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|In spite of the extensive research and accumulated experience from mining operations, an appropriate pillar design remains an open issue. Due to the shrinking reserve base, present mining operations move to more challenging conditions. There are usually thinner seams and geologic conditions are often unfavorable. For instance, mine roof and floor are weak or deteriorate rapidly when exposed to moisture fluctuations in mine atmosphere. It is common that pillars of current operations are more- squat than several decades ago when the bulk of pillar research have been carried out in thicker seams. The methods of pillars calculations were developed regionally (in particular countries) to suit design needs for the most important seams, from which the majority of coal production was coming (e.g. Pittsburg or Pond Creek seams in the eastern of US). Most of the pillar formulae use similar approach by assigning weights (using constants) to the influence of coal (seam) strength and pillar widthheight ratio on its final strength. That mechanistic approach has sound theoretical base and good data supporting its validity. However, what seems to be missing is a qualification system of the mine conditions, which are outside of the data base or do not comply with the theoretical model applied in pillar strength formulae. This paper attempts to address that issue in two major categories, first when only a drill core data are available, and second during the mine development observations can be made directly on a coal seam. The composition of a coal seam is also addressed, (which often changes rapidly across the reserve), and discussed its influence on pillar's structural performance. In summary a set of practical design rules is presented.|
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|