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|A breaker line support (BLS) monitoring system, BLSmon, has been designed and constructed by the CSIRO and installed and commissioned at Laleham No.1 Colliery, Queensland. This system was designed to record hydraulic leg pressure and canopy position measurements and relay these, in real time, to the surface. The system has shown itself to be capable of operating on the BLSs without any adverse affect on production, Analysis of the results of the monitoring exercise has shown that rate of change of leg pressures on the BLSs could be used as an aid in the prediction of adverse mining conditions. Under favourable mining conditions the supports were observed to initially unload from the set pressure, this unloading reduced with time and by the end of a typical lift cycle had either ceased or reversed slightly. This behaviour was considered to be due to one of four possible causes, these being; the compaction of floor debris, and/or compaction of the floor, and/or crushing of the roof and /or support creep. The actual cause can only be determined through detailed monitoring of both roof and support convergence. However observational data would suggest that compaction of debris and softened floor material beneath the supports was the most likely cause. The few positive loading rates recorded under these conditions were of short duration and occurred towards the end of individual lifts. Where mining conditions were unfavourable the negative rates of change of pressure, unloading of the support, were reduced throughout a lift, in both duration and magnitude, when compared with favourable mining conditions. Over the same period the positive rates of change were observed to be greater. The rate of change of loading and convergence can be utilised to identify the onset of instability in the lift area. However, before this facility can be utilised by the mine for the reliable prediction of instability more monitored data and sophisticated processing techniques are required. A mechanism has been postulated for the deformation behaviour of the roof and pillars in a mechanised pillar extraction operation from the continuously monitored data, observational data and results of previous studies. The 7 m wide fenders were observed to yield under abutment stresses before lifting commenced. The stability of these fenders throughout the lifting sequence was considered to be dependant upon the magnitude of their post peak load carrying capability. This is influenced by the post peak stiffness and the extent of roof lowering in the vicinity of the fender. Difficulties with fender extraction occurred where remnant coal left standing in the goaf caused uncaved goat to bridge to the mined fender. Difficulties were also experienced where sub-vertical jointing occurred in the roof of the split reducing it's ability to bridge effectively. Despite the relatively short monitoring period, the potential role and application of continuous monitoring in advancing understanding of the rock mass response to mechanised pillar extraction operations has been demonstrated. This understanding now requires enhancement and shows great potential for aiding the optimisation of mechanised pillar extraction operations.|
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|