Design of Liquid Collection Layers With Radial Flow

The present paper provides equations for the design of liquid collection layers sloping radially toward a sump located in a corner of the liquid collection layer. It is pointed out that an equation currently used by some design engineers is not correct because it corresponds to the case of confined flow, which is not the type of flow that should take place in a liquid collection layer; this equation leads to grossly underestimated values of the required thickness and hydraulic transmissivity of liquid collection layers. A detailed discussion of the difference between confined and unconfined flow is presented. Design examples are provided.