Analysis Of Damage Evolution And Fracturing Effect Of High Temperature Granite Under Different Cooling Shocks

Temperature has a significant effect on the thermal damage of rock,such as in-situ gasification of underground coal mining,tunnel fire sprinkler,EGS extraction,high temperature rock subjected to cooling shock induced cracking damage.Therefore,it has important research value and guidance to carry out the study of cooling shock damage and fracture of high temperature rocks under the action of large temperature difference.At present,the relevant research is mainly focused on the damage and cracking of high-temperature rock,but there are relatively few studies on the evolution of physical and mechanical properties and cracking effect of high-temperature rock under cooling shock.Therefore,taking high-temperature granite as the research object,this paper studies the cracking effect of different cooling shocks on high-temperature granite by means of theoretical analysis,cooling shock test and numerical calculation.Comparing the difference characteristics of physical and mechanical properties of high temperature granite after different cooling shocks,the crack evolution pattern and fracture mechanism are explored.The main research work is as follows:(1)Analysis of temperature change and cracking effect of porous granite under different cooling shock conditions;taking porous granite as an object,before and after rapid cooling shock under different high temperature,the changes of physical properties and cracking conditions such as apparent color,cracking condition and crack shape of granite are studied,and the temperature change law of high temperature rock during cooling shock is tracked and analyzed.Based on the analysis of microstructure changes of high temperature granite after different cooling shocks by micro digital electron microscope,quantitative statistical analysis of crack morphology and extension mode is carried out to explore the temperature threshold of significant cracking changes induced by cooling shock,and then to clarify the universal law of cracking evolution of high temperature granite induced by cooling shock.(2)Numerical simulation analysis of cracking evolution of high temperature granite induced by cooling shock;based on the results of laboratory tests,a numerical model is established to simulate the cracking of high temperature granite under different cooling shocks,and the RFPA numerical simulation program is used to simulate and analyze the cracking process and effect of porous granite under different cooling shocks.The data support is provided for a better explanation of the mechanism of cooling shock cracking,and the deviation between simulation and test results is analyzed.(3)Analysis of damage evolution characteristics of high temperature granite under different cooling shock conditions,test the wave velocity and apparent resistance parameters of granite after different cooling shock,and make clear the difference law caused by different cooling shock.Combined with uniaxial compression and acoustic emission testing tests,the change characteristics of mechanical parameters of granite after different cooling shock are obtained,and the damage evolution characteristics of high temperature granite under different cooling shock conditions are summarized.(4)Combining the test results with theoretical analysis,based on the category of rock mineralogy,from the perspective of thermodynamics and mineralogy,this paper probes into the cracking evolution mechanism and mechanical damage mechanism of granite caused by different cooling shock,and reveals the internal relationship between cooling shock on granite from meso-damage to macro-mechanical damage.