Research On Temperature Effect Of The Mechanical Properties Of Sandstone Under Thermo-Mechanical Coupling Effect And Rockburst Criterion Study

Deep buried,long and large scale tunnel engineering under complicated geological conditions always encounter problems like high temperature and high geo-stress.High temperature and other disasters are also the frontier issues in the field of engineering geology,rock mechanics and mining engineering.Based on uniaxial compression test and triaxial compression test under high temperature,a lot of experiments were carried out in this paper focusing on the research of temperature effect of sandstone under high temperature to study the mechanical properties of rock and the mechanism of temperature with the acoustic emission to be the main monitoring means.Firstly,the mechanical properties of sandstone under thermo-mechanical coupling effect was studied and the mechanism of temperature was deeply discussed.Secondly,the response characteristics of AE parameters of sandstone under the thermal-mechanical coupling effect was analyzed from the point of acoustic emission.In the end,the rockburst criterion considering the influence of temperature was put forward on the basis of the above research.Through the work above,the following research results were obtained:(1)The uniaxial compression test under high temperature of sandstone in the Bamiao tunnel was carried out.With the increase of temperature,the discreteness of stress and strain curves of sandstone specimens gradually decrease,and the ductility of the sandstone specimen gradually appeared.The uniaxial compressive strength and peak strain of sandstone increase with the rise of temperature,and the peak strain then edge down slightly.The elastic modulus and deformation modulus showed a trend of first increasing and then increasing with temperature.Poisson's ratio showed a trend of first decreasing and then increasing.Overall,with the increase of temperature,the failure mode of samples change from tension failure to tensile-shear failure failure.(2)The peak strength and strain,average modulus and Poisson's ratio of sandstone increase with the rise of temperature based on the triaxial compression test.The failure modes of specimens changed from tension failure to shear failure with the increase of confining pressure and changed from shear failure to tensile-shear failure with the rise of temperature.When the temperature is low(20? and 60?)the change trend and the line shape is more consistent,the same goes for the other three(90?,120? and 150?),while the curves of lower temperature and higher temperature change trend and line shape is obviously different..(3)The peak value of ringing counts and energy of sandstone increases with increases of strength based on the uniaxial.The active degree of acoustic emission decreases before the peak of stress and enhanced after the peak of stress.With the increase of temperature,The "quiet period" of the acoustic emission ringing counts and total energy become longer,the elastic properties of rock has been enhanced.(4)The peak counts and AE energy of sandstone decreases with the increase of temperature according to the triaxial test under high temperature.With the increase of temperature,the acoustic emission ringing counts and total energy of the whole duration reduced,the peak of both the acoustic emission ringing counts and total energy of AE appears shorter.With the temperature rises,the micro fracture increases,acoustic emission activity is more active.Under different confining pressure,acoustic emission ringing counts and total energy was changed irregularly with the increase of temperature.(5)The different factors influencing the rock burst were classified as one factor(Ft)which is sensitive to temperature and the other which is not.A rockburst tendency index was put forward based on temperature sensitivity and RVI.The mathematical expression of temperature sensitivity factor Ft was put forward based on Stress control factor Fs.It is also pointed out that to predict the rock burst damage under thermal-mechanical coupling effect also need a large number of case analysis with the fitting relationship between the depth of rock burst damage and the value of TRVI.