Effect of Loading Rate and Water on the Dynamic Fracture Behavior of Sandstone under Impact Loadings

The moisture content of rocks in nature often changes with the natural hydrological environment, and generally natural rock may be classified into three types, that is, dry, natural, and saturated rock. The corresponding responses to dynamic loads may have considerable difference, and therefore, impact tests in this paper were conducted on single cleavage triangle sandstone specimens with three types of conditions, respectively, under various loading rates. The ingredient of sandstone was determined by X-ray diffraction and optical microscopic image. The crack propagation parameters were recorded with the aid of a crack propagation gauge. The dynamic stress intensity factors were calculated using ABAQUS code. The results show that the fracture toughness of all the three types of specimens increase with loading rate, which could be expressed by power functions. Compared with dry and natural sandstone, the crack propagation speed of saturated sandstone specimens is more sensitive to the loading rate. Both the rate effect and the water effect, including water-weakening effect and water-enhancing effect, play a significant part in rock dynamic fracture behavior.