Diaphragm Wall Behaviour Under Thick Alluvium Layer Conditions

Diaphragm walls play an important role in the majority of structures built on non-rocky ground. In the particular case of dams, one way of dealing with tightness issues in alluvial valleys lies in the installation of a diaphragm wall, making it possible to connect the watertight components of the main structure to the rock foundation. This article analyses the specific case of a Concrete Face Rockfill Dam, resting on approximately 35 m of alluvium. To overcome tightness issues caused by alluvium at the bottom of the valley, a plastic concrete diaphragm wall was built. The objective of this paper is to analyse the behaviour of this diaphragm wall during all phases of the dam’s construction. It turns out that the plastic concrete wall undergoes a double behaviour: on the one hand, it deforms laterally with the alluvium which settles and widens on both sides of the axis of the Dam; and on the other hand, it withstands these displacements in term of stresses, limiting the large deformations. It emerges from this study that the plastic property of the concrete used in the diaphragm wall plays a major role in the consistency of the entire structure.