Roof Support System in Underground and Monitoring
Field investigations were carried out over a two-year period at NCPH Colliery of S.E.C.L; R-6 Mine site for evaluation of strata behavior during extraction of coal in a 6.5 m thick seam by continuous miner at a depth of 106 m. Numerical and empirical models were also used for modification of existing support system leading to formulation of guidelines for the Strata Management. For the geomining conditions of R-6 mine, maximum of 16 mm roof convergence was observed during widening of galleries. Conventional support system of cement grouted roof bolts of 1.5 m length, 22 mm diameter at a spacing of 1.5 m between rows and 4 bolts in a row. With this conventional support system, widening of galleries up to 6 m has shown no considerable convergence but greater than 6 m wide galleries has resulted in the formation of undulated roof and floor conditions. Based on field observations including convergence of development and depillaring galleries and numerical modeling studies, the support system was modified with resin bolting so as to provide safer working conditions. The modified support system has 1.8 m long resin bolt for split galleries, 2.4 m long resin bolts for original gallery and point-anchored rebar at 1.5 m center-to-center spacing for the roof conditions of NCPH mine. Based on Numerical modeling results, the bolting was found efficient at a distance of 0.6 m from the side of the pillar and 1.5 m distance from the adjacent bolt. Although this work is based on studies carried out for the geomining conditions of the NCPH Colliery; R-6 Mine, it is believed that the findings can be applied to other shallow depth coal mines in similar geological conditions. A significant improvement in safety, productivity, and economy was observed at the NCPH Colliery R-6 Mine by adopting many of the recommendations, and strata management guidelines developed through this work.