Rollcrete gravity dams and methods of its tiered construction

Conclusions

• 1. To eliminate the joint between the upstream zone of ordinary concrete and internal zone of rollcrete, a design of a gravity dam is proposed with the construction of a sawtooth joint between these zones, which is obtained by tiered placement at first of 2–4 layers of rollcrete and then concrete of the upstream zone with the use of the layerwise method. The joint of the two types of concrete is carried out through the inclined area of undercompacted lean concrete, which is formed naturally along the slope of 2–4 layers of lean concrete mix having an average gradient of 1∶0.1 toward the upstream pool. On the next tier up the joint of the two concretes is shifted toward the upstream face, which creates localness of the undercompacted areas of concrete and, on the whole, the sawtooth shape of the contact of the upstream and internal zones of the dam.

• 2. On the downstream face it is suggested to protect the rollcrete with an insulating layer made of triangular precast reinforced-concrete elements, inside which is located insulation. The tiered installation of the precast elements with rolling of 2–4 layers of lean concrete on them creates the sawtooth joint between the internal and downstream zone of the dam, providing minimum effects of the outside air temperature fluctuations on the load-bearing profile of the structure.

• 3. The proposed design of the dam allows uniform tiered placement of the concrete, and two methods of concreting: rolling of the lean concrete and vibration by the suspended packet vibrators can be separated within the tier so as to maximally simplify the technology of constructing the dam. The layerwise method of concreting the upstream zone of the dam and the method of rolling the lean concrete in the internal zone coincide in many technological operations, which on the whole enables their successful combination when constructing the dam and creates favorable conditions for providing solidity of the structure.

• 4. In further investigations it is necessary to calculate the stress state of the dam with variation of the location of the contact between the zones of concrete of different type in plan and over the height. In a particular development of the design of a dam with a downstream insulation zone, investigations of the effect of the thickness of the insulation zone on the calculated profile of the dam, accompanied by the selection of the type and thickness of the insulation material in relation to the climatic conditions of the construction region, will also be required.