Thermal Damage and Energy Characteristics of Sandstone under Real-Time High Temperatures

Liao Anjie; Zhang Yan; Wang Fei; Ma Yu

doi:10.3799/dqkx.2023.206

Abstract：The damage and energy evolution characteristics of rocks under real-time high temperature are hot and difficult issues in deep geological engineering.MTS815 program-controlled servo rigid testing machine and PCI-II acoustic emission instrument were used for triaxial compression tests of sandstone under real-time high temperatures in this study,and the mechanical and energy characteristics of sandstone under high temperature were analyzed and discussed based on the test results and introducing the law of energy consumption evolution.The results show that:(1)There is a temperature threshold between 120 ℃ and 150 ℃,which leads to thermal damage inside sandstone,and its peak strength is greatly reduced,and the macroscopic failure form is transformed from shear failure to tensile failure.(2)When the temperature is between 20 ℃ and 120 ℃,the accumulated AE energy,stored energy and released energy of sandstone increase with the increase of temperature;and when the temperature is 150 ℃,thermal damage occurs inside sandstone.Ac cumulative AE energy,energy storage capacity and energy release capacity were significantly reduced.(3)The brittleness index of rock BE decreases with the increase of temperature.At the temperature of 120-150 ℃,the sandstone BE value decreases greatly from about 0.5 to 0.26,showing obvious plastic characteristics.The influence of temperature on the mechanical properties,failure mode,acoustic emission activity,strain energy evolution process and brittle state of sandstone is systematically analyzed.It is found that there is an obvious temperature threshold,which changes all kinds of behaviors of sandstone obviously before and after the threshold.