Experimental Study on the Acoustic Emission Characteristics of Fractured Granite after Repeated High Temperature-Water Cooling

Abstract

Using the MTS816 rock mechanics servo tester, an acoustic emission monitoring system and high-speed digital photographic equipment, uniaxial compression tests were conducted on granite specimens containing single fracture slabs after repeated treatment (treatment times 1, 5, 10, 15 and 20) with three types of high temperature (250, 350 and 450 °C) water cooling, respectively, to analyze the basic mechanical parameters, acoustic emission change characteristics and fracture evolution of the specimens during the uniaxial compression process. It is shown that the heating temperature and the number of treatments not only have a deteriorating effect on the basic mechanical parameters of the specimens but also have an important effect on the changes in the basic parameters of acoustic emission at different compression stages. At 250 °C, the acoustic emission characteristics of the specimens at the initial tightening stage tended to decrease (N = 1 and 5 times) then, increase (N = 10 and 15 times) and then decrease (N = 20 times) as the number of treatments increased. At the same set temperature, the percentage of the bottom amplitude value of the acoustic emission of the specimen gradually decreases, and the percentage of the high amplitude value gradually increases as the number of treatments increases. After the specimen undergoes one and five treatments at 250 °C, the maximum acoustic emission energy value changes less, the maximum acoustic emission energy value decreases with the increase of treatment times in an approximately exponential function, the specimen is transformed from the brittle damage mode to the plastic damage mode and the effect of the prefabricated fracture on the damage of the specimen gradually disappears.