ABSTRACT
The Grand Ethiopian Renaissance Dam (GERd) Project is located along the Blue Nile River in Ethiopia. This paper is focused on the main design and construction aspects of the composite cut-off system of the Saddle Dam (60 m high and 5 km long, 15 Mm3 of embankment volume), executed all along the central portion of the dam founded on residual soils (about 4 km).
Composite cut-off, constituted by pressure grouting and plastic diaphragm panels, was conceived to address two different requirements: permeability and erosion control.
This paper covers the investigations carried out to assess the erodibility of foundation material and the design elements conceived to counteract the unlikely sequence of events that, if occurring in progression, would have the potential of evolving into a progressive erosion process. Moreover, the criteria adopted to define the extension of diaphragm panels and the continuous refinement process of diaphragm geometry following the construction progress and the acquisition of additional geotechnical information are discussed in details. Finally, the assessment of composite cut-off system is provided based on the data acquired during the implementation of the works.
