Study On Mechanical Properties And Fracture Evolution Law Of Prefabricated Fractured Sandstone

Underground projects will face more problems with fractured rock mass control in the future.Therefore,correct understanding of the mechanical properties and fracture evolution process of fractured rock mass contributes to the proposal of stability control technology for underground engineering rock mass,which has important engineering application value.The paper takes prefabricated fractured sandstone as the research object,and uses the RMT-150 B rock mechanics test machine,RLW-2000 rheometer and digital speckle system to study its uniaxial,creep mechanical properties and fracture evolution process.The following conclusions are drawn:(1)The presence of cracks weakens the strength characteristics of the specimen and changes the deformation characteristics of the specimen.The peak strength,elastic modulus and peak axial strain of prefabricated fractured sandstones are reduced compared to intact rock samples.But the secant modulus,peak hoop strain,and Poisson’s ratio change are different.The uniaxial creep strength of prefabricated fractured sandstone has no obvious correlation with the width of rock bridge,and the deformation characteristics remain basically unchanged at low stress levels.Using the Weibull distribution and energy conservation principle,based on the lemaitre hypothesis,the damage constitutive model of prefabricated fractured sandstone is derived and the validity of the model is verified.(2)Overall,the failure mode of prefabricated fractured sandstone is mainly caused by tensile failure,shear failure,and tensile-shear failure.With the increase of the width of the rock bridge,the failure mode of the prefabricated fractured sandstone transitions from the shear failure to the tensile failure after the tensile-shear combination failure.With the increase of the dip angle of the rock bridge,the failure mode of the prefabricated fractured sandstone is gradually changed from tensile-shear failure to shear failure.The fluctuation of each stress-strain curve corresponds to the development and expansion of the crack.(3)The numerical simulation results show that the crack initiation position of the prefabricated fractured sandstone sample is located at the tip of the fracture.The number of crack propagation is mainly concentrated after the peak.The mechanical characteristics and failure mode of prefabricated fractured sandstone specimens are basically the same as those laboratory tests with the width of rock bridge and inclination of rock bridge,which verifies the correctness of the laboratory test.