ABSTRACT
In the 20 years since the first all-RCC dam was constructed many “innovations” have been developed, some successful and others not. With RCC dams now reaching 200 m in height new ideas and procedures for improving quality and reducing construction time and cost are having more impact. Five of many recent innovations developed over the last 5 to 6 years or so are described in this paper. The author selects them since they have considerable significance for the future of RCC dam design and construction and because of his personal experience with each of them. The Sloped Layer Method (SLM) enables joints between RCC layers to be made within the initial set time of the lower layer, thereby achieving monolithic RCC, saving the cost of joint treatment and increasing RCC placing rates. Grout enriched RCC (GE-RCC) is a simple technique to modify in-place loose RCC to have the properties and workability of conventional concrete; consolidated by internal vibration it can provide an excellent off-form concrete finish for facing of spillway steps, impervious upstream facing, embedment of waterstops etc., reducing costs and not holding up RCC placing as experienced with conventional concrete. The simple change from the “traditionally adopted” upstream crossfall, provided to RCC lift surfaces to assist with drainage of lift surface washwater and waste and rainfall runoff, to a downstream crossfall, achieves protection to the critical upstream zone of RCC dams, enhancing the probability of achieving impermeable, bonded lift joints where most needed, yet detracting little from overall sliding resistance of the lift joints. Cooling of RCC only in the zones required to prevent initiation of cracking, instead of the entire structure has the potential to reduce cooling costs by up to 90%. Finally the issues relating to the dilemma created by the need for longitudinal thermal contraction joints to control the extent of thermal cracks which may occur in high RCC dams in the long term, is discussed and the simple solution devised for the 190 m high Miel I dam, the highest RCC dam constructed in the world to date, is described.
