Study On Solute Transport And Natural Potential Response Characteristics Of Single Fracture

Single fracture is the most basic unit structure of complex fracture system.It is a common phenomenon that natural fracture is filled with media material.Studying the law of solute transport in fissured fissures plays an important role in understanding the migration and diffusion of pollutants in underground media.On the basis of summarizing the research results of relevant scholars both at home and abroad,this paper comprehensively uses the methods of theoretical analysis and indoor simulation to construct a physical model of filling a single fracture with a smooth plexiglass plate filled with gravel media,Filled fissures and solute transport simulations,the breakthrough curve of solute transport in fractures was drawn,and the convection dispersion equation(ADE)was used to fit the model.The natural potential monitoring method based on geophysical methods Real-time monitoring of solute transport in single-fill fissures.Through the analysis of the test results to explore the following conclusions:(1)Under the condition of low flow velocity,the filling single fissure and the single width flow conform to the Darcy formula,the Forchheimer formula and the Izbas formula.With the increase of flow velocity,the relationship between hydraulic gradient and single width flow begins to show a nonlinear state.(2)When the sand sample composition is the same,the greater the hydraulic gradient,the higher the breakthrough curve first peaks.The smaller the opening,the shorter the duration of tailing;at the same hydraulic gradient,the smaller the particle size of the filled sand,the smaller the porosity of the fracture.The smaller the degree,the smaller the flow velocity of the water,and the longer the breakthrough curve reaches the peak value,the larger the opening of the curve.(3)It can be seen from the fitting that the penetration curves of the solute transport in both the vertical and horizontal filling single fractures can be simulated by the water dynamic dispersion equation(ADE),and the fitting effect is good.(4)When the solution reaches each electrode,the measured spontaneous potential value of the electrode mutates.The location,migration speed,and concentration of groundwater contaminant transport can be obtained based on the time-dependent curve of natural potential.The speed of contaminant migration was calculated based on the time point at which each measurement electrode's natural potential jumped.Information on the contaminant concentration and diffusion time can be determined by the peak value and opening direction of the response curve of the natural potential duration.