Evaluation of the total opening of cracks in the contact zone of the bed of the dam for the Sayano-Shushenskoe hydroelectric power plant during impoundment of the reservoir from the midsummer operating level to the normal surface level

The design organization could not have contemplated the scale of the loosening of the rock mass, as a result of which the lower surface of the dam and the contact zone of the foundation bed were not instrumented to the degree necessary for direct measurments of openings and loosening in the contact zone.The readings of available slit gages are insufficient for estimation of total openings.Lower and upper estimates of the openings in the contact zone near the thrust face are obtained from readings of transverse hydrolevels. It is understood from geometric representations that even for several horizons, the total opening cannot exceed the vertical component of the displacements obtained as a result of inclination of the lower surface.In addition to estimates of maximum expected openings, the fact of the “in-leakage” of these values from year to year is of interest. Estimating this process for the period from 1991 through 1997 from hydrolevel readings, we obtain an additional opening of from 2.3 to 4.4 mm in section 33 (according to minimum and maximum estimates). This process proceeds more vigorously under the spillway portion of the dam than beneath the powerhouse portion, and it is especially noticeable beneath section 45.