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|Overcore measurements at the North Fork Valley (NFV) coal mines in western Colorado have shown that horizontal stresses are highly anisotropic. Measurements have been made in four mines at various depths. In many measurements, the maximum horizontal stress is three to four times higher than the minor horizontal stress. At the West Elk Mine, maximum and minimum horizontal stresses of 24 MPa and 6 MPa, respectively, have been measured at depths of 640 meters (m). Under highly anisotropic stress conditions, ground control problems associated with both high and low horizontal stresses can develop. While high horizontal stresses can produce cutter failures and floor heave, low horizontal stresses can allow block fallouts. This paper summarizes the horizontal stress measurements in NFV mines and, in particular, in the West Elk Mine where their role in roof fall and floor heave failures is discussed. This experience has led to an improved use of ground support and safer mining operations at depths of 640 to 700 m.|
Additional chapters/articles from the SME-ICGCM book 24th International Conference on Ground Control in Mining (ICGCM) 24th
|Keynote Address at the 23rd International Conference on Grou||Analysis and Design of Rib Support (ADRS) a Rib Support Desi||Evaluation of the Impact of Standing Support on Ground Behav||Half a Career Trying to Understand Why the Roof Along the Lo||Forecasting Roof Falls with Monitoring Technologies - A Look||Analysis of Seismic Source Parameters of Roof Falls in Time||A System to Provide Early Warning on Impending Goaf||Outcomes of the Landmark Longwall Automation Project with Re||Application of Phenolic Foam in Longwall Mining||Multiple Seam Mining Interactions: Case Histories from the H||Analysis of Entry Stability Associated with Multi-seam Minin||Failure Mechanics of Multiple Seam Mining Interactions||Engineering Classification of Ultra-close Multiple Seam Roof||Definition of Ultra-close Multiple-seams and its Ground Pres||Depillaring and Roof Bolting Practices at Quinsam Coal Mine||Seam Structure - An Important Criterion for Coal Pillar Desi||Mitigating Longwall Subsidence Effects on a Large Industrial||Impacts of Longwall Mining on Hydrology, Soil Moisture, and||Basics on the Dimensioning and the Extraction of Shaft Safet||Modeling the Arc-effect of a Coal Mine Roof||Recent Advances in Numerical Simulation of Cutter Roof Failu||Test Method for Assessing Water Degradation Potential of Coa||Geotechnical Strata Characterisation Using Geophysical Boreh||A Method for Quantitative Void/Fracture Detection and Estima||Implication of Highly Anisotropic Horizontal Stresses on Ent||Ground Control of a Mine Stope in Weak Rocks Subjected to Hi||Analysis of Highwall Mining Stability - The Effect of Multip||Highwall Mining in a Multiple-seam, Western United States Se||The Slope Stability Assessment in the Wall Overlooking the S||Numerical Modeling as a Tool to Predict Pillar Condition and||Development and Testing of a New Roof Prop||Stability Mapping System||Using Foaming Grout to Stabilize a Ventilation Raise in Very||Roof Control and Roadway Support Design in the #9 Coal Seam,||Non-confirmation Mathematics for Wall Rock Classification fo||The Influence of the First Layer Thickness of Immediate Roof||Studies on Distribution Pattern of and Methane Migration Mec||Development of a New Roof Bolt Technology to Improve Gate- R||Improved Pull out Strength of Fully Grouted Roof Bolts throu||Experimental and Numerical Methodology Assessment of Load Tr||An Investigation into the Support Systems in South African C||Investigation of Fully Grouted Roof Bolts Installed Under In||Development of the Laboratory Short Encapsulation Pull Test||A Resin Quality Testing Procedure for Collieries||Determination of Load Transfer Characteristics of Gloved Res||Fully Grouted Torque Tension Bolts Successfully Support Pitt||Shear Bond Characteristics in Grouted Cable Bolts||Overcoring Techniques to Assess in Situ Corrosion of Galvani||Development of a Laboratory Facility for Testing Shear Perfo||Mechanical Response of Split-Set Rock Bolts in Squeezing Gro||Mechanisms of Rib Sloughing and Methods of Controlling Thick||Supporting Method of the Bolted Strata in Large Deformation||Assessment of Ground Conditions Near a Mine Portal Using Gro||Detection of Abandoned Mines and Air Passages/Burning Center||Detecting Abandoned Coal Mine Entries by High Resolution Ear|