Abstract
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.
Highlights
In both above-ground rock structures with large temperature differences between day and night and underground rock engineering such as geothermal energy engineering, underground coal gasification and radioactive waste disposal, rocks as the main load-bearing material can be subjected to extreme conditions involving high temperature [1,2,3,4,5,6,7,8,9] and weathering [10,11,12,13]
Porosity, and P-wave velocity are important parameters of petrophysical properties. Testing these parameters is of positive significance for measuring the damaging effect of thermal shock (TS) on the integrity of the rock matrix [35]
The evolution pattern of these parameters with the variation of heating level and cooling rate is analyzed based on the test results
Summary
In both above-ground rock structures with large temperature differences between day and night and underground rock engineering such as geothermal energy engineering, underground coal gasification and radioactive waste disposal, rocks as the main load-bearing material can be subjected to extreme conditions involving high temperature [1,2,3,4,5,6,7,8,9] and weathering [10,11,12,13]. Sudden changes in temperature can cause thermal stress and “catastrophic damage in the form of cracks so that the strength of the material is suddenly decreased” [14]. This process is referred to as thermal shock (TS) [14,15,16]. Analyzing the impact of the TS process on the dynamic mechanical properties of the rock is essential for the structural stability and safety design of rock engineering both aboveground and underground
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