Analysis of Strata Behaviour during Final Extractions in Underground Coal Mining under Difficult Caving Characteristic of Roof Condition
Authors
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National Institute of Technology, Raipur, 492 010 ,IN
S. K. Jena -
Visvesvaraya National Institute of Technology, Nagpur, 440 010 ,INR. D. Lokhande
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National Institute of Technology, Raipur, 492 010 ,INM. Pradhan
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South Eastern Coalfields Limited, Bilaspur, 495 006 ,INN. Kumar
Keywords:
Underground Coal Mining, Strata Pressure, Dynamic Loading Effect and Strata Movement.Abstract
During bord and pillar depillaring with caving in underground coal mining, strata pressure in the goaf roof keeps on mounting with increasing span of goaf. The strata pressure may propagate into the workings in the form of dynamic loading effects carrying potency of premature collapses. The loading effect can be revealed at goaf edges and influenced zone of workings by strata control instrumentation monitoring for convergence, load, local induced stress etc. Such strata pressure reaches to a peak and is termed as ultimate induced stress, before main fall occurs in the goaf. When overlying rock formations are strong enough, it may lead to caving constraints and propagation of strata movement into workings may occur in a larger way, requiring proper control measures. Principal control measures include, adequate support provisioning in the vulnerable places including at goaf edges, proper methodology of extraction, artificial induced failure of goaf roof etc., which are possible, only when the peak strata movement is predicted in advance of roof fall. The objective of the study is to analyse the strata behaviour during peak loading hours and prediction of ultimate strata movement during extraction under strong roof conditions, using the already developed model of the author, ‘Roof Fall Warning Index’.
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