Gradients of seepage velocity model for contaminant transport prediction

Abstract Models are commonly used to predict the contaminant transport. For example, hydraulic conductivity, porosity and gradient are parameters for seepage velocity model. The variation of each parameter needs to be considered for different grain size in order to determine accurate seepage velocity model. An experimental set up was used to determine hydraulic conductivity vis-a-vis permeability for sands of different porosities at different gradients, ranging from 1.15 to 15.00. The permeablities at gradient 1.15 are 0.466 × 10−11, 1.054 × 10−11, 1.175 × 10−11, 1.690 × 10−11 and 3.293 × 10−11 m2 for sands of porosities 0.250, 0.333, 0.364, 0.400 and 0.420 respectively, while the decline permeabilities obtained at higher gradient 15.0 are 0.334 × 10−11, 0.942 × 10−11, 1.023 × 10−11, 1.550 × 10−11 and 2.684 × 10−11 m2 for sands of porosities 0.250, 0.333, 0.364, 0.400 and 0.420 respectively. It was observed that pre-field test or models for fine grained sand and coarse grained sand cannot be subjected to the same gradients for high degree of prediction. Thus, in the model or pre-field test experiment, lower gradients (below 1.88) are more appropriate for coarse grained sand, while higher gradients (above 2.50) should be used for fine grained sand. This recommendation will be appropriate for the accurate prediction of contaminant transport seepage velocity in each case.