Stability Assessment of Underground Structures During Extraction of Thick Seam Using Continuous Miner: A Case Study

Abstract

The application of continuous miner technology in de-veloped thick coal seams presents considerable stability chal-lenges, particularly where the immediate roof is weak and strati-fied. This study was conducted to assess the stability of heightened coal pillars and associated underground structures during continu-ous miner-based mechanised depillaring in Panel C-2A of GDK-11 Incline Mine, SCCL, with the objective of ensuring safe and efficient coal extraction. A comprehensive approach combining numerical modelling, empirical analysis and field monitoring was adopted. The stability of heightened pillars was evaluated through the combined consideration of width-to-height ratio and factor of safety. Rock load height analysis using numerical modelling indi-cated that junction areas require reinforcement with a support sys-tem consisting of 2.4 m roof bolts and 5 m flexi bolts. The stability of various underground structures including pillars, fenders, and rib/snook was also analysed through numerical modelling and found to be satisfactory. Extensive strata monitoring was carried out using dual-height tell tales, rotary tell tales, auto warning tell tales, extensometers and stress meters. Instruments installed at dif-ferent locations performed effectively and provided timely early warnings before roof falls. Using this integrated approach, coal seams up to 6 m thickness were successfully extracted with con-tinuous miner technology. The study demonstrates that careful pil-lar heightening, supported by well designed artificial supports and systematic strata monitoring, can enable safe and efficient extrac-tion of thick coal seams under challenging geo-mining conditions.