The strength changes and failure modes of high-temperature granite subjected to cooling shocks

Granite at a high temperature can cause a decrease in strength and cracking when exposed to a rapid cooling shock. Therefore, the cooling shock method can be considered as a potential cracking technology to improve the energy exploitation efficiency. The thermal cracking damage of high-temperature granite after cooling shock induced by different low-temperature refrigerants were studied. Firstly, granite samples were heated to different targeted temperatures (i.e.100, 300, 500, and 700 degrees C). Then, all heated samples were respectively soaked in these refrigerants with different temperatures (i.e. 20, 0, - 10, - 20 and - 30 degrees C) or cooled in the air condition as a reference. When the cooling process ends, the effects of cooling shock on the strength characteristics and failure modes of high-temperature granites were respectively observed by acoustic wave, uniaxial compression test and the acoustic emission (AE) test. Some main conclusions are: (1) The high temperature granite p-wave velocity tends to decreases with the refrigerant temperature decreases. (2) The lower CaCl2 solution temperature is, the lower the peak strength. The specific performance is that the higher granite temperature, the more obvious the granite strength decreases after the cooling shock. (3) The curves under different temperature gradients performs from a single/double peak to a multipeak as the refrigerant temperature decreases. (4) The failure modes of granite subjected to different temperature gradients are obviously different, of which X-type shear failure is shown above 500 degrees C. These studies verify the strong effect of cooling shocks on high-temperature granite. Scholars can draw on the experience of cooling shock technology in the geothermal development of late-stage high-temperature rock masses.

Automated summary

This study investigates the effect of cooling shocks on high-temperature granite by inducing cooling shocks with different temperature refrigerants. The results show that the refrigerant temperature has a significant impact on the strength and failure modes of the granite, providing practical experience and references for geothermal development.