Experimental Study On Rockburst Tendency Of Fractured Sandstone Under Thermal Stress

Rock burst is a common dynamic disaster in deep underground engineering.Due to the complexity of rock burst in deep underground engineering,the tendency of rock burst needs to be further studied.In particular,the research on rockburst tendency of fractured rock mass under multi field action is still in its infancy.Based on this,the uniaxial compression test and uniaxial loading and unloading test of sandstone under different temperatures are carried out to judge the rockburst tendency of sandstone through the characteristics of stress-strain curve and the criterion of residual elastic energy index;Then,uniaxial compression tests were carried out on the fractured sandstone treated at different temperatures to obtain the stress-strain curve and study the mechanical properties of the fractured sandstone treated at different temperatures;The acoustic emission monitoring system is used to collect and analyze the acoustic emission signals generated in the process of rock failure,and the rockburst tendency of fractured sandstone after different temperature treatment is studied;The results show that sandstone has good rockburst tendency after different temperature treatment;When the fracture angle is certain,with the increase of temperature,the yield characteristics of sandstone tend to weaken,the brittleness,internal loss and stability time first increase and then decrease,the internal friction angle increases and the cohesion decreases.When the temperature is constant,with the increase of fracture dip angle,the yield characteristic of sandstone decreases first and then increases,the brittleness,internal loss and stability time increase first,then decrease and then increase,the internal friction angle decreases and increases first,and the cohesion decreases and then increases first;When the number of fractures is fixed,the yield characteristics,brittleness,internal loss and stability time of sandstone tend to weaken with the increase of temperature;The internal friction angle first increases and then decreases,and the cohesion first decreases and then increases.When the temperature is constant,the yield characteristic of sandstone increases with the increase of the number of fractures;The brittleness decreases,the internal loss and stability time decrease,and the internal friction angle decreases;Cohesion increases;Before the fracture specimen is damaged,the acoustic emission count and acoustic emission instantaneous energy value are at a low level,and the maximum acoustic emission count and acoustic emission instantaneous energy value appear around the peak point.Before the sandstone specimen is damaged,the internal damage is relatively slow,but there is precursory information before the sandstone specimen is damaged,and the specimen is damaged suddenly.The test results can provide a preliminary theoretical basis for the prevention and control of rock burst in fractured sandstone under thermal stress.The main research results of this paper are as follows:(1)Weibull distribution function is introduced.Under the condition that the strength of micro element obeys Hoek Brown criterion,considering the influence of residual strength,introducing damage correction coefficient and considering the factor of damage threshold,the rock damage constitutive model considering the influence of temperature is established in the form of piecewise function for the constitutive model.(2)Through uniaxial compression test,the deformation characteristics,deformation parameters,strength characteristics,crack propagation law and failure characteristics of sandstone treated at different temperatures are known.(3)The rockburst grade of sandstone treated at different temperatures is determined by the residual elastic energy index criterion.(4)Uniaxial compression tests are carried out on sandstone with different fracture dip angles treated with different temperatures,and the relationship between deformation characteristics and temperature and between deformation characteristics and fracture dip angles are analyzed;The relationship between elastic modulus and fracture Inclination after different temperature treatment is analyzed;The relationship between Poisson’s ratio and fracture dip angle after different temperature treatment is analyzed;The relationship between peak strength and fracture dip angle after different temperature treatment is analyzed;The relationship between impact number and fracture Inclination after different temperature treatment is analyzed;The relationship between the instantaneous failure energy of acoustic emission and the crack Inclination after different temperature treatment is analyzed;The relationship between elastic modulus and temperature under different crack inclination is analyzed;The relationship between Poisson’s ratio and temperature under the action of different fracture dip angles is analyzed;The relationship between peak strength and temperature under the action of different fracture dip angles is analyzed;The relationship between impact number and temperature under the action of different fracture dip angles is analyzed;The relationship between acoustic emission instantaneous failure energy and temperature under the action of different crack inclination is analyzed;The failure patterns of specimens treated at different temperatures and the gradual change law of internal failure of specimens are summarized.(5)The relationship between deformation characteristics and temperature and the relationship between deformation characteristics and fracture number are analyzed;The relationship between elastic modulus and the number of cracks after different temperature treatment is analyzed;The relationship between Poisson’s ratio and the number of cracks after different temperature treatment is analyzed;The relationship between the peak strength and the number of cracks after different temperature treatment is analyzed;The relationship between the number of impact and the number of cracks after different temperature treatment is analyzed;The relationship between the instantaneous failure energy of acoustic emission and the number of cracks after different temperature treatment is analyzed;The relationship between elastic modulus and temperature under the action of different number of cracks is analyzed;The relationship between Poisson’s ratio and temperature under the action of different crack numbers is analyzed;The relationship between peak strength and temperature under the action of different crack numbers is analyzed;The relationship between impact number and temperature under the action of different crack number is analyzed;The relationship between acoustic emission instantaneous failure energy and temperature under the action of different crack numbers is analyzed;The failure patterns of specimens treated at different temperatures and the gradual change law of internal failure of specimens are summarized.