PERFORMANCE OF A FILL DAM BASED ON THE PERFORMANCE-BASED DESIGN CONCEPT AND STUDY OF A SEISMIC RETROFITTING METHOD

摘要

Fill dams have long been designed by conventional specification based design methods which stipulate details concerning dam body materials, structural calculation methods, and construction methods. There are irrational aspects to applying the specification based design method to a case subjected to large earthquake such as the 1995 Hyogo-ken Nanbu Earthquake, a type that rarely occurs. Thus, since the Hyogo-ken Nanbu Earthquake, the concept of performance-based design that treats performance of a structure as the only requirement has been incorporated, and conventional specification-based design is now being replaced by performance-based design based on required performance as the design method for structures. When an earthquake strikes a fill dam, water in the dam must not overflow the dam body causing a severe disaster in the area downstream from the dam. It is, therefore, necessary that settlement at a dam crest during an earthquake does not exceed a critical value, requiring that it be designed by an analysis method capable of accurately predicting the quantity of settlement produced. This report describes a design study of a fill dam, which requires a high level of seismic performance because of its location conditions and functions. Performed by applying the concept of ISO23469 to an existing fill dam, the study focused on ① setting performance criteria, ② evaluating safety of a fill dam during an earthquake, and ③ reinforcement method that satisfies the performance criteria and evaluation of its safety.