The Role of Real-Time Monitoring in Controlling the Installation and Assessing the Performance of a Plastic Concrete Cut-Off

The construction of a plastic concrete cut-off through the core of a newly completed embankment dam is a comparatively rare practice. This paper discusses the design, procurement, construction and performance of the cut off wall and the role of real-time monitoring in securing success of the works. Site conditions required an embankment type dam and ground investigation identified extensive granular alluvial deposits in the valley floor overlying bedrock of mudstone and sandstone. To overcome anticipated shortfall in suitable core fill and to cut through the alluvial soils it was proposed to install a plastic concrete cut off from the dam crest down in to the bedrock. Construction had to overcome variable ground conditions including high pore pressures in the core fill, obstructions in the alluvial soils, coarse granular bands and a relic slip in the bedrock. During construction panel alignment was checked using real-time readout in X and Y planes from logger in the hydraulic grab. Real-time monitoring of pore pressures in the fill, alluvial soils and bedrock was obtained from data loggers connected to vibrating wire piezometers. Upon completion the performance of the wall was monitored as the reservoir impounded by comparing pore pressure readings upstream and downstream of the cut-off.