Une nouvelle technique d'inclusion pour la mesure à long terme des déformations dans des barrages en béton

This paper presents the results of an experimental study on the development of a simple yet efficient technique allowing for the long-term measurements of strains and stresses in working concrete dams. The proposed technique consists of installing a cylindrical concrete inclusion instrumented with vibrating wire gauges embedded into the concrete. The 140-mm cylinder is slipped into a 152 mm diameter hole, which is drilled into the dam and then filled with cement grout. This technique, which was tested in the laboratory on instrumented concrete blocks, has shown that it is now possible to measure the deformation variations in a working dam. The inclusion can be instrumented for both bidimensional and tridimensional cases. The volume of the cylinder makes room for a sufficient number (4–8) of vibrating wire gauges. Moreover, during the drilling process, the technique of overcoring makes it possible to determine the initial total stresses. This technique can also be used to instrument heavily loaded rock structures such as mine pillars or underground gallery walls. Current observations show that this technique, contrary to plastic inclusions, can be considered appropriate for permanent structures. Key words: vibrating wire gauges, strain gauges, instrumentation, strain measurements, long term, concrete dams, rock slopes, rock pillars, mines, underground excavations.