Experiment study of physical and mechanical properties of sandstone after variable thermal cycles

To study the effects of temperature cycles on the mechanical properties, thermal damage, and fracturing of sandstone, uniaxial compression tests and Brazilian splitting tests were performed using a hydraulic pressure servo rigidity rock mechanics experiment system. Before the tests, the sandstone samples were treated with cyclic (repeated from 0 to 8 cycles) temperatures from 100 to 600 °C. In addition, the chromaticity (color parameters L*, a*, and b*), thermal conductivity, and P wave velocity of the sandstone samples were measured using a color meter, thermal conductivity tester, and acoustic wave detection device, respectively. The results show that the peak strength, tensile strength, thermal conductivity, and P wave velocity decrease rapidly when the samples are exposed to higher temperatures (> 400 °C). Below 300 °C, the decrease is mainly due to the escaping of the adhered, bound, and structural water. Between 300 and 600 °C, the thermal response of the minerals in sandstone increases the development of microcracks and weakens the sandstone. At these same temperatures, when the number of cycles increases, the peak strength and tensile strength of the sandstone decrease, which is more obvious at higher temperatures. After multiple cycles, the plastic characteristics of the sandstone increase. The results obtained in this paper are good for predicting the thermo-physical properties of sandstone when exposed to high temperatures.