Hydraulic gradient size distribution

Saturation (v) is the volume fraction of the total void volume occupied by a specific fluid at a point. Saturation values can vary from zero to 1 with the saturation of all fluids equal to 1. Residual saturation (Sr) is the saturation at which the NAPL becomes discontinuous and immobile due to capillary forces. Residual saturation is dependent upon many factors, including pore size distribution, wettability, fluid viscosity and density ratios, interfacial surface tension, gravity and buoyancy forces, and hydraulic gradients. 

For soil systems contaminated with Na+, kinematic viscosity is not significantly affected, thus the components controlling water flow velocity are the hydraulic gradient (A< >/AX) and soil permeability (k). The latter component (k) is influenced by clay dispersion, migration, and clay swelling. These processes may cause considerable alteration to such soil matrix characteristics as porosity, pore-size distribution, tortuosity, and void shape. 

It is assumed that the aquifer is confined and hydraulically homogeneous (average hydraulic transmissivity T= 10 m /s, gradient of the natural uniform flow field /= 0.2 %) and composed of Neckar river alluvial (NRA). The lithological composition and grain size distribution of NRA (Tab. 7.1), as determined by Riigner et al. (1997), is... 

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