Water from Small Dams

Homogeneous dam walls can be built of the soil types classified as GC, SC, CL andCH, and if the soil has a clay content of 20% to 30%. (See Chapter 7 for soil analysis).A homogeneous dam wall built of one type of soil. The letters refer to the soiltypes listed above.Zoned dam walls consist of a core of clayey soil whose sides are supported withsandy soil. It is a more stable and economic design than a homogenous dam wallbecause it can be built with steeper slopes, thereby reducing the cost of earth works.A zoned dam wall with a core of clayey soil supported by sandy soil.Diaphram dam walls are used where there are plenty of rocks and/or stones or gravelon a site. These pervious materials are covered on the upstream side with animpervious blanket (diaphragm) of soil with a clay content of 12% to 40%. Theblanket must start below the front toe to prevent seepage under the dam wall.A diaphragm dam wall with a blanket of clay soil covering pervious materials.37