Innovative testing technique of rock subjected to coupled static and dynamic loads

A new testing technique, which relates the physical stress state of rock subjected to simultaneous coupled static and dynamic stresses, is presented. The method involves modification of a split Hopkinson pressure bar, such that the test specimen is subjected to coupled axial static pre-stress, axial impact loading, and optional confining pressure. Tests on siltstone specimens with different coupling loads showed that the strength of the specimens under coupling loads was higher than their corresponding individual static or dynamic strengths. In the grade size distribution, the percentage of small size particles of fractured specimen increases with higher coupling loads. The strength of rock under coupling loads decreases rapidly when the axial pre-compression stress is greater than 70% of the static strength of rock (with identical impact loading). However, with constant axial pre-compression stress and increasing impact loading, the strength of siltstone increases initially and reaches a maximum constant value.