Page - 154 - in Book of Full Papers - Symposium Hydro Engineering

for a 38.1-cm (15-in) slab thickness with 7.6-cm (3-in) reinforcing bar cover and 17.8-cm (7-in) drain pipe cover. The construction documentation indicates that some of the large aggregate caused breakage of the herringbone drain pipes as the concrete was being placed. Although it is believed that broken drain pipes were repaired when they were observed during construction, there may be other locations where pipes were damaged during concrete placement but the damaged pipes were not observed and were not repaired. Fig. 6 Foundation preparation in the vicinity of the initial slab failure. Note what appear to be extensive areas of soil-like materials in the foundation. 2.6. SERVICE SPILLWAY CHUTE SLAB REPAIRS The service spillway chute slab concrete has been repaired numerous times since the original construction. Documented repair efforts occurred in 1977, 1985, 1997, 2009, and 2013. It is possible that there were other undocumented repair efforts. The observed spillway chute damage that led to the repairs was caused by various different mechanisms including cracking, removal of joint filler, delamination, and spalling. The cracking occurred predominantly over the herringbone drains. These cracks were first documented in a 1969 report [4], which 154