Evaluating the reliability of earth dams according to the second group of limit states (Method of predicting dam behavior)

Abstract

1. The use of the method of summation of resistances along the path of a concentrated seepage flow permits a rather rapid evaluation of the reliability of a layered dam both from the viewpoint of the presence of eroding velocities in the cavity of a possible crack and with respect to the permissible level of discharges through the dam. 2. When cracks occur in the core in which the flow velocities exceed the level of noneroding velocities phenomena of reworking (rewashing) of the core material and filling the crack cavity with the coarse-grained material adjacent to the core on the upstream side occur under certain conditions. For the Boulderhead dam these phenomena are substantiated by calculation and confirmed by the discovery of zones of segregation of core material during an inspection of damaged parts of the dam [4]. 3. The method of evaluating the reliability of layered dams (with a core or facing) according to the second group of limit states (according to the level of velocities — discharges and limitation of the opening of cracks as a consequence of clogging) makes it possible to refine the prediction of the behavior of existing dams and to make more economical and reliable design decisions. 4. The proposed calculation methods for predicting the behavior of earth dams can be regarded to some extent as confirmed by the two full-scale experiments on high dams.