Exploitation
Sruti Narwal; Debasis Deb; Sreenivasa Rao Islavath; Gopinath Samanta
Abstract
A novel underground mining method is proposed to extract friable chromite ore bodies in weak and weathered limonitic host rock below an open-pit mine. The conventional underground methods do not instil confidence since GSI (Geological Strength Index) of ore bodies and host rock lies below 35. Series ...
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A novel underground mining method is proposed to extract friable chromite ore bodies in weak and weathered limonitic host rock below an open-pit mine. The conventional underground methods do not instil confidence since GSI (Geological Strength Index) of ore bodies and host rock lies below 35. Series of dimensions of transverse stopes along the strike are suggested based on a detailed analysis of multiple mining and backfilling operations by simulating 36 three-dimensional numerical models. For each operation or sequence, a strength-based “Mining Sequence Factor (MSF)” is devised that helps quantifying its equivalent strength compared to in-situ conditions. This factor along with the average equivalent plastic strain (AEPS) developed on the pillars as obtained from numerical models is used to determine the safe operations with desired yearly production target. The paper provides an in-depth analysis of this method and suggests minimum pillar dimensions of 40 m, whether in-situ or backfilled. The paper, in addition, lays the design of underground drives and their support system as per NGI (Norwegian Geotechnical Institute) guidelines and 3D numerical studies, the performance of which is analysed considering distribution of stress and equivalent plastic strain.
Exploitation
Avula Rajashekar Yadav; Sreenivasa Rao Islavath; Srikanth Katkuri
Abstract
The installation gallery/set-up room of a longwall panel is driven for installation of the longwall face machineries to start the extraction of coal from the longwall panel. The width of the installation gallery is 8 to 9 m. This gallery needs to be stabilized till the face machineries to be deployed ...
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The installation gallery/set-up room of a longwall panel is driven for installation of the longwall face machineries to start the extraction of coal from the longwall panel. The width of the installation gallery is 8 to 9 m. This gallery needs to be stabilized till the face machineries to be deployed from the driving of the room as it required to stand more than 8 to 10 months and develop the high stress concentration, roof-to-floor convergence and yield zone in the roof and sides. Hence, in this study, a deep longwall mine of India is considered to analyze the behavior of set-up room. For this, a total of twelve 3D numerical models are developed and analyzed considering Mohr’s-Coulomb failure criterion. Three panels located at 417, 462, 528 m having three different widths (8, 10 and 12 m) of set-up rooms are examined. The width of the set-up room is taken based on the length of the shield support. The results in terms of vertical stress distribution, vertical displacement, roof-to-floor convergence, plastic strain and yield zone distribution are presented.
