Numerical Simulation Study Of Seepage-dissolution In Rock Mass Fractures Based On Lattice Boltzmann Method

Under the infiltration conditions of complex water environment,some soluble mineral components contained in the rock mass will chemically react with the aqueous solution,and the solute migration driven by water pressure will make the chemical weathering more intense,resulting in the derivation of fractured pores on the surface and inside the rock mass,which greatly reduces the physical and mechanical properties of the rock mass,which will bring great hidden dangers to the stability and safety of the construction of water-related engineering;Therefore,based on the lattice Boltzmann method based on lattice Boltzmann method,the seepage dissolution process of rock mass fracture under the influence of different factors is numerically simulated,and the seepage dissolution law of two-dimensional rock mass fracture,Tyson polygon fracture network and three-dimensional anastomosis fracture is analyzed in detail.(1)The rough micromorphology of two-dimensional rock mass fractures was analyzed,and the fracture morphology of rock mass fractures was discussed,which were smooth,trapezoidal,rectangular,parabolic and triangular,as well as the change of fracture morphology,the size of solid dissolution amount and fracture permeability and the change law of fractal dimension during dissolution.This is followed by the law of triangular,parabolic,trapezoidal,rectangular fissures.(2)In the seepage dissolution process of two-dimensional rock mass fractures,the concentration diffusion of low-concentration fluids will also be affected by the rough micromorphology,and the degree of blockade of the five fractures is the strongest rectangular fracture in order from largest to smallest,followed by trapezoidal,parabolic and triangular fractures,and the blocking effect of smooth fractures is minimal,so that the size distribution of fracture center concentration is positively correlated with the retardation,while the speed of dissolution rate is negatively correlated with it.For the dissolution amount of solids,the dissolution amount of the five fractures reached a peak when the dissolution time was 500 s,and the dissolution amount before this peak was consistent with the velocity,and then the dissolution amount continued to decrease,and its size gradually showed the opposite law to the velocity.In the dissolution process of rock mass fractures,the permeability and velocity distribution law are consistent,while the fractal dimension representing the roughness of the five fractures is opposite to the velocity size distribution law,and the fractal dimension of the rough fracture shows a decreasing trend during the dissolution process,while the fractal dimension of the smooth fracture is slowly increasing.During the seepage dissolution of Tyson polygonal fractures,the relative permeability and porosity of fractures were analyzed under different Pe and Da numbers,and the results showed that the relative permeability and porosity increased with the increase.(3)In the seepage process of three-dimensional anastomosis fracture,the pore size of the fracture was statistically found to be normally distributed,and at the same time,under the action of normal stress,the pore diameter and permeability of the rock mass gradually decreased,while the closed displacement,relative contact area and rock mass stiffness gradually increased.(4)In the process of seepage dissolution of anastomosis fractures under different normal stresses,the greater the stress,the more relative contact between the fractures of the upper and lower parts of the rock mass,the greater the degree of diffusion hindrance of the raised rough elements of the rock mass to the concentration,the greater the gradient distribution of the concentration,so that the convective diffusion efficiency of the concentration is low,from the morphology of the anastomosis fracture,with the progress of dissolution,the fracture surface of the rock mass at the entrance of the fracture gradually becomes smooth,and the opening of the fracture also increases.However,due to the blocking effect of the fracture rough element,the internal fracture morphology remains rough.The dissolution amount and fracture permeability of rock mass showed a downward trend with the increase of normal stress,and during the dissolution process,the pore size of the fracture slowly increased,but with the increase of normal stress,the increase of pore size also decreased.Under different dissolution rates,the high dissolution rate makes the amplitude of pore size increase obvious,the dissolution situation is vertical strip,while the low dissolution rate makes the pore size growth of rock mass fractures relatively uniform,the dissolution process occurs slowly,the fracture channel is gradually widened,the dissolution morphology is step-shaped,the size of the permeability increases with the increase of the dissolution rate,and the dissolution time required to achieve the same permeability is significantly shortened.