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|Coal strata strength is included as a vague term in most of the pillar design formulas, either as a questionable fraction of the intact coal strength or a size-dependent relationship for scaling down a laboratory value to the in situ strength. In order to introduce a coal mass strength criterion which would be compatible with current design trends, the Rock Mass Rating (RMR) system was revised to incorporate factors governing coal seam behavior under load. A number of adjustment factors have been proposed but, the most significant change, is the introduction of a parameter representing the heterogeneity of the seam. When developing a rock mass strength criterion, it is necessary to find the constants of appropriate intact rock strength criteria and to establish a correlation to scale down these constants as a function of the RMR. For four intact rock strength criteria, the constants for coal were found using the Nelder-Mead method. To correlate the constants of the strength criteria with the coal seam quality values (RMR), a procedure was developed based on finite element modeling of in situ large scale tests for which the RMR was known. A new coal strata strength criterion is proposed, in a principal stress formulation, for modeling coal pillar behavior when the stress field in a pillar is known. A linear relationship is also given, to be used when empirical pillar strength formulas are used to design pillars. The proposed criteria have been evaluated in a case study.|
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|