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|Coal mass strength properties must be estimated to obtain realistic estimates of coal pillar strength. The limitations of existing techniques for approximating these properties are discussed. The coal mass is anisotropic. The Hoek and Brown approach to rock mass property estimation is modified to allow for this. This approach requires the Rock Mass Rating (RMR) for the strata. In the normal case where bedding is sub-horizontal, these major planes of weakness have little effect on the strength of pillars. As a result of this the RMR must be measured parallel to bedding. This means that a significantly higher rating than that usually obtained for coal is observed. The use of mass strength property estimates in extant empirical relationships is outlined. At high width to height ratios, an acceleration in the rate of increase in pillar strength with increasing width to height ratio has been observed. The empirical relationship developed by Salamon (the so called squat pillar formula) takes account of this. This relationship was found to have significant limitations with respect to its universal application. Modifications arc made to Bieniawski's empirical formula to extend its use to large width to height ratio (squat) pillars. This new squat pillar formula has none of the disadvantages associated with Salamon's relationship. Strain softening was incorporated into non-linear finite difference numerical modelling to estimate pillar strengths. The technique outlined above is used to obtain peak coal mass properties. Modelled pillar strength was found to be sensitive to both peak and post peak mass strength properties. Post peak properties were found to be difficult to obtain and required some back analysis. Modelling results were used to estimate both the strength of squat pillars and parameters for use in a now squat pillar empirical strength relationship.|
Additional chapters/articles from the SME-ICGCM book 11th International Conference on Ground Control in Mining Proceedings (ICGCM) 11th
|Assessment Of Applicability Of Strength Criteria For Rock An||A Method For Establishing Site Specific Coal Pillar Design G||Strata Mechanics Of Pillar Extraction Goaf Edges||Rock Mass Classification As An Aid To Estimating The Strengt||A Study On Stress Distribution And Reasonable Size Of Coal P||Evaluating Coal Pillar Mechanics Through Field Measurements||Critical Appraisal Of Pillar Design As Required By Coal Mine||Sidewall Fracturing In Coal Room And Pillar And Pillar Extra||Design Of Yield Pillars In The Southern Coal Field Of New So||Pillar Design In Bump-Prone Deep Western U.S. Coal Mines||Elasto-Plastic Finite Element Structural Stability Analysis||Scale Model Studies To Investigate The Effects Of Various St||Historical Perspective And Future Projection Of Longwall Min||Analysis Of Longwell Shields And Their Interaction With Surr||In-Situ Performance Analysis Of Immediate Forward Support (I||Australian Longwall Geomechanics - A Recent Study||Strata Support Interaction On A Powered Support Longwall Fac||Geotechnical Constraints On A 6 M Single Pass Longwall||Prediction Of Longwall Support Loading At Southern Colliery,||Pressure Distribution Of 2-Leg Shield Supports||A Simple Finite Element Model For Predicting The Behaviour O||Surface And Borehole Microseismic Monitoring Of Longwall Fac||Rigid Or Yielding Roof Bolts: At The Face Or Away From The F||An Assessment Of Rockbolting In Geologically Disturbed Mine||Load Transfer Mechanisms In Reinforcing Tendons||Innovative Rock Reinforcement Hardware||Innovative Ground Support System||A New Rock Bolting Concept For Underground Roadways||Design Considerations For Cable Truss Secondary Supports In||Influence Of Bolts On Discontinuities And Yielding Rock - Co||Monitoring Indices For The Support And Surrounding Strata Sy||Deformation Of Retreat Gatroad In Interpanel-Pillar System||Optimisation Of Reinforcement Design Of Coal Mine Roadways||How To Cope With Cutter Roof Problem||Horizontal Stress Control In Underground Coal Mines||A Study Of Floor Heave In The Mines Of The Southern Coalfiel||Ground Control Hazard Analysis In Multi-Seem Mining||Convergence And Load Measurements In An Underground Mine In||Detailed Underground Measurements Of Roof Deflection And Bed||Subsurface Fracture Development Due To Longwall Mining And I||Characterization Of Overburden Response To Longwall Mining I||Continuous Monitoring Of Mechanised Breaker Line Supports To||Numerical Modelling Of A Monitored Site In An Underground Co||Reformation Of The Hydraulic Stowing Mining Method||A Study On The High-Water Solidifying Materials For Gob-Alon||Geological Sensing - The Key To Increasing Miner Safety||Cemented Backfill In Two Italian Massive Orebodies||A Possible Alternative To Hardwood Chock Pieces||Ground Control Techniques Utilizing Polymer Grid Structures||Application Of DDM To Some Rock Pressure Problems In Japanes||Evaluation Of The Strength Behaviour Of Monolithic Packs||Probabilistic Stability Analysis Of Embankments And Slopes||Application Of Tailing Sand And Water As Backfill Material I||Subsidence Prediction From The Beginning - Collie Coal Basin||Mining Subsidence Of An Urban Area In Ipswich, Queensland||Investigation Of Subsidence Event Over Multiple Seam Mining||Classification Of Mine-Related Subsidence East Of Mississipp||Influence Of The Sloping Of Ground Surfaces On Mine Subsiden||Effects Of Subsidence On Steep Topography And Cliff Lines||The Effectiveness Of Interpanel Pillars In The Control Of Su||Cross Well Acoustic Tomography To Locate Abandoned Undergrou||Three Dimensional Numerical Modelling Of Effects Of Subsiden||A Comprehensive Computer Model For Predicting Dynamic Subsid||Development Of Void Diffusion Models To Predict Subsidence D||Application Of A Simplified Three-Dimensional Roof-Pillar-Fl||A Design Approach For A Swelling Rock In An Underground Mine||Study Of The Impact Of Mining Under Massive Roof At Datong C||Weak Claystone Floors And Their Implications To Pillar Desig||A Method For Determination Of Strength Of Coal Mass||A Study On Application Of Comprehensive Rock Mechanical Prop||The Mechanical Property Of Coal Containing Gas||The Rheological Fracture Properties And Outburst Mechanism O||Investigation And Analyses Of Sudden Outbursts Of Gas During||A Casting Method For Artificial Rock Specimens||Progress In The Knowledge Of Granite Cutting With Diamond Wi||A Simple Method Of Measuring Rock Fracture Toughness Using T||Mine Stability Evaluation From Microseismic Activity||The Response Of Massive Structures Inferred From Tidal Tilt||Optimization Of Bench Blast Design With The Aid Of Computer||The Directional Drill Monitor For Long Hole Gas Drainage In||Effect Of Drilling Fluid Composition On Penetration Rate||Prediction Of Rock Cutting Performance Using Fracture Mechan||Investigation Into Cutting Characteristics Of Indian Coal Se||Prediction Of Shearer Cutting Performance||Sub-Surface Cracks Due To Disc Cutter Spacing For Improved R|