Page - 998 - in Book of Full Papers - Symposium Hydro Engineering

Fig.1. The right abutment strata along dam axis By considering the geological and geotechnical investigations and analyses of laboratory and field test, the right abutment strata, the alluvial terrace under clay core foundation in right abutment must be removed and replaced by a key trench as sealing element since the fine grained material of this abutment is generally classified as low to very low permeable material. Ahmadbeiglu Dam and cofferdam are both earth fill with vertical clay core. Minimum, normal and maximum water levels in the reservoir are levels 971.5 m, 1010.0 m and 1013.3 m, respectively. The total reservoir volume is 27.4 Mm3. The dam crest is 10 m wide and 528 m long at elevation 1016 m. The maximum dam height is 58 m from riverbed and 65 m from foundation. The upstream slope is 2.5 H to 1.0 V from dam crest to elevation of 991 m, which corresponds to the stabilizing berm with 10 m width, then, continue with the same slope to natural ground. The downstream slope is 2.0 H to 1.0 V. The upstream and downstream slopes of cofferdam are 2.5 H to 1.0 V and 2.0 H to 1.0 V, respectively. 3. INTERNAL EROSION RISK ANALYSIS METHODOLOGY The internal erosion risk analysis in right abutment of Ahmadbeiglu earth fill dam has been carried out in accordance with the methods of ‘’Dam Safety Risk Analysis Best Practices, 2009’’. In this paper, the risk analysis is limited to evaluation of internal erosion in normal operation and the other loading condition (flood and seismic loading) has not been considered. The risk analysis process consists of a) Identification of failure modes b) Estimation of probability of dam failure due to each failure modes c) Dam failure 998