A numerical modelling study to assess the stress distribution in two nearby backfilled openings created in sequence

N. Falaknaz, M. Aubertin, L. Li

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Mining Geotechnics

ABSTRACT: al modelling study to assess the stress distribution in two nearby backfilled openings created in sequence Falaknaz, N., Aubertin, M., Li, L. Research Institute on Mines and the Environment, RIME UQAT-Polytechnique, École Polytechnique de Montréal, QC, Canada ABSTRACT Backfilling of underground mine stopes is used to provide a safe work place. The interaction between the backfill and surrounding rock mass has to be evaluated for a secure application. The stress distribution in backfilled stopes is influenced by various factors including the excavation of adjacent openings. Recent simulations results have shown some of the complex interactions that can develop between the backfill and rock mass in the case of neighboring stopes. In this article, the authors present additional numerical simulation results to illustrate the response of two nearby stopes created and backfilled in sequence, considering the influence of other factors, i.e. pillar width, properties of the backfill and rock mass, and natural stress state. Key results, shown in terms of the stresses and strains in the backfill and displacements of the rock walls, are analyzed and discussed. RÉSUMÉ Le remblayage des chantiers miniers souterrains permet de créer un espace de travail remblai et le massif rocheux doit être évalué pour une application sûre. La distribution des contraintes dans les chantiers remblayés est influencée simulations numériques récentes ont illustré certaines des interactions complexes qui peuvent se développer entre le remblai et le massif dans le cas de chantiers voisins. Dans cet article, les auteurs montrent des résultats de simulations additionnelles sur la réponse présente ici les résultats en termes des contraintes et des déformations dans le remblai et des déplacements aux parois, avec une analyse et une discussion. 1 INTRODUCTION Underground mining is sometimes defined as the removal of economically viable volumes of rock, which creates underground openings that can be stabilized by adding backfills. In addition to improve wall stability around stopes, backfilling can also reduce ore dilution and the impact of mine wastes disposal on the surface (e.g. Hassani and Archibald, 1998). A good understanding of the mechanical behavior of the backfill and its interaction with the surrounding rock mass is a key step to assess the geomechanical response of backfilled stopes and related ground stability issues. It is well known that the different behavior of the fill materials and rock mass, in terms of shear strength and stiffness, can lead to a transfer of the stresses from the backfill to the surrounding rock, a phenomenon known as arching (e.g. Knutsson, 1981; Hustrulid et al., 1989; Handy and Spangler, 2007). Arching effects in backfilled stopes can be evaluated using analytical solutions, which are often based on the Marston (1930) approach initially developed for backfilled trenches (e.g. Aubertin et al., 2003; Li et al., 2005; Li and Aubertin, 2008; Pirapakaran and Sivakugan, 2007; Ting et al., 2011). Numerical simulations have also been widely used to assess the response of isolated (single) backfilled stopes, considering the effect of various factors such as fill properties, stope geometry, filling rate and water pressure (e.g. Li et al., 2003, 2007, 2009a, 2009b, 2009c; Veenstra, 2013; El Mkadmi et al., 2014). The influence of excavating adjacent stopes on the backfill response has only been addressed recently by Falaknaz et al. (2013), who also considered the influence of a few variables such as internal friction angle and cohesion of the fills and stope width. In this paper, the interaction between the backfill and rock mass around two adjacent vertical stopes, created one after the other, is investigated using FLAC (Itasca, 2002). The simulations include an evaluation of various factors that may influence the stress distribution, namely stope depth, pillar width, and rock mass properties. The results shown here illustrate specifically how the excavation and backfilling of a second stope may affect the stresses within the first backfilled opening. 2 BASIC CHARACTERISTICS OF THE MODEL AND OF BACKFILL FLAC 2D (Itasca, 2002) is commonly used to analyze the stress state in backfilled stopes. This two-dimensional finite difference program can be used for modelling complex problems, with different constitutive models, material properties, and boundary conditions.

RÉSUMÉ: merical modelling study to assess the stress distribution in two nearby backfilled openings created in sequence Falaknaz, N., Aubertin, M., Li, L. Research Institute on Mines and the Environment, RIME UQAT-Polytechnique, École Polytechnique de Montréal, QC, Canada ABSTRACT Backfilling of underground mine stopes is used to provide a safe work place. The interaction between the backfill and surrounding rock mass has to be evaluated for a secure application. The stress distribution in backfilled stopes is influenced by various factors including the excavation of adjacent openings. Recent simulations results have shown some of the complex interactions that can develop between the backfill and rock mass in the case of neighboring stopes. In this article, the authors present additional numerical simulation results to illustrate the response of two nearby stopes created and backfilled in sequence, considering the influence of other factors, i.e. pillar width, properties of the backfill and rock mass, and natural stress state. Key results, shown in terms of the stresses and strains in the backfill and displacements of the rock walls, are analyzed and discussed. RÉSUMÉ Le remblayage des chantiers miniers souterrains permet de créer un espace de travail

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N. Falaknaz; M. Aubertin; L. Li (2014) A numerical modelling study to assess the stress distribution in two nearby backfilled openings created in sequence in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper138,author = N. Falaknaz; M. Aubertin; L. Li,title = A numerical modelling study to assess the stress distribution in two nearby backfilled openings created in sequence,year = 2014}