Sharif University of Technology Civil Engineering Department Tehran-Iran Dam Safety An Approach to Prevent Dam Incidents

Dam failure results in a catastrophic break followed by a flood wave often with considerable loss of life or property Safety during Design, Construction, Operation, Maintenance, and Surveillance of dams Past incidents of unacceptable performance can help us in understanding of method of detection and expand our knowledge on behavior of dams and reservoir and this simulates further improvements in design, maintenance and surveillance of dams

Main causes of Dam Failure Failure of Concrete Dams Lack of shear strength and discontinuity in foundation Excessive uplift in the foundation (inadequate or non-existent drainage) Lack of dam stability Excessive or differential deformation of the foundation Piping and erosion in the foundation caused by high permeability Flaw in design Lack of supervision during construction No monitoring or warning system (systems were out of order) Cont. next page…

Main causes of Dam Failure Failure of Concrete Dams (cont. ) Human error during site investigation and design and construction and operation Inadequate foundation investigation Incomplete data on available material Poor design Negligible construction supervision Incomplete first impoundment Incorrect operation of flood gates Insufficient monitoring and data analysis Lack of preventive measures or repair work

Main Causes of Dam Failure Embankment Dam Failure Overtopping during flood discharge because of inadequate spillway capacity or non-functioning flood gate Internal erosion along the dam-foundation interface or along embankment with adjoining or embeded appurtunent structures or concentrated piping in the embankment itself because of inadequate or non-existent filter zones Nonhomogeneity in the foundation or dam (leading to foundation failure or erosion ) Large settlement in the foundation Crack following the settlement, with resulting piping effect liquefaction

Failure Prevention Failure could have been prevented if some of these points had been observed Failure is a complex process Begins with some abnormality in behaviour (not detected) Consequent deteriorations (not observed) Further damage or disaster Inspection and Monitoring of dams as well as data analysis and interpretation has a critical role in the field of dam safety

Dam Safety Guidelines Intended to offer a comprehensive review: Dam -design -operation -construction –maintenance -surveillance Recommendations rather than binding regulations Guidelines are not standards Details dealt with as necessary

Dam Safety Procedure (adapted for Iran) Dam Safety Procedure General Plan Monitoring Consultant Companies Emergency Action Plan (EAP) Periodic Dam Safety Review Dam Retrofitting Owner

MONITORING Instrumentation and Surveillance External and internal examination of dams during their life time Long term surveillance program Ensure dam’s owner of their safe operation Monitoring Measure Displacement Settlement Strain Piezometric pressure Seepage Uplift Water level Alarm System Compilation of Results, Interpretation, Recommendation, To take appropriate action

MONITORING Instrumentation To characterize dam site and dam structure condition To verify Design To asses safety To asses performance

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