THEORETICAL EVALUATION OF BI-LEVEL DRAIN INSTALLATION UNDER STEADY STATE AND RADIAL FLOW CONDITIONS*

Using Dupuit-Forshheimer assumption, an equation was developed to determine the drain spacing at two alternatively different depths (bi-level drains) under steady state flow condition and significant radial flow into the drains. The installation cost of bi-level drains was compared with the uniform drain depth system and has a higher cost than uniform depth drains. The conditions under which bi-level drains might be used were discussed.