Safety assessment for different crest raising scenarios of earth dams

This study evaluates the effect of raising earth dams on their safety against seepage and slope stability. A zoned earth dam is considered without a drain, then with a horizontal drain. The effect of the dam raising method is evaluated through two scenarios. Scenario 1 proposes raising the dam’s whole body, while scenario 2 suggests raising the downstream part only, using a retaining wall and downstream backfill. The two scenarios are assessed by raising 10%, 20%, and 30% of the original dam’s height. For scenario 1, different hydraulic conductivities for the raised core were evaluated. For scenario 2, different downstream backfilling materials and slopes were investigated. The results show that dam raising increases the seepage discharge and reduces the downstream slope stability, especially if a high-permeability material is used to raise the core or a low-permeability material is used for the downstream backfill. The importance of the downstream drain is also highlighted.