Study And Numerical Simulation Of Preferential Flow In Fissure-pore Dual Permeable Medium

In the development of groundwater engineering,people usually analyze the porefracture distribution in the rock and soil mass,so as to study the law of seepage and solute transport in the fissure-pore medium.The microscopic mechanism of soil seepage is pore flow,and the phenomenon of " preferential flow" caused by uneven pore velocity is very common in the seepage process.This paper designs and constructs a new preferential flow physical model for fissure-pore dual permeable medium.An innovative fissure simulation process is adopted to realize the real-time visualization of the whole process of preferential flow simulation.Based on the experimental model of real-time and visualization,dyeing tracer test under different particle size of matrix domain,the advantages of real-time continuous monitoring flow occurs each section point velocity,and quantitative analysis of the fracture-pore double penetration medium under different particle size of matrix domain flow motion,the advantages of the system for different size of matrix under the domain of impact fracture-preferential flow numerical simulation and flow mechanism and distribution law of research.The main conclusions are as follows:(1)In the three matrix domains with different particle sizes,the peak pore flow velocity of each cross-section occurred at the cross cracks,and a small part of the water flow at the cross cracks flowed laterally along the cracks.It shows that the pore area formed by the coarse-coarse grain framework at the cross fissure is smoother than the pore area formed by the coarse-fine grain framework.(2)The smaller the particle size in the matrix domain,the more concentrated the seepage path flow along the direction of large pores,and the faster the flow velocity,the more obvious the preferential flow phenomenon.It indicates that when the rainfall intensity is greater than the infiltration capacity of the matrix domain,but less than or equal to the total infiltration capacity of the soil,the infiltration flow is divided into two parts.The water flow exceeding the infiltration capacity of the matrix domain conducts through macropores,forming macropreferential flow.(3)The Pearson correlation coefficients between the measured flow velocity data and the numerical simulation flow velocity data are all between 0.8-1,which is a very strong correlation,indicating that it is feasible to use Geo-studio simulation software to conduct numerical simulation of the fracture-pore double permeability test.(4)Statistical method was used to calculate the pore velocity of each section in matrix domain with different particle sizes.Based on the Gauss Amp distribution function,Lorentz distribution function and lontz distribution function,the nonlinear curve fitting of the pore velocity distribution frequency was conducted,and the fitting result of Lorentz distribution function was found to be more accurate,and it was believed that the pore velocity in fence-pore double-permeable medium followed the Kosy-Lorentz distribution.(5)The pore velocity in the matrix domains with three different particle sizes all showed a large difference in frequency distribution between the two groups to the right of the peak position.After research and analysis,it was determined that the velocity at this position belonged to the velocity generated during the exchange between the two domains.