The Shape Of Lens Formed Of LNAPL In Vadose Zone And The Influence Of The Fluctuation Of The Water Table

After leakage into underground environment,light non-aqueous phase liquid(LNAPL)vertical migration in the vadose zone first.When LNAPL arrive at capillary zone above the underground water,it will form a saturated lens.It is of great guiding significance to predict the lens thickness formed by LNAPL seepaging in the vadose zone for removal and restoration of contaminated aquifer LNAPL.Groundwater level changes with the change of seasons,while the lens on the floating in the water changes,thus in the prediction of leakage when LNAPL lens should be as the change of water level fluctuation situation into account.This article through the vertical force equilibrium analysis of the lens at various points after LNAPL into the vadose zone,come up with a two with LNAPL and water directly into the pressure to predict LNAPL in balance the formation of the formula of the thickness of the lens.And by considering the hysteresis of the soil water characteristic curve,with a simple indoor experiment to obtain the water as the wetting phase,diesel as a non wetting phase,in medium sand and coarse sand moisture content and matrix suction.And then fit the curve with Brooks-Corey model(BC model),Van Genuchten model(VG model)and Fredlund-Xing(FX)model,respectively.Then we conducted two groups of simulated experiment to simulating the diesel leaked into the vadose zone,measured the thickness of the lens above the water table when it become balanced.Finally we conducted several groups experiment of the fluctuation of water table and then took same samples in diffirent point to measure the moisture content and oil content by the methed of GB260-77.Then contrast the change of the lens by the fluctuation of water table.This paper draws the following conclusion:(1)Using the entry pressure of drainage curve and imbibition curve to predict the thickness of the lens in vadose zone is feasible.And VG model is more accurate when solve the entry pressure.(2)When using VG model to predict the thickness of the lens,the predicted values and are small compared to the actual value.The cause of the error could be measured in sand core funnel water and diesel completely wet moisture absorption process,result in the difference between the two into the pressure value and full of moisture moisture absorption curve into the small pressure difference.(3)In the final formation of the lens,the oil saturation with diesel oil migration front is more and more big,the gas and water saturation with diesel oil migration front smaller and smaller.Oil saturation distribution in the lens from middle to both sides to reduce gradually,as the migration front is higher and higher.(4)In a constant water level,water level decline in both cases,preferential for diesel oil in medium water;Under the condition of the water level rise,diesel preferential for the gas in the medium.