EXPERIMENTAL INVESTIGATION OF SPATIAL VARIABILITY OF GROUND MOTIONS – MONITORING OF AN ARCH DAM

International audienceThe term " spatial variability of seismic ground motions " denotes the differences in amplitude and phase content of seismic motions recorded over extended areas or within the dimensions of a structure. The effect of such spatial variability on the response of civil infrastructure systems such as dams is still an open issue. In-situ experiments may be helpful in order to answer the questions regarding both the quantification of the spatial variability of the ground motion within the dimensions of a structure as well as the effect on its dynamic response. For this purpose, the 69-m-high double curvature Saint Guérin arch dam located nearby the village of Beaufort, Savoie, France as well as the surrounding area is instrumented with a seismological network with a few meters of inter-station distance. This very dense network consists of nineteen velocimeters which have been deployed for one year in total (June 2015-June 2016). The configuration of the network is such that the spatial variability of the ground motions can be captured on the dam-foundation rock interface (left and right side of the valley) and at the surrounding area. Coherency functions are computed and analyzed providing information about the effect of the on-site topography and the interaction with the dam on the ground motion. Besides, the measurements along the crest provide informations on the structure's response that might be useful for the interpretation of the results