On-site investigations of the contact zone of the upstream face of the concrete dam on the Ust-Ilim hydroelectric station

摘要

1.The conditions of the contact zone under the upstream face of the Ust-Ilim dam depended on the design features of the sections and temperature regime during filling of the reservoir. The maximum propagation of the contact crack to 13 m occurred in the powerhouse sections still before linking with the powerhouse with open conduits that communicated with the outside air. The continuity of the contact under the upstream face was not disturbed in the powerhouse sections linked with the generator room in the first year of filling the reservoir.2.In theoretical investigations of the boundaries of decompression of the foundation of the contact zone under the upstream face of a gravity dam it is necessary to take into account: a) stresses (strains) of the construction period; b) effect of the shape of the offset profile; c) temperature regime of various types of sections.3.Vertical cracks in the concrete of the contact slab of the temporary dewatering outlets occurring in the construction period can become paths of concentrated seepage. This should be taken into account when designing the underground contour of a dam analogous to the Ust-Ilim.4.The uplift in the foundation of the Ust-Ilim dam is considerably less than the design. This is evidently related to the low permeability of the diabases and additional draining of the foundation under the upstream face. However, according to the experience with the Bratsk dam we can assume that the established seepage regime in the foundation can change with time. The combined effect of the hydrostatic load and seepage forces in the presence of seasonal variation of the thermal stresses in the contact zone can lead to a gradual increase of uplift.