Study on Rock Load Variation Considering Weatherability in Bord and Pillar Method of Underground Coal Extraction
Keywords:
Rock loading effect, Weathering, Bord and pillar method, Slake durability index, CMRI-ISM RMRAbstract
In India, bord and pillar is the most commonly used method in the extraction of coal which contributes approximately 98% production from underground. Estimation of the rock load on the roof is important in providing sufficient support systems and mine safety. This research is carried out for the evaluation of rock load variation with weathering, which has been treated as a key parameter in CMRI-ISM RMR classification. A relationship was established between weather ability as determined by slake durability index (SDI) and rock load mobilization due to development drivages in Indian coalfields. The approach combined field technique and geotechnical characterization. Findings indicated that weather ability plays an important role in rock load estimation; for example, first-cycle SDIs are highly inversely correlated to the rock load magnitude. Strong coefficients of determination (R² > 0.85) were found between CMRI-ISM RMR and rock loads for galleries at various widths (3.6-4.8 m). Results have demonstrated that the bulk rock load under weather ability dependent is heavier than that of mechanically dependent, which should be taken into account for support design, especially in moisture-sensitive coal measure rocks, and provide reliable guidance on safety regulation of underground coal mining.
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