Analysis Of Deformation And Failure Characteristics Of Pre-cracked Granite Samples With Triaxial Experiments And Discrete Element Method

Jointed rock masses are commonly encountered in construction of some engineering,such as water resources and hydropower engineering,railway engineering,geothermal exploitation,and oil and gas engineering,etc.The exist of joints and cracks in the rock may affect the mechanical properties of rock,and the change of macro mechanics parameters is closely related to cracks formation,propagation,and coalescence.In this paper,in order to research on effect of type of pre-existing cracks and confining pressure on macro mechanics parameters and failure modes,A series of trixial experiments on five kinds of pre-cracked granite samples was conducted under confining pressure of 0,5,and 10 MPa,respectively.Correspondingly,all the experiments were numerically simulated by particle flow code PFC2 D.The simulated results are compared with the experimental results.On the basis of reliability of numerical model,the spatial distribution of the internal mesoscomic parameters of rock samples in the loading progress were obtain,which provided good conditions for research on mesoscomic mechanism of macroscopic mechanical characteristics of rock.The main result of this research are as follow:In the condition of same confining pressure,the strength and elasticity modulus of the rock sample decrease with the increase in number of pre-existing cracks;in the condition of same type of pre-existing cracks,the strength,elasticity modulus and axial strain and radial strain corresponding to strength increase with the increase in confining pressure.The stress of intact rock granite sample drops rapidly with the axial strain once it reaches its peak,resulting the stress-strain curves showing as a“V” shape;while the stress of pre-cracked samples decrease slowly with the axial strain.The failure mode of an intact sample under uniaxial compression is splitting failure.For pre-cracked samples under uniaxial compression,the cracks forms first at the tips of the pre-existing cracks,and they then propagate in the axial direction and finally form a connected splitting failure.For pre-cracked samples under triaxialcompression,the failure mode are mainly tensile-shearing failure.In addition,the crack propagation rules of the samples under uniaxial and triaxial compression were analyzed with the particle flow code PFC2 D,And explain the confining pressure from the mesoscopic mechanism and fracture effect on macroscopic mechanical parameters.The experimental reach and numerical simulation of macro and micro combined with each other verification.