Study On Physical And Mechanical Properties Of Jointed Granite After High Temperatures

In this paper,based on the research background of high temperature jointed rock mass damage,such as the development of deep ground resources,the utilization of underground space,the evaluation and repair of tunnel fire,the deep buried geological treatment of nuclear waste and so on,through the joint granite test after high temperature action,the research on the physical and mechanical properties of jointed granite is carried out by the heating/cooling rate,and the joint rock mass with heating/cooling mode and joint types are analyzed.The damage evolution equation of jointed granite under the thermal and mechanical coupling is established,and the thermal damage evolution process of mechanical properties of jointed granite is discussed.The main studied results are as follows.(1)High temperature causes the change of physical and mechanical properties of granite.Especially when the temperature is higher than 400 ?,the physical and mechanical properties of granite change rapidly.The change rate of physical and mechanical parameters of granite under the condition of water cooling is larger than that of granite under the condition of natural cooling,especially the influence on surface crack width,density and fractal characteristics,cumulative ring count,peak strain,peak strength and brittleness.(2)At the same temperature,the uniaxial compressive strength of jointed granite is higher than that of jointed granite;the uniaxial compressive strength of jointed granite increases with the increase of the angle ? between the joint and the maximum principal plane;the peak strength and cumulative acoustic emission ring count of conjugate jointed granite are slightly more than those of echelon jointed granite.(3)Before 600 ?,there are mainly three fracture fissures after the failure of conjugated joint granite,and all of them are tensile fissures,while there are two fracture fissures after the failure of echelon joint granite,which are tensile fissures and shear fissures respectively;above 600 ?,most of the granite is plastic failure,and most of them are powder like in the fracture zone,and there are two fracture fissures after the failure of conjugated joint granite which are mostly tensile fractures,while the echelon jointed granite mainly produces a fracture along the joint direction after failure which are mostly shear fractures.(4)With the increase of heat treatment temperature,the initial damage of granite increases gradually after high temperature.With the increase of axial strain,it shows a steep dip angle rise at lower temperature,while the damage variable curve tends to be gentle at high temperature.In addition,the initial damage of granite under water cooling is higher than that of natural cooling.There are 65 figures,5 tables and 143 references in this paper.