Critical evaluation and qualitative comparison of two mining methods for a sustainable underground extraction of Marignac

Anton Isola

Research output: ThesisMaster's Thesis


In order to realize the underground mining of the deposit Marignac in the OMYA mine St. Beat, the first step is to evaluate suitable mining methods based on stability and costs, which is the objective of this master thesis. Based on preliminary studies, two mining methods have been selected for closer examination. This is, on the one hand, a sublevel open stoping method, as already applied in existing mining areas of St. Beat, and, on the other hand, the so-called raise mining method. Compared to sublevel open stoping, raise mining on a mechanized large scale represents a relatively new mining method, which has only been used in two underground operations so far and experience is accordingly limited. Furthermore, there is limited experience related to the strength and behavior of the pillar compound system, which is formed by raise mining stopes with a circular or elliptical cross-section, available. The stability of both selected mining methods is analyzed by means of numerical simulations and both mining method are compared qualitatively. For this purpose, individual excavations and individual sublevel open stoping as well as raise mining panels are examined first. Subsequently, a sublevel open stoping layout and a raise mining layout with roughly the same recovery rate are investigated in rock engineering conditions found in Marignac. The qualitative comparison of the two mining methods, via the results of the numerical simulations, shows that raise mining is more favorable in terms of stability for underground extraction of Marignac than sublevel open stoping with the same recovery rate. Important therefore is particularly the special shape of the pillar compound system. This special shape of the raise mining pillar system creates a greater and mostly three-dimensional confinement compared to the pillar system of sublevel open stoping, which results in a greater strength of the pillar compound system. The narrow sections of the raise mining pillar system represent their weakest points, but even they have a higher confinement than the pillars in the sublevel open stoping system. The influence of the dominant discontinuity system in Marignac is also conceptually discussed. Intersections of discontinuities with stope walls can result in critical blocks that can further lead to structural controlled failure. Due to the great height of the raise mining stopes critical blocks occur in the raise mining pillar system more frequently in vertical direction, but on shorter horizontal lengths. However, the higher confinement in the raise mining pillar system has a positive effect on the restraining forces acting on the critical blocks, which counteracts structural control failure. Beside the stability, a productivity analysis of the two mining methods has been conducted. It has been shown that productivity, measured in tonnage mined per man-hour, is higher for the raise mining method than for sublevel open stoping. This result leads to the hypothesis that raise mining is also preferable over sublevel open stoping in terms of costs. In order to prove this hypothesis, the current specific costs of the individual mining activities in St. Beat need to be considered and such analysis shall be done in future. The results of this thesis clearly favor the application of raise-mining in Marignac over the application of sublevel open stoping. However, there are open points regarding raise mining in Marignac, which comprise particularly the stability of raise mining stopes and the pillar compound system. Corresponding investigations are recommended. These investigations should be carried out with detailed information regarding the geological and geotechnical conditions in Marignac.
Translated title of the contributionKritische Bewertung und qualitativer Vergleich von zwei Abbaumethoden für eine nachhaltige Untertagegewinnung von Marignac
Original languageEnglish
Awarding Institution
  • Montanuniversität
  • Sifferlinger, Nikolaus August, Supervisor (internal)
  • Ladinig, Tobias, Co-Supervisor (internal)
Award date16 Dec 2022
Publication statusPublished - 2022

Bibliographical note

embargoed until 04-11-2027


  • Qualitative comparison
  • Raise mining
  • sublevel open stoping
  • stability investigations
  • numerical simulations

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