Session K.pdf - Clarkson University

shown (Figure 4). Along the front crest face (site 2) in the winter of 2002/2003, therewere cracks in the ice due to the headwater level variation not exceeding 10 cm, whilethe ice and frozen Fusegates on the crest remained fixed.HPP has started operating in winter 2003/2004. By the end of January, inflow dischargebecame less than the discharge of two turbines and the headwater level decreasedby 15 cm below labyrinth crest level. Two cracks formed in front of the Fusegatesand the ice broke off the frozen Fusegates (Photo C and figure 7). Then one ofthe turbines stopped and headwater level started rising. No new cracks were formedand ice displacement occurred along the existing cracks as the ice was less solid andhad less strength compared to solid ice. During all this period, no fusegate displacementwas observed. Ice thickness in this period was more than 30 cm.Photo C. Ice cracks in front of Hydroplus FusegatesIce thickness is more than 30 cm and level fluctuation about 15 cm(February 2004)Fig. 7. Cracks Development SchemeDuring the water level raising, flowing over the labyrinth crest started again. With hardfrost and small discharges, both the vertical and the sloped labyrinth sides became encrustedwith ice under the overflowing nappe. In case of Hydroplus Fusegate crest overflowing,such ice can considerably increase the tilting moment and reduce Fusegatesstability. Therefore winter monitoring is on going regarding this matter.357