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|Pumpable roof supports provide an alternative longwall tailgate roof support and have grown in usage during the past few years. Heintzmann Corporation has been installing pumpable roof supports at the RAG Resources Emerald Mine in western PA since 1998, where they have provided effective roof control in their longwall tailgates. Despite the success of these supports in this application, questions remain regarding critical design issues for optimizing the use of this support technology. The support loading profile is characterized by a high initial stiffness with peak loading occurring at less than one inch of convergence, followed by significant load shedding with a post failure capacity comparable to that of wood cribbing. Therefore, the key to optimizing the support utilization is to provide sufficient load density to prevent convergence from occurring beyond the peak loading capacity. This requires an understanding of how the supports interact with the ground conditions, hence measurement of the ground reaction curve. In order to obtain this information, pumpable roof supports were instrumented to measure support loading. Roof deformation and roof-to-floor convergence measurements in the vicinity of the instrumented supports were also made. The experimental parameters for the installation were the support spacing and water¬to-solids ratio of the grout, which controls the grout strength and ultimately the maximum capacity of the support. The study clearly shows that at this mine a 24-inch diameter support is fully capable of providing adequate ground control under depths of cover of 750 ft as only 50 pct of the available support capacity was utilized outby the longwall face. It was also shown that the 2.00 to 1 water¬solids ratio, despite providing a slightly softer support response, is sufficient for maintaining the same degree of roof control provided by the traditional 1.75 to 1 grout mix. The 10-ft spacing of the supports did not cause any ground control problems outby the face. However, inby the face the performance of the support is degraded once the peak capacity of the supports is exceeded. It appears that the large load shedding behavior, which is characteristic of this support following peak loading, allows the immediate roof to separate. When this happens, the support is unable to regain control of the roof in time to prevent failure of the immediate roof beam.|
Additional chapters/articles from the SME-ICGCM book 22nd International Conference on Ground Control in Mining (ICGCM) 22nd
|Pillar Design and Roof Support for Controlling Longwall Head||Stress Analysis and Support Design for Longwall Mine-Through||The Utilisation of Numerical Modelling to Predict Water and||Longwall Roof Fall Prediction and Shield Support Recommendat||Comparison Of Multiple And Single Entry Roadways For Highly||Numerical Modeling Of Longwalls In Deep Coal Mines||The Characteristics Of Mining-Induced Fractures In Overlying||Design And Experience Of Total Extraction Room And Pillar Op||Using Site Case Histories Of Multiple Seam Coal Mining To Ad||Mining Method For Extracting An Eight Metre Coal Horizon Con||Stooping Low Safety Factor Pillars At Goedehoop Colliery||Modelling Of Pillar Stability In Room And Pillar Mines||Pillar Optimization For Initial Design And Retreat Recovery||Application Of RMT's Remote Reading Telltale System To||Rock Mechanics Study Of Lateral Destressing For The Advance-||New Tools For Roof Support Evaluation And Design||Considerations For Using Roof Monitors In Underground Limest||Mine Roof Geology Information System (MRGIS)||Imaging Ahead Of Mining With Radio Imaging Method (RIM-IV) I||Geophysics For The Detection Of Abandoned Mine Workings||Investigation Of Seam Thickness And Seam Splitting Within A||Determination Of Rock Strength Properties Using Geophysical||RQD from the Barrel to the Box: Weatherability May be a Bett||A probabilistic approach to ground support design in undergr||The Requirements of a Database to Store Geotechnical Data to||Variation of Horizontal Stresses and Strains in Mines in Bed||Geotechnical Planning Basis for the Optimization of Workings||Tensile roof failure arising from horizontal compressive str||Study of load transfer capacity of bolts using short encapsu||Intersection Stability and Tensioned Bolting||Premature Rock Bolt Failure Through Stress Corrosion Crackin||Short-encapsulation Pull Tests for Roof Bolt Evaluation at a||Field Test with Strain-gauged Friction Bolts at the Gold Hun||Directional Rock Bolt Pullout Tests as Index Tests for Estim||Eclipse Bolting System||The Application of Pre-tensioned Grouted Tendons at Harworth||Investigation into the Extent and Mechanisms of Gloving and||Developments in Improving the Standard of Installation and B||Development of Geotechnical Procedures for the Analysis of M||Recent Developments in the Use of Seismic Tomography in Long||Pumpable Roof Supports: Developing Design Criteria by Measur||Design Considerations of the Secondary Roof Support for Long||The Effect of Standing Support Stiffness on Primary and Seco||Numerical Modeling of the U1A Complex at the Nevada Test Sit||Rock Mechanics and the Analysis of Underground Mine Stabilit||A Study of Potential Fault Reactivation and Water Intrusion||The Elimination of Rock-fall Fatalities in Ontario Hardrock||Root Causes of Groundfall Related Incidents in U.S. Mining I||Analysis on the Dynamics of Mining Subsidence in Range of a||Mitigating Subsidence Influences on Residential Structures C||Influences of Longwall Subsidence on a Guyed Steel Tower - A||Surface Movement of Super-wide Longwall Panels Using Top-coa||New Approach to Evaluate the Stability of Yield Pillars||Experimental Study of Acoustic Emission Characteristics for|