| The deep rock mass is usually under the action of high temperature and high ground stress.The disturbance of artificial construction will cause the deep rock mass to be in a typical unloading process.Therefore,it is of great theoretical significance for resource safety mining and underground engineering construction safety to study the mechanical properties and deformation characteristics of deep rock under the influence of high ground stress.In this paper,the uniaxial,triaxial loading and unloading tests of red sandstone and shale after high temperature are carried out respectively,and the mechanical behavior,deformation and failure strength characteristics are studied.The specific research contents are as follows:(1)The uniaxial compression tests of red sandstone and shale after high temperature are carried out respectively.The results show that the elastic modulus and peak strength of red sandstone decrease with the increase of rock temperature.When the temperature is 800 ?,the peak strain of red sandstone increases greatly,and its failure forms are axial splitting and local shear failure.However,the compressive strength of shale decreases rapidly with the increase of temperature,and its elastic modulus and peak strain also decrease as a whole.The failure patterns are mostly shear failure,and the higher the temperature is,the more severe the fracture degree is.(2)The triaxial compression test of red sandstone and shale after high temperature shows that: the larger the confining pressure is,the higher the peak strength and peak strain of red sandstone and shale are;in addition,with the increase of the temperature acting on the rock sample,the rapid increase of the peak strain of red sandstone indicates that the high temperature enhances the plasticity of rock,whenT?400?,the peak strength of red sandstone increases slightly,when T?600?,the peak strength of red sandstone decreased rapidly,and the failure patterns are mostly shear failure.However,shale is more sensitive to high temperature,and its peak strength and strain decrease with the increase of temperature,showing brittle failure.The higher the temperature,the greater the degree of fracture and the more complex the failure surface.(3)The results show that the peak strength and peak strain of red sandstone increase with the increase of confining pressure,and the lateral and volume strain confining pressure flexibility is much greater than the axial confining pressure flexibility,which further indicates that the red sandstone is the rock failure caused bydilatancy and crushing expansion in the unloading test,and the higher the rock temperature is The results show that the axial peak strain and the transverse peak strain are increasing,the unloading and expansion characteristics of red sandstone are more obvious,the cohesion and internal friction angle are smaller,the failure pattern is mainly shear failure,and the local area is accompanied by longitudinal splitting failure,that is,shear and axial splitting mixed failure.(4)In the process of rock uniaxial compression test,the acoustic emission test was carried out simultaneously.The results show that when the rock sample loading enters into the plastic yield stage,the acoustic emission information becomes very active and individual peaks appear.When the loading stress reaches the peak,the acoustic emission signal is the strongest and there are many peaks,at this time,the rock sample is cracked.By comparing the cumulative ring count rate of AE at different temperatures,it can be found that the absolute value of slope of red sandstone decreases in the post peak stage after the high temperature action,which shows that the high temperature action makes the red sandstone change from brittle to elastic-plastic.However,the higher the temperature of shale is,the less the acoustic emission information is in the loading process,which indicates that a large number of new fractures have been generated in shale because of the high temperature action,so that the fracture signal is reduced during the loading process.(5)The energy evolution law of red sandstone and shale in uniaxial,triaxial loading and unloading tests after high temperature is studied.The variation law of total energy,elastic strain energy and dissipation energy absorbed by unit rock sample with confining pressure and temperature at the peak stress point and failure point is analyzed.In addition,based on the energy evolution,the failure shape function in partial plane is introduced.The strength criterion of rock under complex stress state is established theoretically,and the spatial failure surface of rock in main stress space is obtained.The criterion can describe the nonlinear characteristics of rock in p-q plane well,and ensure the smooth and convex characteristics in partial plane.This dissertation includes 192 figures,8 tables and cites 90 references. |
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