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|Successful longwall mining requires a stable tailgate entry. Gate entry performance is influenced by a number of geotechnical and design factors, including: - Pillar size and pillar loading; - Roof quality; - Floor quality; - Entry width; and, - Artificial support (primary and secondary). This paper describes a comprehensive, practical, design methodology, based on statistical analysis of a nationwide data base of longwall ground control experience. Geotechnical surveys were conducted at 44 U.S. longwall mines, and underground observations of site geology, entry conditions, and support design were recorded at each mine. The observations were combined with discussions with mine personnel to identify 69 longwall gate entry designs as satisfactory, unsatisfactory, or borderline. Only conventional longwall designs, in which the pillars are expected to carry the full abutment loads, were included in the data base. Designs which employed yield pillars only were excluded. The case histories were characterized using five descriptive parameters. Pillar design was described by the Analysis of Longwall Pillar Stability Factor (ALPS SF). A major new contribution is the Coal Mine Roof Rating (CMRR), a rock mass classification system that quantifies the structural competence of bolted mine roof. Other quantitative measures were developed for primary support, secondary support, and entry width. Multivariate statistical analyses indicated that in 84% of the case histories the tailgate performance could be correctly predicted using just ALPS and the CMRR. Most of the misclassified cases fell within a very narrow borderline region. The analyses also confirmed that primary support and gate entry width are essential elements in successful gate entry design. The relative importance of the floor and of secondary support could not be determined from the data. Based on these results, a simple equation was developed to guide the design of longwall pillars and gate entries: ALPS SF,, = 1.76 - 0.014 CMRR Where: ALPS SF, = ALPS SF suggested for design. Guidelines for entry width and primary support density, as related to the CMRR, are also provided.|
Additional chapters/articles from the SME-ICGCM book Proceedings of 12th International Conference on Ground Control in Mining
|Bolting Practice In Longwall Gateroads At The Miike Colliery||Cable Supports For Improved Longwall Gateroad Stability||Comparisons Of Active Versus Passive Bolts In A Bedded Mine||Flexibolt Flexible Roof Bolts: A New Concept For Strata Cont||The Design And Application Of Hercules Cribs For Underground||Cyprus Shoshone Tailgate Roof Control: Case Study||Engineering Methods For The Design And Employment Of Wood Cr||The Use Of Foamed Cement Cribs At American Electric Power Fu||A Comparison Of Support Reactions To Retreat Longwall Front||Entry Design For Optimum Stability In A Multi-Seam Environme||Gate Entry Design For Longwalls Using The Coal Mine Roof Rat||A Test Of Predictive Numerical Models To Simulate Entry Desi||The Coal Mine Roof Rating (CMRR) A Practical Rock Mass Class||Comparative Analysis Of Longwall Gateroad Designs In Four De||Further Improvements In The Roof Beam Tilt Method Of Gateroa||Application Of A Static And Geophysical Monitoring System Fo||Flexible Support Design For Gateroads Of Retreating Longwall||Longwall Support Monitoring||Case Studies Using Mine-Wide Monitoring Systems For Geotechn||An Application Of Tree Classification Method In Analysis Of||Image Analysis Development And Application To Fracture Patte||Mathematical Modeling Of Strong Roof Beds In Longwall Mining||Load Deformation Behavior Of Simulated Longwall Gob Material||Monitoring Of The Interaction Effects Over A Longwall Panel||Design, Monitoring And Evaluation Of A Pre-Driven Longwall R||Ground Control And Safety Considerations During Longwall Rec||Utilization Of Polymer Grid Structures In Shield Recovery Op||The Impact Of Variability In Coal Strength On Mine Planning||Underground Application Of Optimization||Modern Geotechnical Exploration And Mine Design||A New Method For Longwall Pillar Design||A Rock Mass Strength Concept For Coal Seams||Techniques To Increase Yield Pillar Residual Strength||Application Of Seismic Tomography For Assessing Yield Pillar||Structure, Strength And Relaxation Of Interbuden For Input I||Rock Compaction Caused By Dewatering In Poorly- Consolidated||Correlation Between The Effect Of Confining Pressure On Comp||Characterization Of Structural Integrity And Stress State Vi||Rock Mechanics Property Data Bank For Coal Measure Strata||Failure Modes Of Mine Tunnels In Stratified Rock Structures||Determination Of Plate Size Effect On Ultimate Bearing Capac||Development And Evaluation Of A Floor-Bearing Capacity Test||Investigation Of Blast Damage And Underground Stability||Development Of A Slope Stability Program For Improved Quarry||Material Instability Hazards In Mine Processing Operations||Mine Design Considerations For Surface Subsidence Control||Surface Fracture Development From Mine Subsidence In Eastern||An Integrated Approach To Subsidence Modelling And Predictio||Effect Of High-Extraction Coal Mining On Surface And Ground||Economic Evaluation Of Subsidence Damage Mitigation Techniqu|