Research On Damage Mechanism And Acoustic Emission Characteristics Of Red Sandstone Under Temperature And Loading

With the progress of the world and economy, energy becomes more and more important forhuman beings.Some engineering problems involving temperature often occur to us, such asthe engineering of exploiting geothermal resources and the engineering of burying nuclear waste.The mechanical properties of the rock under different temperatures attracted great attention frommany fields. To research the mechanical properties of the rock under high temperature is thepremise of effectively resolving the engineering problems of rock under the high temperature. Inthis paper we mainly studies red sandstone by using MTS810、MTS815Electro-hydraulic ServoMaterial Testing System and matched Acoustic Emission Detector, High Temperature Furnace,Microscope， Scanning Electron Microscope. With damage evolution laws, the fracturemechanism of the red sandstone that under different temperatures conditions are studiedsystematically from the macro to mesoscopic scales. We summarized the change laws of theacoustic emission signals with different temperatures and discussed the relation between the lawsand rock damage. The main works and research results are as follow:（1）We got whole stress-strain curves of sandstone samples at the temperature from20to900℃by means of experiment and the change laws of elastic modulus, peak strain, peak stress,peak strength with temperature increasing.（2）The real-time acoustic emission was recieved from red sandstone under hightemperature and loading. It indicated red sandstone showed thermal expansion effect under hightemperature, due to thermal expansion effect it generated weak acoustic emission signal, theacoustic emission signal was weak under low stress, but it became more active as the stressincreasing. So the activity of acoustic emission signal is closely related with temperature.（3）By using scanning electron microscope and microscope we got the photographs of thered sandstone fracture surface. By analyzing the morphological characteristics of red sandstonefracture surface, we knew the fracture extension characteristics, grain boundary fracturecharacteristics of red sandstone under different temperatures.The result indicated that hightemperature make the differences among the rupture form of red sandstone crystal boundary, andthen affected its macro mechanical properties。This experiment revealed the microscopicmechanism of red sandstone macroscopic rupture characteristics under different temperaturesfrom the microscopic point of view.（4）Combined with rock statistical strength theory、damage mechanics and mechanicalproperties of red sandstone under high temperature, we got damage evolution model whichcontained temperature factor. Based on experimental results and the concept of thermal damage,we proposed an expression of thermal damage model. Theoretical model correlated well withexperimental results, it accurately described the influence mechanism of temperature on red sandstone mechanical property.