Analysis of a geomembrane face rockfill dam during earthquake loading

The paper represents an analysis of the suitability of a geomembrane face rockfill dam in highly seismic area. This rockfill dam type has a geomembrane for watertightness on its water side with geotextile and thin layers of filter materials on both sides to protect it. The rockfill dam is a part of three proposed hydropower schemes in the lower part of the pjórsá glacial river in SW-Iceland. The hydropower plants and all related structures are situated in the South Iceland Seismic Zone where two major earthquakes of magnitude 6.6 and 6.5 (M _W) with a registered peak ground acceleration of 0.84g occurred in June 2000. Further a 6.3 event occurred in 2008. The analysis of the dam is split into two parts. Firstly the stability of the dam is determined with the method of slices. Secondly the finite element method is used to estimate the deformations induced by earthquake loading where the behaviour of the geomembrane and the surrounding soil is given special attention in regards of possible slipping. The main result revealed that the proposed dam will withstand the earthquake load without major damage or total collapse. Largest relative deformations along the geomembrane, caused by the applied earthquake loads, have been estimated to be approximately 60 cm. These deformations are rather large but since they are local, the total stability of the dam is not threatened. A necessary repair would though have to be carried out in the occurrence of such an event.