Core crack-filling by upstream gap-graded soils in zoned dams

The crack-filling action in zoned dams, by a granular upstream zone located upstream of a damaged core, was investigated experimentally using the Crack-Filling Erosion Test (CFET). The CFET allows testing specimens with three distinct zones: the upstream zone, the core and the downstream filter. The results of a series of laboratory tests are presented. A total of 34 tests were conducted combining 6 coarse-grained (gap-graded) upstream materials, 2 core soils, and 2 granular filters. The results of the CFETs showed that the crack-filling action is mainly controlled by some of the properties of the upstream zone and of the filter. Core soils with moderately slow erosion, or less erodible, should not have an influence on the crack-filling action. This is so mainly because the filling mechanism should occur over a very short period. The factors influencing the crack-filling by an upstream material are addressed, and some rules which give dam engineers a tool for decision-making about the potential of a upstream material to limit progression of erosion in concentrated leaks are indicated.