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|Knowledge of the magnitude and direction of the horizontal secondary principal stresses is a critical factor in designing the layout and mining sequence of underground openings. Typically, horizontal stress measurement has been accomplished using overcoring or hydraulic fracturing. Hydraulic fracturing can be accomplished from surface boreholes prior to development, but the technique relies on numerous assumptions regarding the rock mass and the stress field, and interpretation of results is somewhat subjective. Traditional overcoring provides a more precise measurement, but requires underground access. To allow for precise measurement of the horizontal stress field from surface boreholes, the In-situ Stress Tool (1ST) was developed by SIGRA Pty of Brisbane, Australia. Used in conjunction with HQ wireline coring, the 1ST contains a battery-powered data logger that records tool orientation and monitors six diametral deformations as the tool is overcored. The IST has been used successfully for several years in Australia, but has only recently been introduced in the United States This paper discusses how the IST was used to measure the pre¬mining horizontal stresses at a western U.S. coal mine. Seven successful measurements were obtained in two holes at depths ranging from 250 to 800 ft. Results were consistent, showing moderately biaxial stresses greater than those expected from gravity loading, but relatively low compared to rock strength. In addition to describing the overcoring equipment and procedures, various problems encountered during testing and the accuracy of the results will be discussed.|
Additional chapters/articles from the SME-ICGCM book 23rd International Conference on Ground Control in Mining (ICGCM) 23rd
|Geomechanical Criteria of Longwall Face Support Selection at||Rock Fracture, Caving and Interaction of Face Supports Under||Effect of the Approaching Longwall Faces on Barrier and Entr||Computer Simulation of Ground Behaviour and Rock Bolt Intera||lnterpanel Barriers for Deep Western U.S. Longwall Mining||Application of Yieldable and Cuttable Pump Crib in Longwall||Field Testing of a Real Time Roof Mapping Drilling Display S||Problems in "Void" Detection in Coal Mine Water Hazards||Violent Coal Pillar Collapse -A Case Study||Stooping Low Safety Factor Pillars at Goedehoop Colliery - 1||Laboratory Strength Testing of Coal from Selected Illinois S||Downhole Overcoring Stress Measurement at a Western Undergro||Effect of In Situ Stresses on the Stability of Coal Mine Dev||SOMA: A New Method to Calculate the Operative Stress Field:||Numerical Modeling for Increased Understanding of the Behavi||Evaluation of Rockburst Hazard from Core Testing||Investigation of Electromagnetic Emissions in a Deep Undergr||Development and Application of Geotechnical and Rockmechanic||Laboratory Testing of Rib Straps||The New Two-Dimension LaModel Program||Risk Assessment: Multiseam - Single Seam Mining||A Method To Determine Expander Spacing For Steel Pipelines I||A Case Study Of Abandoned Mine Subsidence At Dominion, Nova||Spatial Trends In Rock Strength - Can They Be Determined Fro||Development And Demonstration Of An Alternate Mining Geometr||Evaluation Of Polyurethane Injection For Beltway Roof Stabil||Application Of Ground Penetrating Radar To Evaluate The Exte||A Risk Assessment Tool For Open Cast Mining In South Africa||Analysis Of Practical Ground Control Issues In Highwall Mini||Preventing Falls Of Ground In Coal Mines With Exceptionally||Geo-Mechanical Property And Failures Of Weak Roof Shales In||Eclipse System Bolting In The Illinois Basin||Variation In The Load Transfer Of Fully Encapsulated Rockbol||Bolt Load Changes During Initial Face Advance And Cross-Cut||Coal Mine Primary Support Selection: Tension Versus Non Tens||Improving Stope Support At Modikwa Platinum Mine||3D FEM Simulation For Fully Grouted Bolts||An Investigation Into The Effectiveness Of Support Systems C||Hydraulic Prestressing Units: An Innovation In Roof Support||Improving Roof Truss Performance||Coal Combustion Byproducts-Based Artificial Mine Supports -||The Influence Of Horizontal Stress On Pillar Design And Mine||Investigation Of Pillar-Roof Contact Failure In Northern App||Mapping Hazards With Microseismic Technology To Anticipate R||Practical Detection Of Underground Mine Roof Failure||Heat-Imaging Experimental Study Of Reducing Local Gas Accumu||Microcirculation Theory Analysis Of Spontaneous Combustion O|