Study On The Migration Of DNAPLs In Stochastic Network Fracture

Now everybody for organic chemical products increased usage,a large number of organic products such as heavy non-aqueous phase liquid(DNAPLs)refining and into the underground environment in use process,because of DNAPLs incompatible with water,by gravity and capillary pressure and viscous force under the action of migration,will eventually remaining in the migration path,this makes DNAPLs pollution source of groundwater environment medium,causing serious pollution of groundwater.At the same time,fracture is one of the three storage Spaces of groundwater.Due to its randomness and heterogeneity,it is more difficult to repair and cure after being polluted by DNAPLs.Therefore,groundwater pollution control and remediation work is the current economic and social sustainable development of the top priority.The migration and distribution of dense non-aqueous phase liquid(DNAPLs)in fractured media are affected by many factors,including physical and chemical properties of DNAPLs,geometric and chemical properties of fractures and leakage conditions.Previous studies were mostly conducted in a single fracture,while the migration of DNAPLs in stochastic network fracture lacks research.In this paper,stochastic network fractures are generated using Monte Carlo method.The coordinates and apertures of fractures are identified and output by pixel scanning.The migration of Perchloroethylene(PCE)in stochastic network fractures was simulated by Petrasim.The spatial variability of crack width,leakage conditions(including leakage rate and leakage location)and the density of DNAPLs on the migration law of DNAPLs are discussed.The numerical simulation results show that spatial variability of fractures affects the migration path and spatial distribution of DNAPLs.With the change of spatial variability of fracture width in network fractures,the downward migration rate of DNAPLs is different,and the centroid position and spatial distribution of saturation of DNAPLs also change significantly.The leakage rate affects the migration range and spatial distribution of DNAPLs.The higher the leakage rate is,the faster the migration rate of DNAPLs will be.The more saturated the accumulated DNAPLs at the bottom of the model,the greater the spatial distribution of DNAPLs will be.The migration path and distribution range of DNAPLs are also different when the leakage location is different in the same network fracture.The spatial variability of fractures in the gravity direction of different leakage locations is different,leading to different migration paths and spatial distribution of DNAPLs,and the time of DNAPLs arriving at the bottom of the model is also different.Different DNAPLs have different densities,migration rates and time to reach the bottom of the model,so the centroid position and spatial distribution of different DNAPLs are also different.The higher the density is,the faster the migration rate is,the faster the time to reach the bottom of the model is,and the change of centroid position and spatial distribution is the least.The research results of this paper are expected to enrich the research on the migration mechanism of DNAPLs in fractured media and provide a model reference for the remediation of DNAPLs pollution in fractured media.