Constructional Deformations in Rockfill Dam

Movements of 26 steel plates buried in the downstream rockfill of Llyn Brianne Dam (90 m) were measured during construction in relation to reference pillars founded on rock away from the dam, by both triangulation and three-dimensional trilateration and the use of three horizontal plate gages, of which the plates formed a part. These movements are compared with those predicted from fill properties derived from large-scale laboratory tests by an analysis using a finite element technique. In general, the movements were greatest at the boundary between the rockfill and the clay core, and decreased towards the toe. Horizontal movement of the downstream slope was greatest at about mid-height where it was 0.68% of dam height and similar to the horizontal movement measured at two other rockfill dams. The movements are analyzed and compared with those of three other rockfill dams and one earthfill dam during failure.