Seepage and flow nets

Seepage and flow nets

1. Theory of seepage

   • Seepage flow refers to the flow of a fluid (water) in permeable soil layers such as sand. The fluid fills the pores in the unsaturated bottom layer and moves into the deeper layers as a result of the effect of gravity.

2. Understand flow nets

   • The flow of water (seepage quantities) through a soil can be represented graphically by a flow net, a form of curvilinear net made up of a set of flow lines intersected by a set of equipotential lines.

3. Draw Flow nets

4. Determine seepage quantities

   • Seepage quantities can be determined from flow nets using Darcy’s law. Flow is assumed to be two -dimensional so a unit width of the cross-section is considered. The total flow rate around a structure will then depend on its overall length.