A Study of Influence of Adjacent Goaf for Safe Extraction of Coal at Deeper Depth Using Continuous Miner-Based Mass Production Technology

Abstract

Depillaring a panel surrounded by old goaved-out area experiences strata mechanics challenges in terms of instability of barrier pillars and production pillars due to re-distribution of the abutment load. The study focused on panel 89LW of Churcha RO Underground Mine, surrounded by goaf in three sides, and being extracted using continuous miner (CM) based mass production technology. A comprehensive numerical modelling, field experimentations and strata monitoring study is conducted for safe extraction. Numerical modelling results revealed that the barrier pillar bears the majority of the abutment load from the adjacent goaved-out panels. It is observed that the maximum absolute stress is developed in case of unsettled goaf compared to the settled goaf. Drill yield experiment confirmed that the panel is not prone to coal bump. The support system is efficiently stabilizing the immediate roof as no strata movement observed through dual height tell-tale (DHTT). Maximum vertical induced stress of 98.59 kg/cm2 over snook when the pillar was extracted. Around 50% of the panel is successfully extracted till date and the field and numerical modelling studies revealed that no impact of old settled goaf noticed. This study will be helpful for mining industry during CM-based mechanised depillaring under similar geo-mining conditions.