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Nantes, France

Gueguen P.,Joseph Fourier University | Semblat J.-F.,UPE | Bard P.-Y.,Joseph Fourier University | Chazelas J.-L.,UNALM
Bulletin des Laboratoires des Ponts et Chaussees | Year: 2013

At the scale of a city, surface structures such as buildings can modify the "free field" seismic motion and act like secondary seismic sources. A number of observations have been conducted on actual datasets; these have demonstrated that such an effect may indeed be significant. The direct consequence of this "site-city interaction" is the contamination of seismic motion in an urban setting by a secondary wave field. Both centrifugal and numerical modeling efforts tend to confirm that this phenomenon is not incidental. More specifically, results indicate that between two buildings located close to one another, interactions occur that modify not only the soil movement but also the response of structures subjected to the movement. At the scale of a city, this phenomenon will become even more pronounced whenever strong coupling exists between the soil response and the response of the urban environment. Source

Mauduit V.,Interdepartementale des Routes du Massif Central | Mauduit C.,CETE de Lyon | Vulcano-Greullet N.,DREAL Bourgogne | Coulon N.,CETE de Lyon | And 5 more authors.
Bulletin des Laboratoires des Ponts et Chaussees | Year: 2013

In light of the damage witnessed on France's road network over these past several winters, network managers and the scientific community have been seeking to understand the phenomena at play in order to prevent against such degradation. The research undertaken between 2006 and 2009 by the "water-freezing" working group as part of LCPC's Fondephy research project has allowed for an in-depth investigation of a few field cases and the generation of leads for future studies regarding the damage mechanisms capable of taking place over both the long and short term. Among these mechanisms, the phenomenon of sliding, recently observed on the Nantes pavement fatigue carrousel, has been noted between wearing course and foundation layer; this finding has altered the generally held perception of pavement operations specific to the overlaying of bituminous layers and may justify a fatigue occurring over the upper part of the pavement, exacerbated at higher temperature. From another perspective, the phenomenon of swelling of frozen asphalt mixes exposed to partial water saturation could also be explored thanks to recent observations during laboratory experiments that had been inspired from soil freezing/thawing test campaigns. This mechanism may give rise to the sudden appearance of potholes at the pavement surface when exposed to winter weather conditions. Source

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