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|In the 1990s the German mining industry introduced a new generation of shield supports. The new design of support has a maximum load capacity of 10,000 kN, making these units as strong as the shields used in Australia and in the USA. DMT took more than 3,100 underground observations in order to verify the roof fall frequency by statistical analysis. The results of this work have led to practical recommendations for roof control and the required shield support system on longwall faces. The underground observations have been correlated to Rock Mass Classification, to stress calculations and to the angle between the direction of the fissures and the direction of longwall mining_ The analysis work yielded the following two sets of results: 1. There is a critical distance between the canopy tip and the coal face (Tip to Face TF,n,). The TF,n, is predictable and relates to: the thickness of the first roof layer and its uniaxial compressive strength. The face support should have a TF that is less than the TFcrtt in every underground longwall situation. Exceeding the TF crit call immediately result in a roof fall. 2. Using the obtained regression equation DMT is able to calculate the probability of the roof fall frequency (FF), which describes the roof fall sensitivity. When TFcr;, is exceeded the predicted roof fall FF relates to: the measured support resistance (MSR) of the shield support the calculated vertical stress (p?) the fissure-direction index (DI = angle between main fissure direction and direction of mining) and the distance by which TFcrit is exceeded (ATF). Armed with these results DMT is now able to predict the critical distance between the tip of the canopy and the coal face (TFcrit), as well as the roof fall frequency, for all shield designs. By applying the new calculation method it is now possible to compare alternative longwall layouts and different shield support types under pre-set geological conditions. Mining engineers on site are therefore in a position to make the necessary roof control preparations required to run the longwall operation to maximum efficiency. The results provide a useful basis for making practical recommendations and for selecting the most effective design of shield support. The paper uses practical examples to demonstrate the R&D results and present the various methods now available for calculation and prediction in longwall roof control.|
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|