Dynamic Properties of Thermal Shock Treated Sandstone Subjected to Coupled Dynamic and Static Loads

In deep rock engineering, the rock mass can be subjected to thermal stress caused by sudden changes in temperature, which is referred to as thermal shock (TS). To study the effect of TS on heated sandstone, three cooling methods are used to provide different cooling rates. Then the coupled dynamic and static loading tests are carried out on the heated sandstone by means of a modified split Hopkinson pressure bar (SHPB) system. The test results show that as the heating level increases, the dry density, P-wave velocity, and the dynamic combined strength of the heated sandstone decrease, while specimen porosity increases. Particularly, a sharp change in the physical properties of sandstone can be observed at 650 °C, which is believed to be caused by the α-β transition of quartz at 573 °C. At each heating level of the test, the damage caused by the higher cooling rate to the heated sandstone is more than that caused by the lower cooling rate. The different failure modes of sandstone with increasing temperature are analyzed. The mechanism of TS acting on heated sandstone is discussed, and two typical fracture patterns reflecting the action of TS are identified through SEM.