Water saturation effects on dynamic fracture behavior of sandstone

Abstract To understand combined effects of water saturation and loading rate on the fracture behavior of rock materials, dynamic notched semi-circular bending (NSCB) tests were conducted on dry and saturated sandstone specimens under a wide range of loading rates using a modified split Hopkinson pressure bar (SHPB) setup. Test results revealed that, the dynamic fracture initiation, propagation toughness and crack propagation velocity of saturated specimen were apparently lower than that of dry ones at the same loading rate. The above parameters increased with the increase of loading rate. Compared with the dry specimen, the saturated specimen owned a higher rate dependency of the dynamic fracture initiation, propagation toughness and a lower rate dependency of crack propagation velocity. Moreover, dual effects of water on the fracture behavior under different loading rates were discussed. It is believed that the different rate dependencies of fracture behaviors between dry and saturated specimens was governed by the combined weakening and enhancing effects of water. A micro-mechanical model was further developed to explain the experimental results based on the duality of water and linear elastic fracture mechanics (LEFM).