B. Steck, E. Robbe & N. Humbert


The experiment conducted at the Lanoux arch dam aims to achieve several goals:


• Evaluation of the interest of continuous ambient vibration measurement on dams for surveillance: while EDF already uses ambient vibration measurement for the calibration of finite-element analyses


under earthquake loads, the interest of this technique for surveillance has not yet been fully covered. This experiment is an excellent opportunity to test material, analyses methods and infrastructures required for long term measurements.


• Pendulums of the Lanoux arch dam showed locally and occasionally particular measurements in winter potentially linked to vertical joints movements. Continuous monitoring of the natural frequencies might


provide interesting information to understand if such behaviour affects the whole dam or remains local.


• Lanoux dam provides a suitable configuration fur such measurements: while located at high elevation in the Pyrénées mountain with rough winter conditions (cold, snow, remote area), the dam is protected


from any human-generated or powerhouse noises and several pendulums’ rooms with power supply are available at the crest to shelter the recording devices.


First, Lanoux arch dam and the experimental setup are presented. Then two methods of analysis have been carried out using the records: using a single-sensor approach with Asterion software and multi-sensor approach with in-house software. Assumptions and initial results for each approach are presented. Finally, a synthesis of the first results is proposed with the first feedback regarding the chosen experimental setup.


2. Dam and Ambient Vibration Measurement Setup Presentation


2.1. Dam presentation Lanoux dam is a double curvature, 42.5m high arch dam, which is asymmetric due to the shape of the valley. Owned by EDF, it is located in the southwest of France. It was constructed between 1957 and 1960, built in 13 blocks. In Figure 1 and Figure 2, illustrations of the dam are presented. The foundation of the dam consists of laminated metamorphic slate with a high compressive strength. However, the anisotropy of the foundation confers a higher deformability to the left bank.


Figure 1. Downstream view of the dam: recording devices are located in the pendulum rooms near the crest of the dam


142 | Dam Engineering | Vol XXXIII Issue 3


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