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|Despite more than half a century of experience with roof bolting, no design method has received wide acceptance. To begin to improve this situation, National Institute for Occupational Safety and Health (NIOSH) conducted a statistical study of roof bolt performance at a number of mines throughout the U.S. Case histories were collected from 37 mines with a variety of roof bolt types and patterns in a wide range of geologic environments. Performance was measured in terms of the number of roof falls that occurred per 10,000 ft of drivage. The study found that roof falls are rare when the roof is strong and the stress is low, even with light roof bolting patterns. The focus of this paper is on the more difficult conditions, where the roof is weaker and/or the stress is higher. Analysis of the results led to guidelines that can be used to make preliminary estimates of the required bolt length, capacity, and pattern. The guidelines are based on the depth of cover (which correlates with stress) and the roof quality (measured by the Coal Mine Roof Rating (CMRR), and the intersection span. Another contribution is a formula for estimating the horizontal stress level in the eastern U.S. coalfields as a function of the depth of cover. The design guidelines are currently being implemented into a computer program called Analysis of Roof Bolt Systems (ARBS).|
Additional chapters/articles from the SME-ICGCM book Proceedings 20th International Conference On Ground Control In Mining
|Hydraulic Fracturing Of Sandstone And Longwall Roof Control||Status Of Longwall Research In CSIRO||Longwall Moves At Twentymile Recovery Mesh System||Risk Assessment Of Geotechnical Factors Associated With Unde||Load And Deflection Response Of Ventilation Stoppings To Lon||The Stress And Failure Paths Followed By Coal Mine Roofs Dur||Simulated Materials Modeling And Analysis Of The Overburden||Sizing Of Final Stumps For Safer Pillar Extraction||Evaluation Of Mobile Roof Support Technologies||FDM Prediction Of A Yield Pillar Performance In Conjunction||Extraction Ratio In Thin Seams Assuring No Surface Subsidenc||Improving Roof Control At A South African Coal Mine||In-Situ Investigation Into The Causes Of Falls Of Roof In So||Failure Characteristics Of Roof Falls At An Underground Ston||Determination Of Limitation Of Roof Layer Separation (LRLS)||The Integration Of Geology And Engineering In Ground Control||Worldwide Implementation Of Continuous Miner System - Integr||Effect Of Face Advance Rates On The Characteristics Of Subsi||The Response Of A High Order Stream To Shallow Cover Longwal||SDPS For Windows: An Integrated Approach To Ground Deformati||Development Of A Remote Reading Dual-Height Telltale System||Enhanced Surface Control For Roof And Rib Support||Long Term Stability Of Mine Workings In Soft Floor Environme||Visualization Of Geostructure By Mechanical Data Logging Of||A Step Towards Understanding The Behaviour Of Wider Roadways||Research And Application Of Combined Reinforcement System||Estimation Of In-Situ Stress At Ikeshima Colliery Using AE A||Typical Complete Stress-Strain Curves Of Coal||Analysis Of Roof Bolt Systems||Effects Of Bedding Plane Sliding And Separation And Tensione||Systems Used In Coal Mining Development In Long Tendon Reinf||Determination And IT-Supported Evaluation Of Rock Mechanical||Tensioned Cable Bolts As Primary Support: Update||Determination Of Basis For The Double Use Of Rectangular Roc||Cost Preventive System To Control Unstable Roof In Main Line||Injection Techniques for Cost-effective Stabilization of Bri||An Analysis of Rock Failure Around a Deep Longwall Using Mic||Numerical Simulation on Microseismicity Due to Mining at One||Investigation of Seismicity Near Appin, NSW, and its Associa||Effects of Bolt Spacing, Bolt Length, and Roof Span on Bolt||Evaluation of Instrumented Cable and Rebar Bolts as Ground S||Application of the Coal Mining Roof Rating System in South A||Roof Instability Rating (RIR) System and Its Application at||Updating the NlOSH Support Technology Optimization Program (||Mistakes, Misconceptions, and Key Points Regarding Secondary||Non-Destructive Testing on Fully Grouted Rockbolts||Visual Recognition of the Load of Roof-Bolts by an Indicator||A New Rockbolt Axial Load Measuring Device||A New Approach to the Integrity Testing of Ground Anchorages||A Lineament Analysis Case Study of the Fola Coal Co., LLC. N||Analyses of Valley Fill Slope Stability - Three Case Studies||Modeling of Joint and Fracture Distributions in Rock Mass Be|