Study On Physical And Mechanical Properties Of Granite Under Thermo-mechanical Coupling

In the deep geological disposal of nuclear waste,the rock is in the multi-field coupling environment of stress field,heat field,seepage field and chemical field.The study of the physical and mechanical properties of the rock under the coupling of multiple fields is the basis and scale for analyzing the long-term stability of the rock.The study of the multi-field coupling problem of rock is often very complicated.The simulation of indoor experiment has some guiding significance to the deepening of practical engineering.On the other hand,this article also takes into account the current new energy project-dry hot rock engineering,in the indoor simulation test will experience high temperature heating granite samples quickly cooling into cold water,taking into account the actual work of dry and hot rock condition.In this paper,the physical and mechanical properties of granite under thermal-mechanical coupling conditions are studied.The influence of heat treatment temperature on the development of thermal fissures is analyzed by changing the wave velocity,thermal conductivity,permeability,mechanical parameters and strength parameters of granite after rapid water cooling.And make a theoretical analysis of this effect.The specific conclusions are as follows:1.The porosity and permeability of the granite increased with the heat treatment temperature,and the heat conduction coefficient and the acoustic wave velocity decreased gradually;2.X-ray diffraction and SEM scanning electron microscopy(TEM)show that the thermal fissures are not developed when the heat treatment temperature is less than 200 oC.When the heat treatment temperature is in the temperature range of 200 ~ 500 oC,the micro-temperature fissure occurs.When the heat treatment temperature is higher than 600 oC,The thermal fissure appears longer length,there cross-through;3.The triaxial compressive strength of granite decreases with the increase of heat treatment temperature under the same confining pressure condition after high temperature water cooling,and the failure form changes from brittle failure to ductile failure;4.The long-term rheological test shows that the higher the heat treatment temperature,the more obvious rheological properties.