Investigation On The Regularity Of Contaminant Migration Through Fractured Medium

With the continuous development of expansion of human activities and industrial production, the deterioration of groundwater resources in fractured medium is increasing, which accelerates the scholars on the study of groundwater resources in the fractured media pace. In recent years, resources on the pollution of groundwater have been unfurled at home and abroad. However, these researches mainly concentrated in the porous media and less research in the fractured medium. So research needs to be further improved in fractured media. In order to understand the migration characteristics of pollutants in fractured medium, the mathematical model is established in single fracture. Based on the relevant research, the main work includes the following aspects:1. The mathematical model has been established, which does not considering the biodegradation. Based on Laplace Transform method, the analytical solution has been obtained. Rely on the presented solution, the effect of the relevant parameters of contaminant transport are investigated. The results show that the hydrodynamic dispersion can significantly affect the migration in fracture-matrix system. The hydrodynamic dispersion effect plays an important role in the migration of contaminant.2. The contaminant transport model in a single fracture has been established,which boundary conditions with the linear attenuation of the contaminant transport.The semi analytical method is used to solve the governing equations. The time, the coefficient of the horizontally hydrodynamic dispersion, the coefficient of the vertically hydrodynamic dispersion, retardation coefficient and the biodegradation effect on the migration of contaminant are analyzed. The results indicate that the porosity has little influence on contaminant migration in matrix.The diffusion parameters have effect on the transport of contaminants in fracture medium. The concentration of contaminant in matrix can be greatly reduced when the biodegradation effect is considered. And with the increase of biodegradation coefficient, the influenced depth decreases.3. Based on the theories of contaminant transport in fractured medium, this paper uses the sofeware COMSOL Multiphysics to establish the migration model of parallel fractured medium and irregular fractured medium. Then it simulates the velocity and pressure of the contaminant in fractured medium. Besides, it also analyses the impact of the initial pressure and simulation time. It is found that the initial pressure owes a great inflence on the concentration of contaminant. It is also shown that COMSOL Multiphysics provides a possibility to solve the complex contaminant transport problem.