Numerical modeling of longwall top coal caving method at thar coalfield

NM Shahani, Z Wan, X Zheng, L Guichen, C Liu, F I Siddiqui, G Bin


Thar Coalfield in Pakistan is the largest reserve of lignite coal in the country, which is outlined by thick coal seams. The preferred mining method for these thick coal seams is the Longwall Top Coal Caving (LTCC). The connection of both the top coal caving and its compactness are still rare; therefore, the capability of top coal caving mechanism is the most significant factor in LTCC that must be adequately explained and examined. Moreover, in order to achieve the ideal coal production, a comprehensive modeling of deformation and induced stress is mandatory. In this study, a 12 m thick coal seam with cutting to caving height ratios like 1:2 and 1:3 has been modelled, and the mechanism of longwall top coal caving demonstrated and front abutment vertical stress distribution in front of face line values were computed with the help of UDEC at Block-IX, Thar Coalfield. The results reveal that a thick layer of top coal can be progressively caved behind the face at the ratio 1:3 instead of 1:2 (which explained the incompetent caving progress of top coal). Similarly, the maximum vertical abutment stress of 20 MPa was observed at 6m in front of the face when cutting to caving height ratio was 1:2 and at 3m in front of face with 1:3 (which is comparatively capable for the face advancement), respectively. Therefore, this numerical modeling study proposes the reasonable height of top coal caving at cutting to caving height ratio 1:3 for the efficient production of thick coal seams at Thar Coalfield.

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