Risques d'effondrement de carrières souterraines en milieu urbain. De la prévention à la mise en sécurité. Exemple de l'îlot St-Julien à Laon (02)

Abstract : Since the autumn 2001 the city of Laon has of a Plan of Prévention of the Predictable Natural Risks concerning potential ground instabilities. The risk of collapse is connected to the présence of abandoned underground cavities located in lutetian limestones constituting the upper hard level of Laon's hillock. In the "St - Julien" district, the historical town centre, the Municipal Service of the Careers noticed disorders with evolutionary character affecting the buildings at ground level and the corresponding underground works . A geotechnical analysis established that the origin of thèse disorders is directly linked with the failure of galleries excavated in the levels of glauconian sands situated at the base of the calcareous benches. In order to garanty the security of people and structures in surface, one has to proceed to the treatment of the subsoil by privileging the backfilling of the cavities at the origin of the disorders. However thèse works take on a particular technical character because of the urban environment, especially the présence in galleries to be treated of a thick layer of anthropological organic matter (these galleries having been used until recently as septic tanks) more or less solidified and probably very compressible. Several solutions were studied to operate a consolidation of galleries by concrète injection in several phases, by considering that the layer of excréments has a capacity of consolidation comparable to a peat. Then, the galleries of the upper levels can, according to their state of dégradation, either be backfilled with expansive resin foam, or Consolidated (masonries, hoopings ...), so as to be reused.
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  • HAL Id : ineris-00961865, version 1
  • INERIS : PU-2002-124

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Jean-Marc Watelet, D. Montagne, Michel Wojnarowicz. Risques d'effondrement de carrières souterraines en milieu urbain. De la prévention à la mise en sécurité. Exemple de l'îlot St-Julien à Laon (02). Revue française de Géotechnique, 2002, pp.35-41. ⟨ineris-00961865⟩

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