Dynamics code is firstly validated by simulating the stress distribution and damage evolution in rock specimens during conventional SHPB (Split Hopkinson Pressure Bar) tests. Then, it is utilized to simulate the failure process of rock under combined static and dynamic SHPB tests, and the effects of axial static stress and dynamic stress on the damage and failure process of rock are examined. The strength increase factor (SIF) under combined static and dynamic loading, depending on the rock heterogeneity, static stress and strain rate, is predicted using numerical simulations, and the mechanisms associated with the increase of dynamic strength of rock subjected to the combined static and dynamic loading are clarified. The rock strength predicted with numerical simulations, which is closely related to the rock heterogeneity, is in qualitative agreement with that observed in laboratory SHPB tests, although the predicted rock strength under combined static and dynamic loading is still lower than those from experiments.