Embankment Dam Design with Dispersive Soil: Solutions and Challenges

The configuration and safety factor of rockfill dams design depend on materials used in construction of the dam. In some regions, the available materials for using as impermeable element of the dam body are dispersive and it is inevitable to consider the dispersivity of the material in the design and construction. Internal erosion through cracks or other openings in the embankment is the most concern of using the dispersive soils. The authors have designed an embankment dam by using dispersive soil in East Africa after finalizing the dispersivity of materials based on the required tests. The foundation of dam and borrow areas consisted of dispersive soil and the effective measures has been considered in the design to safely deal with dispersivity according to recommendation of the design codes. The selected solution was the combination of chimney filter, filter drain, and selective placement of materials in the dam body as the effective solution considering the specification of the project. More precautions in addition to general recommendation have been incorporated into the design criteria due to placing the project in high hazard category. The local instability in the contact zones was the concerns of designers and bilinear parameters has been considered in the stability analysis as the base case. A drainage layer was added into half of the length of filter blanket and the feature of the design was determined according to nonlinear static and dynamic analysis of the dam body. This paper presents the measures and precautions that were taken into account in dealing with dispersive soil in order to ensure the safety of design.