Fracture Experiments And Numerical Simulation Of Cracked Body In Rock-like Materials Affected By Loading Rate

In order to explore the influence of loading rate on the strength,deformation and energy evolution of fractured rock mass,and to analyze the fracture response and energy evolution mechanism of fractured rock mass under the influence of loading rate and dip angle,the rock specimens with different dip angles were prepared in laboratory by embedded aluminium alloy sheet method.Uniaxial compression test at four-stage loading rate of 0.1k N/s,0.2k N/s,0.5k N/s,1.0 k N/s were carried out based on RMT-150 B.In order to make up for the deficiency of laboratory test technology in reflecting the micro-morphology of fracture body,.which based on the PFC2 D numerical calculation platform,the numerical analysis model of fracture body was constructed based on the flat joint contact element,and the boundary conditions were set up,which were the same as the indoor test environment.The complete deformation and failure characteristic data of specimen were compared and the numerical values were calibrated.Meso-mechanical parameters of the model.The main results of this study are as follows:(1)Under static loading conditions,the peak strength of rock-likespecimens is negatively correlated with the strain and loading rate.At the same crack inclination,the peak strength of rock-like specimens increases nonlinearly with the increase of loading rate,but the increasing rate decreases gradually.(2)At the same loading rate,the peak strength of the fractured rock specimen decreases first and then increases with the increase of the inclination angle of the fracture.The peak strength of the fractured rock specimen with 15 degrees dip angle is the smallest.When the inclination angle is 75 degrees and90 degrees,the peak strength of the fractured rock specimen is close to the strength of the complete specimen,indicating that the damage degradation of the fractured rock specimen with large dip angle is weak,especially the 90 degrees dip fracture body.The influence of loading rate and crack inclination on the peak strength of the specimen is almost the same as that of the complete specimen.(3)The elastic modulus of the fracture body is affected by both the crack dip angle and the loading rate,and increases approximately linearly with the increase of the crack dip angle.It increases nonlinearly with the increase of the loading rate and tends to a constant.(4)The stress response law of the crack tip during the numerical simulation test shows that before the stress-strain relationship curve drops at the same loading rate,the stress at the crack tip of 15 degree dip angle is greater than that at other dip angles;the normal stress and tangential stress atthe crack tip vary with the increase of the crack dip angle: the normal stress decreases and the tangential stress increases with the increase of the crack dip angle.(5)The elastic strain energy of the fracture body still accumulates after peak value,but the ability to accumulate elastic strain energy decreases with the increase of loading rate(6)The transformation rate of dissipated strain energy of the fracture body is at a low level before the peak value,and increases sharply with the penetration of macro-fracture surface after the peak value;the damage degree of the fracture body varies with the loading rate,which the corresponding damage factor and the loading rate decrease with the increase of loading rate.The law of damage factor variation affected by loading rate is consistent with the law of energy evolution,which indicates that there is an intrinsic relationship between the energy evolution process and failure law.