If you have access to OneMine as part of a member benefit, log in through your member association website for a seamless user experience.
|Fully-grouted roof bolts comprise more than 80% of the primary roof supports used in U.S. coal mines. However, nearly 1,500 MSHA reportable, non-injury roof falls occur each year, and most of these are attributable to failure of the roof bolt system. Anchorage failure is one failure mechanism for fully-grouted bolts. As roof deformation works its way upward, the bolts can become heavily loaded near their upper ends, If the applied load exceeds the anchorage, the bolts will simply pull out. Research dating back 30 yrs indicates that this type of anchorage failure is most likely when the roof rock is weak, just where roof support is most critical. In soft shale or coal roof, the small amount of data available in the literature indicates that 20-30 in of resin anchorage may be required to achieve the full capacity of the bolt. In other words, the "full resistance zone" of a 60 in bolt may actually be just 30-40 in. Despite its potential importance, there is no widely accepted anchorage test for fully grouted bolts. Standard pull tests have sometimes been employed, but they provide no information on the anchorage near the top of the bolt. An alternative, first described more than 25 yrs ago in the U.S., is the short-encapsulation pull test (SEPT). With this test, the bolt is installed with only a short (1 ft or less) tube of resin. In recent years variations of this test have become international standards. This paper describes recent studies using short encapsulation pull tests in the U.S. Tests were conducted in the National Institute for Occupational Safety and Health (NIOSH) Safety Research Coal Mine at Bruceton and at underground mines in Pennsylvania and West Virginia. The study found that the SEPT can be used to make a simple evaluation of resin bolt anchorage. Suggested procedures for conducting SEPT are included. The study also confirmed that poor anchorage can be an issue, particularly where the roof rock is very weak. Some simple techniques for improving anchorage, and thereby the effectiveness of fully grouted bolts, are discussed.|
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|