Deformation of the rock foundation of the Bratsk hydroelectric station

Conclusion

Deformations of the rock foundation of the Bratsk dam occurred mainly during filling of the reservoir and primarily due to the weight of the water operation. During operation, settlements have increased insignificantly with a clear tendency toward their fading away. The maximum settlement, 74 mm, which had been predicted as early as 1966, was reached in 1970; in 1977 it amounted to 74.4 mm. Horizontal deformations have practically stabilized.

At the base of the dam, if slight consolidation occurred at all during construction (which, apparently, caused mainly differential settlement of the sections), then it was hardly noted by observations.

Despite the explicit stabilization of the processes, observations of settlements and horizontal displacements retain their importance, considering the essential character of the structures, the seismicity of the region, and the slowness of processes characteristic for hydraulic structures. The geodetic base of the Bratsk hydrostation has certain shortcomings: the bench marks are located on a diabase sheet and can settle along with it; the nearness of the diabase rock quarry to the right-bank bench marks; the rather long and complex traverse along the foreshores. Use of the geodetic base is also difficult: the traverses along the foreshores are difficult and dangerous owing to the adjacent high (up to 80 m) steep cliffs, the natural disintegration of which causes rock falls.

We consider that it would be more convenient and reliable to embed bench marks with anchors in sandstones below the upper zone of consolidation (depth 100–120 m) in the bank tunnels of the inspection gallery at the 27-m level.