Particle Discrete Element Simulation Study On The Softening Effect Of Heterogeneous Rock By Absorbing Water

This paper is based on the particle discrete element method,using the particle discrete element software PFC2 D to perform uniaxial compression numerical simulation experiments,using the controlled variable method to analyze the sensitivity of the change law of macromechanical parameters and mesomechanical parameters,and establishing considerations based on Weibull distribution Heterogeneous rock water softening numerical model.On this basis,the influence of heterogeneity on rock mechanical properties and water content on rock water softening effect is studied.The main conclusions obtained are as follows:(1)The meso-mechanical parameters that have a greater impact on the uniaxial compressive strength of the rock sample are the parallel bond radius multiplier,the parallel bond normal strength and the parallel bond cohesion.The mesomechanical parameters that have a greater impact on the elastic modulus are the parallel bond effective modulus,the effective modulus and the parallel bond radius multiplier.The friction coefficient has little effect on the failure mode of the rock sample,and the other main mesomechanical parameters have obvious effects on the failure mode of the rock sample;(2)The heterogeneity has a great influence on the macroscopic mechanical properties and damage of the rock sample.When the shape parameter is increased from2 to 10,the uniaxial compressive strength increases from 41.92 MPa to 65.90 MPa,an increase of 57.2%,and the change pattern shows an exponential function relationship;the elastic modulus increases from 14.50 GPa to 14.71 GPa,only an increase of 0.21GPa;damage The variable threshold was reduced from 0.042 to 0.005,a decrease of 88.1%,showing an exponential function change.When the damage variable exceeds its threshold,the damage variable enters the damage destruction stage,and the microcracks enter the rapid development stage.The macroscopic manifestation is that the microcracks quickly converge to form macroscopic cracks and cause the specimen to be destroyed.;(3)Water content has a significant influence on the mechanical properties of rock samples.When the moisture content increases from 0% to 2.82%,the uniaxial compressive strength is reduced from 77.7MPa to 35.7MPa,which is a decrease of54.1%;the elastic modulus is reduced from 15.50 GPa to 10.51 GPa,which is a reduction of 32.2%;parallel bonding radius multiplier Reduced from 1.1 to 0.53,a reduction of51.8%,and the uniaxial compressive strength,elastic modulus and parallel bond radius multiplier and the change law of moisture content all conform to the exponential function relationship;(4)From a mesoscopic point of view,the mechanism of the influence of water content on the water softening effect of rock is analyzed: as the water content increases,the bonding area between particles gradually decreases,and water will lubricate the mesostructure of the rock sample.The mesostructure of the rock sample gradually becomes loose.Due to the dissolution and hydration effect of water on the rock sample,the bond between the particles is destroyed,and the mesostructure of the rock sample is changed,resulting in the gradual cohesion of the rock sample.Under the action of external load,stress concentration is likely to occur in places where the inter-particle bonding area is small and the mesostructure is severely damaged,which makes the rock sample more prone to micro-cracks and secondary fracture surfaces during the loading process.As a result,the bearing capacity of the rock is reduced,the ability to resist deformation is weakened,and the degree of fragmentation when the rock is damaged is obviously increased.With the increase of water content,the failure mode of rock gradually changes from tensile failure to shear failure.