Karnafuli Project, Model Studies of Spillway Damage

Abstract

In 1961, the spillway chute of the Karnafuli Hydroelectric Project was damaged by flows ranging up to 3,480 cms (123,000 cfs), about 20% of the design discharge. While not involved with the project prior to the damage, the St. Anthony Falls Hydraulic Laboratory was authorized to conduct model studies of the spillway. It is the objective of this paper to illustrate the damage to the Karnafuli spillway, present information on the probable cause of the damage, and make brief recommendations concerning pressure fluctuations in stilling basins. A separate paper (Toso and Bowers 1988) provides information on a recent study of extreme pressures in stilling basins. The model studies indicated that fluctuating pressures in the hydraulic jump, with magnitudes up to 11 m (36 ft) of head, could have entered the 0.3‐m (12‐in.) drain lines in the chute blocks and caused uplift of the chute slab.