THEORETICAL MINIMUM COST COMBINATION OF DEPTH AND SPACING FOR SUBSURFACE DRAINS UNDER RADIAL FLOW CONDITIONS

Subsurface drainage installation cost should be minimized by proper design and the appropriate combination of depth and spacing of drains. An equation has been developed to determine the optimum combination of drain depth and spacing for conditions in which significant radial flow into the drains is present. Material to excavation cost ratio has been included in the proposed equation. Furthermore, a semigraphical solution to the equation has been given. The application of the proposed equation for different conditions is discussed.