Georex (France)

Every year, around 20 sinkholes occur in France above former mining galleries or works. Some of those sinkholes significantly impacted buildings and jeopardised public safety. As part of a risk prevention strategy falling under the responsibility of the French national authorities, the public institution GEODERIS, which is in charge of the post-mining risk expertise, has developed and implemented, for over the past decade, a methodology to assess and map sinkhole hazards and risks. This approach focuses on assessing the building fragility subjected to sinkhole hazards. The methodology was developed in collaboration with the Scientific and Technical Centre for Building (CSTB), the public institution in charge of research and development in this field and is based on a representative sample of 210 buildings across various French cities. Seven building types and five categories of load-bearing structures were first identified. Owing to analytical simulations of a load-bearing structure behaviour subjected to sinkholes of increasing diameters, a damage curve was derived. The risk level is assessed according to the expected damage building percentage relative to the expected sinkhole’s surface area. Between 2012 and 2015, around 3,000 buildings located in sinkhole hazard zones across French territory were listed. This method made it possible to eliminate the safety risks for half of these buildings. Mining works under buildings rated at medium-risk or high-risk are nowadays either being monitored or have been secured. The proposed methodology discriminates between situations that could impact buildings from those that could jeopardise public safety. It provides to the authorities in charge of post-mining risks prevention a coherent approach for optimal decision-making.

Le rôle du substrat dans le maintien des caractéristiques morphologiques des myocytes isolés de coeur de rat adulte et maintenus quiescents en survie pendant 4 à 5 jours a été étudié par immunomarquage de protéines du cytosquelette.Lorsque l'adhésion est effectuée en présence de sérum de veau foetal (4% pendant 3 heures), seuls sont fixés les myocytcs ayant conservé leur forme rectangulaire, ie non lésés lors de la procédure d'isolement.Après 5 jours de culture en milieu défini (Milieu Wissler BM 86, sans sérum), 50°Io des myocytes conservent leur forme initiale mais leur activité de synthèse protéique diminue (-20%).Les marquages de l'a-actinine et de la desmine révèlent le maintien des structures myofibrillaires et leur parallélisme strict.Les microtubules, normalement concentrés autour du noyau et organisés en un réseau lâche, deviennent particulièrement abondants au niveau des extrémités cellulaires qui ont tendance à s'arrondir.L'adhésion des myocytes sur laminine (20 !tg/ml) entraîne une augmentation de la densité cellulaire.Après 5 jours de culture, les myocytes s'étaient et développent des excroissances riches en microtubules et en filaments intermédiaires.L'aspect de ces cellules devient alors proche de celui des myocytes néonataux cultivés.Leur recouvrement avec du MatrigeI R diminue l'importancc du processus de dédifférenciation.Cette étude contribue à mettre en évidence l'importance du substrat d'adhésion dans les changements morphologiques survenant chez les myocytcs adultes in vitro.