Effect of temperature as well as heating and cooling cycles on rock properties

Temperature has a significant role in many actions performed on rocks. An example would be the effect of temperature on rocks in the burial of nuclear waste, geothermal energy extraction, deep oil well drilling, and fires in tunnels. In addition, due to diurnal/nocturnal as well as seasonal temperature variations, rocks undergo a process of heating and cooling. In the present work, the effect of temperature as well as heating and cooling cycles on the rock properties was studied. The utilized samples included tuff, andesite, and sandstone. In addition to natural samples, concrete was also studied in this research work. The aim of this work was to evaluate the effect of temperature on the tensile strength of rocks and the velocity of longitudinal waves in a single heating and cooling cycle of samples as well as evaluating the effect of the number of heating and cooling cycles on the tensile strength of rocks and the velocity of longitudinal waves. In order to investigate the effect of temperature on the tensile strength of rocks as well as the velocity of longitudinal waves in a single heating and cooling cycle, the samples were heated in a furnace. After cooling the samples, the Brazilian and the sound velocity tests were carried out on them. These tests were conducted at the three temperatures of 100, 200, and 300 °C. In order to examine the effect of the number of heating and cooling cycles on the tensile strength and the velocity of longitudinal waves, the samples were heated up to the temperature of 100 °C and then cooled down in order to reach the room temperature. In this case, the work was conducted in the three modes of 5, 10, and 15 cycles. The test results showed that the velocity of longitudinal waves and the tensile strength of samples decreased but their porosity increased. Reduction in the tensile strength varied in different rocks so that the greatest and lowest reduction in the tensile strength was observed in concrete and andesite, respectively.