Failure And Mechanical Properties Of Rock-like Material Containing Stochastic Joints Under Variable Uniaxial Loading Conditions

Engineering rock mass has random distribution of joints,cracks and other defects,and its load is also complex and changeable,research on the mechanical properties of jointed rock and failure process under variable load conditions,is of great significance for the stability analysis and control of jointed rock mass.In this paper,uniaxial compression tests with different loading rates and cycles of loading and unloading were carried out on random jointed rock-like specimens.With the aid of acoustic emission detection equipment,full-field strain measurement and analysis system and PFC2 D numerical simulation software,The influences of joint volume coefficient,loading rate and cyclic loading and unloading times on uniaxial compressive mechanical response,acoustic emission characteristics,deformation failure and crack growth of random jointed rock-like specimens were investigated.The results show that:(1)The ultrasonic wave velocity of random jointed rock-like specimens decreases with the increase of joint volume coefficient.Under uniaxial compression,the joint volume coefficient is negatively correlated with uniaxial compressive strength and elastic modulus,but positively correlated with peak strain.The larger the joint volume coefficient is,the fewer AE events occur in the failure process of rock-like specimens,and the fewer cracks occur after failure.The specimens show a splitting failure mode.(2)With the increase of loading rate,uniaxial compressive strength,elastic modulus and peak strain of random jointed rock-like specimens also increase in different amplitude.The higher the loading rate is,the fewer AE events occur in the failure process of the specimen,the faster the crack development speed,and the lower the crack propagation and penetration degree.When the loading rate is low,the energy accumulated inside the specimen is released relatively fully,and the crack is more likely to initiate and expand.However,at the high loading rate,the energy accumulated inside the specimen cannot be fully dissipated,so the crack cannot expand well.(3)Random jointed rock-like specimens show "memory characteristics" in the process of cyclic loading under uniaxial compression,and the uniaxial compressive strength has a linear positive correlation with the number of cycles.In the initial stage of uniaxial compression and the first cyclic loading and unloading process,the acoustic emission ringing counts are more,and the cumulative energy value increases at a faster rate.However,with the increase of the number of cycles,the ringing counts decrease significantly,and the cumulative energy does not increase significantly.In the process of cyclic loading and unloading,the dissipated energy increases first and then decreases as the number of cycles increases.