Page - 17 - in Book of Full Papers - Symposium Hydro Engineering

COMMISSION INTERNATIONALE DES GRANDS BARRAGES ------- VINGT-SIXIÈME CONGRÈS DES GRANDS BARRAGES Autriche, juillet 2018 ------- OBSERVATIONS OF PERFORMANCE OF EARTHFILL EMBANKMENTS DURING RECENT EARTHQUAKES IN NEW ZEALAND Trevor MATUSCHKA Director, ENGINEERING GEOLOGY LIMITED NEW ZEALAND 1. INTRODUCTION Many earthfill embankment water storage dams have been constructed near Seddon, New Zealand since 2004 for the purposes of irrigating grapes. They range up to 26m in height. They were subject to very strong earthquake ground motion from earthquakes in 2013 and 2016. Peak horizontal ground accelerations of close to 0.75g were recorded at Seddon during the Mw6.6 Lake Grassmere earthquake (16 August 2013) and the Mw7.8 Kaikoura earthquake (14 November 2016). The performance of eleven water storage dams located near Seddon that were subjected to these two earthquakes is summarized. The embankments were generally designed in accordance with guidelines published by the New Zealand Society on Large Dams (NZSOLD). 2. OBSERVATIONS Observations of embankment performance are summarized in Table 1. In general, there was minor to no damage to dams that were designed and constructed to modern standards. Some dams were affected more by the Lake Grassmere earthquake. This is explained by this earthquake being closer, even though the Kaikoura earthquake had a much longer duration of strong shaking. 17