The three-dimensional Distinct Element Method (program 3DEC) was applied to the stability of Jointed rock mass for a full scale test of a sublevel stoping mining method in Kiruna mine, Sweden. The computational model consists of 9 major faults and 256 blocks. The mining of primary rooms and pillars were simulated step by step. Complicated patterns of block movements with maximum displacement of about 100 mm was found in the modelling. Calculated deformations and stresses at a number of points in the model agree well with measured values from extensometers and stress monitoring cells. The modelling results were used to modify the layout and mining sequences of the stopes to avoid large ore losses and major failure. It was proven that the three-dimensional representation of discontinuous rock masses is essential for successful modelling of underground mining problems, especially with room-and-pillar structures.
La methode des elements distincts (programme 3DEC) a ete appliquee à la stabilite de massifs rocheux fractures pour un test à grande echelle d"une excavation minière à la mine de Kiruna en Suède. Le modèle est compose de 9 failles et de 256 blocks. L"excavation des chambres et pilliers primaires a ete simulee par increments. Des distributions complexes de movevement de blocks avec des deplacements de l"ordre de 100 mm ont ete predits par le modèle. Des deformations et contraintes calculees à plusieurs points par le modele sont en accord avec les va leurs mesurees à l"aide d"extensomètres et de cellules de mesure de contrainte. Les resultats du modèle ont ete utilises pour modifier l"arrangement et les sequences d"excavation afin d"eviter de larges pertes de minerais et des instabilites de grande taile. On montre que la representation à trois dimensions des massifs rocheux discontinus est essentielle dans les modèles de stabilite de mines souterraines, sutout pour les mines avec chambres et pilliers.
Mit der 3-dimensionalen Distinct Element Methode (3DEC-Programm) wurde fuer den Testausbruch mit einem bergmannischen Strossenabbauverfahren im Bergwerk Kiruna, Schweden. die Stabilitat eines gekluefteten Gebirgskörpers untersucht. Das Rechenmodell besteht aus 9 Hauptverwerfungszonen und 256 Blöcken. Komplizierte Blockbewegungen wurden gefunden, mit maximalen Veschiebungen von etwa 100 mm. Die berechneten Verformungen und Spannungen stimmten gut mit Extensometor und Spannungsmessungen im Gebirge ueberein. Mit Hilfe der Modellergebnisse wurden Anlage und Ausbruchfolge der Strossen modifiziert, um Erzverluste und Verbueche zu vermeiden. Es wurde gezeigt, dass eine 3-dimensionale Darstellung diskontinuierlicher Gebirgskörper notwendig ist, um bergmannische Abbaumethoden. wie vor allem den Kammerpfeilerbruchbau. erfolgreich in einem numerischen Modell erfassen zu können.
The traditional mining method used in Kiruna mine, LKAB, Sweden. is large scale sublevel caving with a typical drift distance of 16.5 m and slice height of 22m. The productivity of this method is limited by the pattern of discontinuous fan-drilling and ring-blasting cycles, and ore losses and waste dilution cannot be reduced substantially by increasing the mining scale alone. To improve the mining production and reduce the ore losses and waste dilution. a new large scale sublevel stoping method employing long blast holes of large diameter was tested at full Scale at the OSCAR test site (Fig.lal, so called the OSCAR project. An extensive in-situ monitoring network was installed in the test area to monitor the rock mass behaviour during test mining and the three-dimensional Distinct Element Method (OEM) was applied to simulate the test mining sequences and predict the stability conditions of stopes during the actual test mining. The numerical results were used to guide the design, of the mining sequences and dimensioning of the primary rooms. The computational model, validated against the results from in-situ monitoring, was then used to optimize the stope configuration and mining sequences (Jing and Stephansson, 1990).
