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|The importance of incorporating fundamental principles of rock material response and failure mechanics into a pillar strength design model has been demonstrated. To accurately assess pillar strength, a model should account not only for the characteristics of the coal, but also for those of the surrounding strata. The interactions between the pillar and the surrounding roof and floor dictate ultimate pillar strength. Confinement, or the lack thereof, provided by roof and floor frictional end-constraint is one of the most significant factors in the strength of very wide pillars. The best conditions for end-constraint occur with ideally strong roof and floor. In this paper, it will be shown that weak roof and floor may decrease the ultimate pillar strength by as much as 30% compared to ideal conditions. Field observations confirm this pillar strength reduction in the presence of weak roof and floor. Furthermore, rock partings within the coal have a variable effect on pillar strength, depending on the parting strength. A competent shale parting within the coal reduces the effective pillar height, thus increasing the ultimate pillar strength; a weak claystone parting slightly decreases the strength. Imposed load distribution also has a significant effect on pillar strength, such that asymmetric pillar loading, similar to that observed in pillars adjacent to high extraction mining, reduces the ultimate pillar strength below that of equivalent pillars subject to uniform load distributions.|
Additional chapters/articles from the SME-ICGCM book 16th International Conference on Ground Control in Mining (ICGCM)
|Longwall Mining-Through the Backfilled In-Panel Entries at C||Performance of Various Standing and Cribless Tailgate Suppor||Measurement of Effects of Interaction and Influence on Mine||Effects of Longwall Mining on Streamflow in the Pittsburgh S||Longwall Surface Subsidence Prediction Through Numerical Mod||Long-term Subsidence Over Longwall Chain Pillar Systems and||Subsidence Prediction Influence Assessment and Damage Contro||Formation of Face Headings Using Stress Relief at Asfordby M||Significant Weighting Events on the Longwalls in the Phalen||Full-face Pressure Monitoring in Medium-Weak Roof Condition||Research on the Interaction Between Roof Strata and Shield S||Roof Instability of Longwall Face at Ikeshima Colliery||Gob Canopy Roof Support for Difficult Natural Conditions||Yielding Cement Roof Supports for Longwall Mining||Management of the Dynamic Phenomena of Rock Pressure in Unde||Continuing Development of Innovative Cable Support Systems||Extending the Limits of Strata Bolting by the Use of Flexibl||Implementation and Evaluation of Roof Bolting in MICARE Mine||New Methods and Technologies of Roofbolting in Australia Coa||New Design Criteria for Roof Bolt Systems||Control Mechanism of a Tensioned Bolt System in the Laminate||A Study of the Performance of Glass Fibre Rock Reinforcement||A Method for the Selection of Rock Support Based on Bolt Loa||Strategies for the Application of Rockbolting Technology to||A Troubleshooting Guide for Roof Support Systems||A Statistical Overview of Retreat Mining of Coal Pillars in||Full-Scale Performance Evaluation of Mobile Roof Supports||Effect of the Interchamber Pi Yield on the Surface Strains i||Salt Pillar Design Equation||Case Study of Conditions Observed During the Removal of a Hi||Case Study of the Effect of Stratigraphic Location on Roof S||Ground Control and the Inundation of the Retsof Mine||Weatherability Test of Rocks for Underground Mines||Shear Strength Characteristics of Soft Rock Joints Based on||Comparison of Pillar Strengths Calculated Using Empirical Eq||Effects of In-seam and Near-seam Conditions and Asymmetric P||Ground Control Worker Safety During Extended Cut Mining||Analysis of Extensometer Data from a Room Widening Experimen||Airbag Support for Ground Control in Thin Seam Coal Mining||Development of a Statistical-Analytical Approach for Assessi||Ground Control Criteria for Coal Reserve Optimization in Mul||Calcium Aluminate Kiders in Hard Rock and Coal Mining||Simplified Pre-and Post-Processing Technique for Performing|