ICGCM Papers:
Pillar and Mine Design III
 
 
International Practice in High Performance Underground Thick Coal Seam Extraction and Related Ground Control Challenges
32nd International Conference on Ground Control in Mining
International Practice in High Performance Underground Thick Coal Seam Extraction and Related Ground Control Challenges
by
Bruce K Hebblewhite, University of New South Wales, Sydney, Australia
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Author's Presentation PPT
[Conference] 32nd International Conference on Ground Control in Mining
[Price] Free  [Comments] 0
[Topical Area] Pillar and Mine Design III
[Author] Bruce K Hebblewhite, University of New South Wales, Sydney, Australia
[Abstract] 
Key Conclusions:
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It is clear that both of these methods are developing quickly - not only from an operational and equipment perspective, but also from the understanding of critical geotechnical criteria. There is an increasing role for both methods in thick seam environments, although the higher SPL faces will only be successful in the near to mid-term under bengin geotechnical environments. Regardless of the method, a thorough understanding of the critical geotechnical factors is a key to successful implementation of either method.
Key Findings:
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SPL operations are occurring in China with face heights up to 7m, but only under quite benign geotechnical conditions. SPL operations with face heights between 4.5m and 6m are more common, but also not without problems. Factors such as coal strength and structure are critical, together with regional stress and depth considerations. LTCC on the other hand can operate in conditions of weaker or more structured coal, and actually performs better under deeper and more highly stressed environments.
Objective of the Paper:
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This paper provides a review of a number of high performing thick seam mining operations around the world - both SPL and LTCC. The paper discusses the ground control issues faced by such operations, and some of the inherent geotechnical factors that can influence the mining method selection, design criteria and ultimate performance, from both an operational and safety perspective.
Problem Statement:
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Underground mining of coal seams with thicknesses in excess of 5m presents a number of both opportunities plus significant ground control challenges. Many mining methods have been adopted in different parts of the world, but with limited success in a lot of cases. In the past ten years, conventional longwall faces have struggled to achieve optimum productivity as well as resource recovery when cutting at heights above 5m, and in some cases even less. Ground control problems associated with face stability are one of the major challenges faced by these high reach single pass longwalls (SPL). However in the last two years, panels are being mined successfully with face heights up to 7m in parts of China. The other major mining system option is Longwall Top Coal Caving (LTCC). LTCC avoids the problems of high faces, but relies on good, predicatble and immediate caving of the top coal immediately behind the face in order to achieve optimum resource recovery. In both mining systems - SPL and LTCC - surface subsidence is a major consideration which must also be managed.