Aspects off One-Dimensional Filtration

Abstract

In many circumstances, filtration of two-phase (solid-liquid) systems may be described by theory based on Darcy's law and an appropriate continuity equation. In following this approach it is important to recognize that, since both phases are generally in motion relative to an observer, Darcy's law describes the flow of the liquid relative to the solid particles in response to a space gradient of potential (head). It also emerges that analysis is often simplified by recasting the flow equations in a coordinate system based on the distribution of the solid component of the system. The theory requires that relations between the water content and (a) the water potential and (b) the permeability are well defined. Neither functional permits a priori prediction, although various formulas have been proposed in particular circumstances. This paper describes simply and directly the formulation of an appropriate material coordinate. It also provides experimental information relating to important aspects of filtration and the permeability of bentonite slurries subject to constant pressure filtration. It is shown that the one theory describes both filtration and expression, so the distinction between them is artificial.