Hydraulic fracturing: a main cause of initiating internal erosion in a high earth-rock fill dam

ABSTRACTThe Bidvaz dam is an earth-rockfill dam located in the northeast of Iran. About seven and a half years after the start of the first impounding, a subsidence appeared on the  surface of the dam. Evaluation of the dam behavior based on the data recorded by  its instruments confirms the occurrence of internal erosion in the lower parts of the core. Hydraulic fracturing phenomenon has been hypothesized as a main cause of initiating erosion in this dam. Thus, the main purpose of this research was to evaluate the possibility of this hypothesis. To achieve this aim, first the behavior of the dam was simulated with a three-dimensional numerical model. Then, the safety factor against the hydraulic fracturing in the upstream face of its clay core was calculated. The results showed that being located on a steeply sloped narrow valley has caused significant stress transfer from core near the abutments. This has caused the safety factor of these regions against the phenomenon to be less than unity.