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|The data base of failed pillar cases as used by Salamon and Munro (1967) in their original analysis to determine the strength of coal pillars empirically, has been updated for this study. It is shown that the Vaal Basin and Klip River coal fields exhibit similar behaviour, i.e. failure at high safety factors within a short period of time after their creation. Those collapse cases have been omitted from the new data base. New failures that occurred after 1967 have been added, except for those that occurred in the Vaal Basin and Klip River coal fields. (1967) a technique to minimise the area of overlap between the populations of failed and intact pillar cases, the new data base was re-analysed in conjunction with the original Salamon and Munro (1967) data base of intact pillar cases. It was found that a linear formula reduced the overlap area by 22%. The new formula predicts higher strength for pillars with a width-to-height ratio greater than approximately 2S and a lower strength for smaller pillars. For most current South African coal mining conditions, using the new formula for pillar strength will result in leaving smaller pillars without sacrificing stability. The reason for this is that the Salamon and Munro (1967) formula underestimated the strength of larger pillars and overestimated the strength of smaller pillars. The potential benefit for the South African coal mining industry amounts to saving reserves equal to the total production of two large mines per year.|
Additional chapters/articles from the SME-ICGCM book Proceedings 21st International Conference on Ground Control in Mining
|Pre-Driven Experimental Longwall Recovery Room Under Weak Ro||Longwall Mining-Induced Abutment Loads and Their Impacts on||Influence of Structural Stress Concentration and Structural||The NIOSH Shield Hydraulics Inspection and Evaluation of Leg||Study on Top-Coal Loss and the Optimum Drawing Interval of L||Stress Measurements for Safety Decisions in Longwall Coal||Re-Use of Rectangular Bolted Roadways in a Cover Depth > 100||Numerical Modeling of the Gob Loading Mechanism in Longwall||Deep Cover Pillar Extraction in the U.S. Coalfields||Evaluation of Pillar Recovery in Southern West Virginia||A Case History Investigation of Two Coal Bumps in the Southe||A Linear Coal Pillar Strength Formula for South African Coal||Anchorage Pull Testing for Fully Grouted Roof Bolts||Comparison of Some Aspects of Bolting Mechanisms Between Ful||Eclipse System Improves Resin Anchored Rebar Bolting||Design Considerations for Tensioned Bolts||Field Testing of the Fully Grouted Thrust Tensioned Bolts||Improvement in Pre-Tensioning of Strand Bolts in Australian||The Introduction of Roof Bolting to U.S. Underground Coal Mi||Support of Coal Mines in the United Kingdom||The Use of NDT Methods to Determine the Condition of Rockbol||Rockbolted Support of Retreat Longwall Gateroads at 1000m De||Roof Screening: Best Practices and Roof Bolting Machines||Numerical and Physical Modeling as Planning Tools for Rockbo||Stone Mine Design in Highly Fractured Rock||The Importance of Underground Stone Mine Roof Geology||Utilization of Ground-Penetrating Radar to Determine Roof Co||An Examination of the Loyalhanna Limestone's Structural||Highwall Stability in an Open Pit Stone Operation||Overview of Safety Considerations with Highwall Mining Opera||Highwall Monitoring to Combat Rockfall Accidents at Opencast||Seepage and Reinforcement Behavior of Grouting Into Slaking-||Floor Heave in Shallow Room-and-Pillar Mining||Analysis of a Stability Problem in an Underground Coal Mine||Comparison of Acoustic Emission and Stress Measurement Resul||Acoustic Scanner Analysis of Borehole Breakout to Define the||Estimating Rock Strengths Using Drilling Parameters During R||New developments with the coal mine roof rating||Application of geotechnical and geophysical parameters to im||Development of a Risk Rating System for Use in Underground C||Empirical and analytical design of large openings at a propo||Shear Mechanism for Mining-Induced Fractures Applied to Rock||Evaluating Techniques for Monitoring Rock Falls and Slope St||Developments in Sealant Support Systems for Ground Control||Stability Control of Clusters of Deep Openings Around Shaft||The Use of Pneumatic Stowing in Germany Considering Subsiden||A 3-D Semi-Analytical Method for Subsidence Prediction and S||Theory and Technology of Mining Subsidence Control by Grouti||Surface Subsidence Due to the Combined Effects of Undergroun|