Lessons learned from dams behavior under earthquakes

Abstract

It is important to analyze embankment dam behavior from the past lesson slearned. It is noticed that modern embankment dams withstand the design earthquake without significant damages. In spite of this scenario it is important to prevent the occurrence of incidents and accidents of embankment dams under earthquakes and so a deep understanding of the triggering factors is needed. Well documented case histories from different regions of the world related with embankment dam behaviour were carefully selected and are discussed. The design and the analysis of dam stability under seismic conditions are addressed. The new trend for performance basis design is to consider 2 levels of seismicactions and to analyse the situation when the limit of force balance is exceeded for high intensity ground motions associated with a very rare seismic event. The reservoir triggered seismicity (RT S) is linked to dams higher than about100 m or to large reservoirs (capacity greater than 500 × 10 6 m 3), rate of reservoir filling and to new dams of smaller size located in tectonically sensitive areas. Dam monitoring and inspections of dams are presented. Experience has shown that the rational and systematic control of dam safety should consist of several tasks: (i) regular instrumentation measurements; (ii) data validation; (iii) data storage; (iv)visual inspections; (v) safety evaluation; (vi) corrective actions. The risks associated with dam projects are discussed. The potential risk associated with dams consists of structural components and socio-economic components. The structural components of potential risk depend mostly on storage capacity and on the height of the dam, as the potential downstream consequences are proportional to the mentioned values. Socio-economic risks can be expressed by a number of persons who need to be evacuated in case of danger and by potential downstream damage. It is important to develop new ways of thinking and strategies to address the future challenges.