Arminou Dam, Cyprus, and construction joints in diaphragm cut-off walls

This paper is in two parts. The first part describes the foundation seepage cut-off to a new 42 m high gravel fill dam with central clay core. A single 0·8 m wide plastic concrete diaphragm wall, together with adjacent bentonite cement alluvial grouting, provides a seepage cut-off through the 15 m depth of underlying granular alluvium. The discovery of bentonite infill in construction joints in trial panels for the diaphragm wall led to the introduction of alluvial grouting, to inhibit erosion of this bentonite infill into coarse zones in the alluvium. The second part of the paper discusses the main factors governing the effectiveness of diaphragm walls as seepage cut-offs and related dam safety issues, including construction joints, hydraulic gradients and hydraulic fracture. There are a number of issues relating to the use of diaphragm walls as seepage cut-offs that are not well understood, which should be considered in design, construction and monitoring of such walls and where further research is needed.