Microscopic Numerical Simulation Of Deformation And Failure Behavior Of Marble Under True Triaxial Stress

Carrying out the study of rock mechanical properties under true triaxial conditions is one of the hot issues in rock mechanics research at present,which is of great significance to promote the development of deep nonlinear rock mechanics,and at the same time provide correct theoretical guidance for engineering practice.In view of this,on the basis of previous research,this paper intends to use the PFC^3D software of particle flow and the diversion tunnel of Jinping Hydropower Station as the research background to conduct a mesoscopic numerical simulation study on the surrounding rock to study marble in the true triaxial state.The mechanical characteristics,fissure development and deformation and rupture forms provide assistance for engineering construction.The main research results are:?1?Through the study and analysis of the sensitivity of each meso parameter of the parallel bonding model in PFC^3D,the effect of each meso parameter on the macroscopic mechanical parameters of the rock is specifically as follows:The parallel bonding model mainly affects the elastic modulus and elastic modulus of the macro specimen The quantity and the effective modulus of parallel bonding are roughly linearly proportional;the Poisson's ratio of the sample depends on the particle stiffness ratio or the parallel bonding stiffness ratio,and also shows an approximately linear relationship,while increasing the effective modulus of parallel bonding will reduce the macroscopic test.Sample Poisson's ratio;normal bond strength and tangential bond strength affect the peak strength of the sample.At the same time,the greater the normal bond strength,the greater the number of shear failures and the less tensile failure,while the tangential bond strength has the opposite The influence of friction coefficient and friction angle on the peak strength has a small increase.Based on the marble numerical model established by previous laboratory tests,the numerical simulation results are consistent with the laboratory test results under true triaxial conditions;?2?The PFC^3D software was used to conduct numerical simulation and compression test research on marble samples under true triaxial conditions,and the mechanical parameter characteristics,unit displacement field and failure mechanism of the marble model were analyzed from a meso angle.Under the true triaxial condition,when the minimum principal stress is a fixed value,the characteristic strength and peak strain of the rock change with the increase of the intermediate principal stress,which shows a quadratic function relationship;the intermediate principal stress starts from the elastic modulus of the rock.To a certain degree of improvement,the elastic modulus has a logarithmic function relationship with the intermediate principal stress.Rock macro-fracture angle increases linearly with the intermediate principal stress.At the same time,the larger the difference between the intermediate principal stress and the minimum principal stress,the more obvious the brittleness characteristics of rock failure morphology;?3?During the cyclic loading and unloading process of the rock sample model under true triaxial conditions,the stress-strain curve will have hysteresis loops in the three principal strain directions,showing a development trend from dense to sparse and gradually increasing in area.The damage evolution process of rocks is revealed by defining damage variables and equivalent irreversible strains,in which the damage variables in the direction of maximum and minimum principal stress and the equivalent irreversible strain present a linear increasing relationship,and the damage variables in the direction of intermediate principal stress appear with the equivalent irreversible strain Exponentially increasing trend;?4?Keep the first stress invariant at a fixed value during loading.When the Lode angle changes from 30°to-30°,the maximum principal stress and minimum principal stress during rock failure gradually decrease,and the intermediate principal stress Increase.The changes of the three principal stresses show an approximately linear development trend,and the effect of the intermediate principal stress effect on the peak strength is less than the minimum principal stress effect.At the same time,when the Lode angle changes from 30°to-30°,the failure form of the rock sample changes from plastic failure to brittle failure,and the angle of the failure surface shows a trend of approximately linear increase.The paper has 51 figures,28 tables,and 85references.