Seite - 1254 - in Book of Full Papers - Symposium Hydro Engineering

COMMISSION INTERNATIONALE DES GRANDS BARRAGES ------- VINGT-SIXIÈME CONGRÈS DES GRANDS BARRAGES Autriche, juillet 2018 ------- RISK BASED APPROACH AT THE DAM SAFETY ASSESSMENT DURING ITS RECONSTRUCTION Jaromír ŘÍHA, Miroslav ŠPANO Water Structures Institute, BRNO UNIVERSITY OF TECHNOLOGY CZECH REPUBLIC 1. INTRODUCTION The management of floods is of fundamental importance for dam safety. Overviews mentioned in Bulletins [8] and [9] indicate that flood events have been the main reasons for dam failures. According to the recommendations of the International Committee on Large Dams (ICOLD) the dam safety criteria have been significantly stiffened, namely in terms of the design and check flood probabilities related to spillway capacity. In the Czech Republic the criteria were implemented into the decree No. 367/2005 Coll. [6] which was incorporated into the standard CSN 75 2935 [3]. At recent time a wide and systematic reassessment of dams´ hydraulic safety have been performed over the whole country. Common result of the assessment is that the dam does not comply with new requirements and should be upgraded as soon as possible. The experience based on numerous case studies and re-assessments of dam safety in the Czech Republic shows that the crucial problems lie in insufficient spillway capacity, low elevation of clayey core due to imperfections during the construction and also dam settlement and also in lower dam crest than required in terms of prescribed freeboard. One of the reasons of inadequate dam parameters are also less strict requirements on hydraulic safety of dams in the times of their construction. The reconstruction of the above mentioned dam components practically always calls for provisional disassemble of the dam crest and also significant intervention into the spillway entrance profile and chute line. The crucial question 1254