Numerical Simulation of the Solute Migration Regulated by Vertical Cutoff Wall based on FEFLOW

Abstract

Cutoff wall has been widely used in desalination of coastal aquifers in many coastal regions and remediation of industrial waste water pollution. In recent years, the excessive exploitation of resources in the coastal brine distribution area leads to the salinization of deep soil. At the same time, the mine water pollution caused by improper discharge of industrial waste water into the abandoned mining area is a new form of pollution in Shandong, China. However, due to the complex geological conditions of abandoned mining areas, loose collapse of overlying strata in roadway and gob layer, it is difficult to prevent and control groundwater pollution in deep gob layer. It is a major difficulty in practical engineering to evaluate the cutoff interception performance of vertical cutoff wall on the pollution of gob layer in such mining areas and optimize cutoff interception measures. In this paper, a typical polluted abandoned mining area in Shandong, China is taken as an example, and COD is used as the main simulation factor for numerical simulation. The numerical simulation results show that in the process of groundwater pollution control, the cutoff wall with appropriate thickness and hydraulic conductivity can effectively block the diffusion of solute. The horizontal transport of solute can be significantly weakened when the thickness of the cutoff wall is 90 cm and the hydraulic conductivity is 1.0×10-4 m/d. Compared with increasing the thickness, reducing the hydraulic conductivity of the cutoff wall is more effective in controlling the migration of solute in the site. When the hydraulic conductivity is reduced by an order of magnitude, the diffusion range of solute is reduced by 19.74% compared to before. Therefore, priority should be given to reducing the hydraulic conductivity of the cutoff wall in order to optimize its influence on pollutant migration.