Reliability of rock foundations of concrete dams

Abstract

1. Dam failures are impermissible, since the consequences of the destruction of even a small modern dam with respect to the number of victims and material losses can be analogous to the action of a natural catastrophe and inflict incalculable social damage. 2. The statistics indicate that the number of dam failures before 1930 was 13.8% of those constructed and during the period from 1931 to 1970 8.5%, including 2.2% for concrete dams on rock foundations, of which 0.3% — the risk of destruction and 1.9% — the risk of damages. To develop measures to increase the reliability of dams, failures should be examined separately according to the types of structures and their foundations. A characteristic feature of the failures of concrete dams on rock foundations is that the majority of their failures after 1930 are related to the dam foundations. 3. The reliability of the constructed structures can be estimated on the basis of the general method of analyzing failures based on the use of a multifactor model. The use of this method permits taking into account both external factors and estimating the reliability of the dam-foundation system. Such an approach made it possible to establish that 64.8% of failures from the action of external factors occurred during filling of the reservoir; 27.8% occurred as a result of floods; 5.7% were related to earthquakes; and 1.7% were due to the effect of temperature. 4. Failures should be analyzed on the basis of a thorough study of each individual failure corresponding to their grouping according to levels of significance and groups of failures.