Deep Jet-Grouted Cut-Offs in Riverine Alluvia for Ertan Cofferdams

Constructing the 245-m-high, double curvature concrete arch Ertan Dam required two high cofferdams (the upstream one exceeding 60 m) and the removal of 40 m of alluvium from the riverbed. Full penetration and partial penetration cut-offs were created at Ertan with jet-grouting techniques. Dewatering between the cofferdams and behind the cut-offs was successful and was maintained for more than 2 years against 40–70 m of water heads. This paper describes in detail the design rationale and main features, as well as the construction methods of both cut-offs. The treatment by conventional grouting of the rock below the jet-grouted wall is also outlined.