Hydraulic filling of dams constructed of silty soils, using a flattened profile

Abstract

1. Construction experience and experimental investigations established that it is advantageous to use silty soils for the construction of dams with a flattened profile, consisting of a downstream impervious shoulder (hydraulic fill) and upstream wave-resistant ramp (dumped material). This design eliminates the construction of massive shoulders of gravel-pebble material which are needed in hydraulic filling of compressed dams of disperse soils. 2. Flattened dams, depending on the content of sand particles in the disperse soils, are constructed by unilateral hydraulic filling with limitation of the upstream slope or by unilateral hydraulic filling with bypass of the soil-water mixture into settling pools arranged on the section of the upstream ramp. With both methods the stability of the dam is provided during construction by layerwise consolidation of the soil. The wave-resistant ramp, constructed beforehand by dumping soil, eliminates the need of an upstream slope revetment and provides stepwise filling of the reservoir. 3. In the case of unilateral hydraulic filling with bypass of the soil-water mixture into settling pools the quality of the soil placed in the impervious shoulder improves. In this case the carry-off of soil with the drain water does not exceed 5%, whereas with hydraulic filling by the old technology carry-off averaged 25% 4. The cost of constructing a flattened dam for a height up to 15 m is about 3% less than the cost of a compressed dam with gravel shoulders, and with consideration of the reduction of soil carry-off the construction cost is reduced additionally by 10–15% in the case of hydraulic filling by the recommended technology with placement of settling pools on the section of the upstream ramp. 5. In hydraulic filling of dams by the recommended technology labor productivity increases 19% owing to the reduction of soil losses and decrease of manpower. 6. When planning construction operations, it is necessary to take into account the basic parameters characterizing the technological process: rate of hydraulic filling designated so as to provide layerwise consolidation of the soil and calculated by Eq. (1) and the optimal layers of hydraulic fill and dumped soil in the settling pools, determined by Eqs. (5) and (6).