ICGCM Papers:
Roof Support Design and Evaluation
 
 
Roof Bolting in Low Seam Mining with Thick "Stack Rock" Roof under High Horizontal Stress
29th International Conference on Ground Control in Mining
Roof Bolting in Low Seam Mining with Thick "Stack Rock" Roof under High Horizontal Stress
by
Peter Zhang, Technical Services, Maxxim Shared Services, LLC An Affiliate of Alpha Natural Resources, Inc., Waynesburg, United StatesScott Wade, Technical Services, Maxxim Shared Services, LLC An Affiliate of Alpha Natural Resources, Inc., Waynesburg, United StatesEd Zeglen, Technical Services, Maxxim Shared Services, LLC An Affiliate of Alpha Natural Resources, Inc., Waynesburg, United StatesScott Peterson, Technical Services, Maxxim Shared Services, LLC An Affiliate of Alpha Natural Resources, Inc., Waynesburg, United StatesRod Lawrence, Technical Services, Maxxim Shared Services, LLC An Affiliate of Alpha Natural Resources, Inc., Waynesburg, United StatesMike Mishra, Technical Services, Maxxim Shared Services, LLC An Affiliate of Alpha Natural Resources, Inc., Waynesburg, United StatesRick SmithGary DeemerRobert Bottegal, Amfire Mining Company, LLC, Latrobe, United States
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[Conference] 29th International Conference on Ground Control in Mining
[Price] Free  [Comments] 0
[Topical Area] Roof Support Design and Evaluation
[Author] Peter Zhang, Technical Services, Maxxim Shared Services, LLC An Affiliate of Alpha Natural Resources, Inc., Waynesburg, United StatesScott Wade, Technical Services, Maxxim Shared Services, LLC An Affiliate of Alpha Natural Resources, Inc., Waynesburg, United StatesEd Zeglen, Technical Services, Maxxim Shared Services, LLC An Affiliate of Alpha Natural Resources, Inc., Waynesburg, United StatesScott Peterson, Technical Services, Maxxim Shared Services, LLC An Affiliate of Alpha Natural Resources, Inc., Waynesburg, United StatesRod Lawrence, Technical Services, Maxxim Shared Services, LLC An Affiliate of Alpha Natural Resources, Inc., Waynesburg, United StatesMike Mishra, Technical Services, Maxxim Shared Services, LLC An Affiliate of Alpha Natural Resources, Inc., Waynesburg, United StatesRick SmithGary DeemerRobert Bottegal, Amfire Mining Company, LLC, Latrobe, United States
[Abstract] 

Thinly-laminated sandyshale, so called “stack rock”, is always difficult to support in underground coal mines.  With thin laminations of 0.1-2 in and weak bonding between laminations, the roof is much weaker under horizontal stress than under vertical load.  Buckling of thin laminations and cutters are common signs of initial failure for this type of roof.  When a roof fall occurs, it is mostly above the primary bolted horizon with a flat top and steep breaking angle above the pillar ribs.  As sandyshale is so brittle, roof falls mostly develop without significant roof sagging.  With thick laminated sandyshale, it is difficult to build a strong beam with short primary bolts.  Longer bolts than the mining height, straps, and supplementary bolts are required.  Since longer primary bolts are difficult to implement in low seam mining, supplementary bolting is important to maintain overall roof stability.  The bolting plan should also be chosen based on the geologic hazard map which shows the distribution and thickness of laminated sandyshale, and the transition areas.         

The paper is based on a case in a low seam mine which has laminated sandyshale roof with joints and under high horizontal stress. Roof falls occurred with different bolting system and mine orientation in the past.  An optimal roof bolting plan is sought through geologic mapping, roof scoping, theoretical modeling and analysis, and testing of different bolting plans.  The paper presents the roof fall distribution and characteristics in the mine, correlates the falls with geologic conditions, analyzes the critical factors in controlling the roof stability, evaluates the performance of different tested bolting plans, and provides an effective solution to supporting the troublesome roof.