A study of dense nonaqueous phase liquid infiltration in saturated porous media: Centrifuge simulations and similitude analysis.

摘要

The problem of dense nonaqueous phase liquid (DNAPL) migration in the subsurface was studied with the aid of similitude analysis, analytical solutions, and physical simulations. The scaling laws of two-phase transport were modified to better describe DNAPL migration under constant and falling head conditions. A semi-analytical solution was developed which gives the velocity and location of the DNAPL front and a criterion that describes the mobility condition of the DNAPL front. Several column experiments conducted under 1-g and using different soils and three DNAPLs spanning a wide range of DNAPL properties agreed reasonably well with the model predictions and verified the modified scaling laws.;Two-dimensional simulations of DNAPL infiltration in saturated porous media were performed in the geotechnical centrifuge to: (a) assess current conceptual models, (b) study the mobility trends of DNAPLs in different soil models, and (c) provide data for numerical code validation. Contrary to current conceptual models, the centrifuge simulations showed that low density DNAPLs may reach a halt without encountering a capillary barrier, at DNAPL saturations much higher than residual. In homogeneous soil models, DNAPLs with low density and high viscosity penetrated approximately equally in both dimensions. On the other hand, DNAPLs with high density and low viscosity showed increased mobility in the vertical direction with little lateral spreading. In layered soil models, DNAPL movement was dominated by lateral spreading in the coarse layers. In compacted clays, DNAPL migration occurred primarily in the macroscopic features of the clay such as cracks and interclod voids.