Stability assessment of post pillars in cut-and-fill stoping method at trepça underground mine

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Tezin Türü: Doktora

Tezin Yürütüldüğü Kurum: Eskişehir Osmangazi Üniversitesi, Fen Bilimleri Enstitüsü, Maden Mühendisliği, Türkiye

Tezin Onay Tarihi: 2019

Tezin Dili: İngilizce

Öğrenci: GZIM IBISHI

Danışman: Mahmut Yavuz

Özet:

Stability assessment of deep underground excavations in hard rock mines is one of the most important issues in rock engineering design. Stability issues correlated with mining at great depth below the ground surface has become a challenge for researchers and engineers due to presence of high in situ stress state and complexity of geological rock mass conditions. Deep underground excavations (e.g. stopes) are more likely to suffer from ground falls since disturbed rock mass induce stresses which are usually high enough to exceed the strength of the rock mass causing failures which might be manifested in the form of rock fall and spalling. Hence, rock falling and/or spalling might affect the overall safety in production stopes causing of fatalities, damage of underground equipment and machinery, and cause delays to mining operations. Within the scope of this thesis, the maximum mine excavation height and minimum required dimensions of post-pillar have been investigated varying mine excavation depth based on 3D numerical modeling and analysis. The support of overhand cut-and-fill stoping method is mainly provided by post-pillars. Post-pillars have great influence on overall stope stability in thick ore bodies. This research focuses on post-pillar stability assessment under static loading conditions to understand pillar behavior with respect to mine excavation height and depth. Numerical modeling of the whole mining method is simulated using FLAC3D code, investigating extent of failure zones and distribution of maximum principal stresses around excavated stopes and in post-pillars. Design of post-pillars should be done in such a way that failure does not take place at the first excavation stage. A new assessment index i.e. Pillar Yield Ratio (PYR) and Pillar Stability Graph (PSG) investigating stability of post-pillars has been developed. Here, the objective is to determine a border line between stable, potentially unstable, and failed state of post-pillars at a specific mine site (e.g. Trepça Underground Mine).