Study On The Constitutive And Mechanical Properties Of Granite Under The Action Of Thermal-mechanical Coupling Cycle

At present,China has built a relatively complete clean energy production chain,especially in the utilization of hot dry rock.Hot dry rock geothermal is a kind of renewable clean energy with special advantages.This kind of geothermal exchange energy is also the key to promote the transformation of China ’s energy structure and low-carbon development.However,there are still some deficiencies in its development.The main reason is that this kind of geotechnical engineering is located in the underground rock mass.The surrounding rock is generally affected by high temperature and high stress,and the rock is in different temperatures and different stress states.Therefore,it is particularly important to deeply explore the mechanical characteristics and deformation damage of deep rock mass under the action of stress,high temperature and mining disturbance.In this context,researchers have carried out many discussions and studies on the mechanical properties,cyclic loading and unloading conditions,failure characteristics and constitutive models of rock at different temperatures.Therefore,this paper analyzes the uniaxial test data of granite after different temperature treatment.The periodic loading-unloading test data are fitted with the rock damage constitutive model,and the parameters in the model are analyzed.The physical properties of granite at different temperatures were analyzed.The results show that :(1)Temperature has a significant effect on the apparent,volume,mass,density and wave velocity of granite,and temperature is an important factor affecting the physical properties of rock.The higher the temperature,the more serious the damage of rock.(2)Through the conventional uniaxial and periodic loading-unloading tests,it is obtained that the stress decreases with the increase of temperature,and the strain increases with the increase of temperature.However,compared with the uniaxial test,the ultimate stress of the periodic loading-unloading test is reduced to a certain extent.The reason is that the granite samples have different degrees of damage during the periodic loading-unloading test.(3)According to the mechanical damage of granite,it is assumed that the failure of rock element obeys Weibull formula.Based on Griffith strength criterion,the damage constitutive equation of granite under cyclic loading and unloading at high temperature is established.The thermal-mechanical damage constitutive model is established by using the formula,which provides a reference for the study of damage constitutive of rock materials.(4)The loading-unloading test data were compared with the thermo-mechanical damage constitutive model by curve fitting,and the fitting correction coefficients were all above 0.99,and the fitting situation is ideal,which verifies the rationality of the thermo-mechanical coupled rock damage constitutive model.The parameters and m are discussed,and the specific physical meaning of the parameters is analyzed : the parameters are affected by the average strength of the rock,and the distribution of rock micro-element strength affects the value of the parameterm.Figure [35] Table [10] Reference [94]...