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|Roof bolting in the Pittsburgh Coalbed takes many forms today: coupled partially grouted bolts, fully grouted rebar, passive cable bolts, tensioned cable bolts, and torque tension rebar. The Federal No. 2 Mine of Peabody Energy has recently made a significant advance in longwall headgate primary roof support, with the change fiom an 8 ft long coupled partially grouted bolt to a 6 ft long torque tension system. The coupled partially grouted bolt consists of a 4 ft long 0.804 in diameter rolled deformation bar thread coupled to a smooth 718 in headed bar. The coupled partially grouted bolt is anchored into a 1 318 in borehole with 4 ft of high speed resin. The 718 in diameter smooth bar is tensioned by rotation into the treaded coupler, upon setting of the resin, compressing the immediate roof. The change was initially driven by occasional failure of the coupled partially grouted bolt at the threaded coupler, due to lateral movement caused by horizontal stress. A fully grouted % in diameter torque tension bolt, in a 1 in borehole, was proposed as a cost effective primary bolting for the high horizontal stress conditions. The upper 2 112 ft of the rebar is anchored in fast set, medium viscosity resin and the bottom 3 K ft is anchored in slow set, special low insertion force resin. The lower end of the rebar is threaded with a nut that permits the counter clockwise spinning of the bolt to mix the resin, at maximum rotational torque. Upon setting of the high speed top resin, the nut is spun clockwise to tighten the nut against a metal dome plate. The plate is forced against the roof to compress the immediate roof, A complete headgate entry has been successfully supported with the torque tension system. The mining of the adjacent longwall panel was completed in September 2004. The torque tension system provided a 25% savings over the previously employed coupled partially grouted bolt system.|
Additional chapters/articles from the SME-ICGCM book 24th International Conference on Ground Control in Mining (ICGCM) 24th
|Keynote Address at the 23rd International Conference on Grou||Analysis and Design of Rib Support (ADRS) a Rib Support Desi||Evaluation of the Impact of Standing Support on Ground Behav||Half a Career Trying to Understand Why the Roof Along the Lo||Forecasting Roof Falls with Monitoring Technologies - A Look||Analysis of Seismic Source Parameters of Roof Falls in Time||A System to Provide Early Warning on Impending Goaf||Outcomes of the Landmark Longwall Automation Project with Re||Application of Phenolic Foam in Longwall Mining||Multiple Seam Mining Interactions: Case Histories from the H||Analysis of Entry Stability Associated with Multi-seam Minin||Failure Mechanics of Multiple Seam Mining Interactions||Engineering Classification of Ultra-close Multiple Seam Roof||Definition of Ultra-close Multiple-seams and its Ground Pres||Depillaring and Roof Bolting Practices at Quinsam Coal Mine||Seam Structure - An Important Criterion for Coal Pillar Desi||Mitigating Longwall Subsidence Effects on a Large Industrial||Impacts of Longwall Mining on Hydrology, Soil Moisture, and||Basics on the Dimensioning and the Extraction of Shaft Safet||Modeling the Arc-effect of a Coal Mine Roof||Recent Advances in Numerical Simulation of Cutter Roof Failu||Test Method for Assessing Water Degradation Potential of Coa||Geotechnical Strata Characterisation Using Geophysical Boreh||A Method for Quantitative Void/Fracture Detection and Estima||Implication of Highly Anisotropic Horizontal Stresses on Ent||Ground Control of a Mine Stope in Weak Rocks Subjected to Hi||Analysis of Highwall Mining Stability - The Effect of Multip||Highwall Mining in a Multiple-seam, Western United States Se||The Slope Stability Assessment in the Wall Overlooking the S||Numerical Modeling as a Tool to Predict Pillar Condition and||Development and Testing of a New Roof Prop||Stability Mapping System||Using Foaming Grout to Stabilize a Ventilation Raise in Very||Roof Control and Roadway Support Design in the #9 Coal Seam,||Non-confirmation Mathematics for Wall Rock Classification fo||The Influence of the First Layer Thickness of Immediate Roof||Studies on Distribution Pattern of and Methane Migration Mec||Development of a New Roof Bolt Technology to Improve Gate- R||Improved Pull out Strength of Fully Grouted Roof Bolts throu||Experimental and Numerical Methodology Assessment of Load Tr||An Investigation into the Support Systems in South African C||Investigation of Fully Grouted Roof Bolts Installed Under In||Development of the Laboratory Short Encapsulation Pull Test||A Resin Quality Testing Procedure for Collieries||Determination of Load Transfer Characteristics of Gloved Res||Fully Grouted Torque Tension Bolts Successfully Support Pitt||Shear Bond Characteristics in Grouted Cable Bolts||Overcoring Techniques to Assess in Situ Corrosion of Galvani||Development of a Laboratory Facility for Testing Shear Perfo||Mechanical Response of Split-Set Rock Bolts in Squeezing Gro||Mechanisms of Rib Sloughing and Methods of Controlling Thick||Supporting Method of the Bolted Strata in Large Deformation||Assessment of Ground Conditions Near a Mine Portal Using Gro||Detection of Abandoned Mines and Air Passages/Burning Center||Detecting Abandoned Coal Mine Entries by High Resolution Ear|