Damage of Sandstone Induced by Repetitive Impact Loading

Abstract

The dynamic weakening of rock is frequently observed when the rock is subjected to a series of repetitive impact loads. Sandstone is utilized in our experiment on the dynamic performance under impact loading. The split Hopkinson pressure bar system with a confining pressure device is used for the experiments. Observations on strain waves recorded by a transmission bar indicate that sandstone demonstrates an evident nonlinear response under impacting loads which accompany a dynamic weakening effect. To quantify the damage induced by impact loads, we introduce a damage factor to study the weakening degree induced by impact loading and determine that sandstone breaks when the damage factor exceeds 0.52. Detailed statistics on the broken characteristics of the explored sandstone samples show that the damage evolution mainly extends along the maximum shear stress face, thus resulting in shear failure. Based on nonlinear wave propagation theory, we determine a shock wave distance for the explored sandstone. Result shows that the shock wave distance is larger than the sample length. Moreover, from a uniaxial compression test on specimens after impact tests, we found that failure patterns develop from split failure to shear slip failure with the increase in damage factor. Moreover, experimental observations comprise numerous dynamic regimes which can be extended to other granular rocks.