Stress Distirbution Variations between Two and Three-Dimessional Analysis of Bakcfilled Stopes

M. Shahsavari, M. Jafari, M. Grabinsky

Dans les comptes rendus d’articles de la conférence: GeoOttawa 2017: 70th Canadian Geotechnical Conference; 12th joint with IAH-CNC

Session: Mining - Underground and Backfill

ABSTRACT: Mined out voids (stope) are usually backfilled to provide support for further excavation and reduce the volume of surface disposed mine tailings. Over the past decade, cemented paste backfill (CPB) has gained popularity over other backfilling materials due to its high delivery rate and tight characteristics. Fresh CPB is held in the stope by a barricade that is built at the draw point. Safe and economic design of the barricade is dependent on a proper knowledge of stress distribution within the backfilled CPB. These stresses are dependent on pore water pressure and the degree of arching that occurs between CPB and the much stiffer surrounding rocks. Most of the previous studies to incorporate arching into the prediction of barricade forces were either one or two-dimensional (e.g. Doherty and Muir Wood, 2016; Shahsavari and Grabinsky, 2016; and Mkadmi et al., 2013). Fahey et al. (2009) compared the arching degree that occurs in plane-strain and axisymmetric 2D simulations and provided guidelines so that both geometries would yield the same degree of arching. However, these analyses were never compared with a full 3D analysis. In the current study, a 3D stope backfilling scenario is simulated using FLAC3D and the results are compared with 2D plane-strain approximations. The transient pore pressures are also incorporated into the analysis. For the sake of simplicity of the analysis and emphasis on the role of arching on the barricade stresses the effect of cement hydration is ignored. Finally, recommendations are made on how to properly approximate the 3D simulation with a proper 2D plane-strain analysis.

RÉSUMÉ: quantité de résidus. Durant la dernière décennie le remblai à pâte cimenté (RPC) a été de plus en plus utilisé grâce à son puisage. La conception sécurisée et économique relative à la barricade est dépendante sur la connaissance de la se produise entre le RPC et la roche beaucoup plus rigide. Toutes les étud-boutement sur la pression agissant sur la barricade étaient faites en un ou en deux dimensions (e.g. Doherty and Muir Wood, 2016; Shahsavari and Grabinsky, 2016; and Mkadmi et al., 2013). Fahey et al (2009) ont fait des comparaisons -boutement en déformation plane et axisymétrique permettant le développement des géométries qui -troi -boutement sur les contraintes agissant sur la barricade, les effets en déformation plane à deux dimensions sont suggérés.

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