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2021-10-09 - Colloque/Présentation - communication orale - Anglais - page(s)

Georgieva Temenuga Dimova , "Geomechanical evaluation of an abandoned chalk mine using in-situ measurements" in EuroEngeo, Athens, Greece, 2021

  • Codes CREF : Sciences de l'ingénieur (DI2000), Travaux miniers souterrains (DI2323), Résistance et comportement des matériaux (DI2110), Mécanique des roches (DI1418), Essais non destructifs (DI2832), Exploitation des mines et carrières (DI2320), Déformation, rupture matériaux (DI2113)
  • Unités de recherche UMONS : Génie Minier (F408)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux), Institut des Sciences et du Management des Risques (Risques)
  • Centres UMONS : Ingénierie des matériaux (CRIM)

Abstract(s) :

(Anglais) The Malogne site is an abandoned underground phosphatic chalk quarry located in the Mons Basin (Belgium) mined out at shallow depth by the room-and-pillar method. With its 67 ha total area the site is situated very close to important surface infrastructure and residential houses. During and after its exploitation several significant ground collapses were registered. The last one from 2015, with an area of 1.2 ha and a maximum amplitude of 3 m, occurred close to the railway Brussels-Paris affecting agricultural land. To characterize the geomechanical conditions of the underground openings in the central part of the quarry the Geological Strength Index (GSI) (Hoek et al., 1995; Marinos et al., 2005) and Rock Mass Rating (RMR89) (Bieniawski, 1989) classification systems were applied. The discontinuities characterization is based on a structural survey (293 measurements). The geomechanical evaluation of the massif is realized by a set of parameters as the Joint Roughness Coefficient (in 39 profiles), the Rock Quality Designation (in 8 locations) and the Intact Rock Strength (in 356 points). Due to the seasonal groundwater level fluctuation in the studied area three zones are differentiated - dry, transitional and water-saturated which is not accessable for observations. As a result, of the annual variations some of the pillars are exposed to cycles of water saturation and drying. Considering the most unfavorable rock mass conditions three geomechanical zones were identified in the studied area (Figure 1). Those connected with Good to Fair rock mass (classes II and III) are typical for the dry parts of the quarry while the Poor one (class IV) is mainly related to the transitional zone. An exception of that is a narrow elongated area of rock mass class IV in the western part of the site that follows the faulted zone. The rock mass next to the collapsed sector was also classified as Poor.