Construction-flow diversion and general scheme of Hoabinh hydraulic development dam construction

Abstract

1. The adopted scheme for discharge of the construction flows through the Hoabinh hydraulic development site has proved to be reliable, and it can be recommended for construction of hydraulic projects under conditions with seasonally repeated rain floods and a clearly defined and stable low-water period. 2. The combined scheme for discharge of the flows through the diversion tunnels and canal made it possible to carry out the work in the diversion canal zone for construction of the dam fills, grouting of the dam base, and other work, with subsequent discharge of the rainy season flood through the diversion canal at increased levels. 3. Construction of the temporary concrete spillway at the end of the canal in the zone in which the downstream wedge of the dam ends made it possible to discharge the 1986 floods with a peak flow of 14,500 m3/sec and with a specific discharge of 180 m2/sec (the maximum over the construction period) without damage to the dam fills, since the scouring velocity was developed beyond the downstream structure limits. The constructional solution for discharge of the river flows through the partially constructed rock-earth dam can be recommended for use in the hydraulic engineering practice. 4. Use, in the construction flow discharge scheme, of the deep sluices of the spillway head structures, located approximately in the central part of the dam height, can be recommended as a permanent or temporary solution for similar cases.