The Movement of Water through Soil

This chapter investigates the flow of water through interconnected pores between soil particles in both one and two dimensions. Often, the flow of ground water through a confined or unconfined porous material can be represented as a uniform flow in a plane. The term seepage flow is used to describe the movement of water through or under soil structures to wells, drains and reservoirs. Generally, the Reynolds number defined in fluid mechanics is less than 1, and therefore the flow is laminar and Darcy’s law is valid. Any departure from laminar flow is not serious as long as the Reynolds number is below 10, the upper limit for the validity of Darcy’s law. A simplified theoretical and numerical approach is developed and applied to practical examples to obtain flow nets that describe the seepage flow. This is followed by descriptions of test methods (laboratory and in-situ) used to obtain the coefficient of permeability (or hydraulic conductivity) that controls the velocity and the volume of water flowing per unit of time.