Modern shield technology: better than ever but still not perfect.
Proceedings of the 18th International Conference on Ground Control in Mining, August 2-5, 1999, Morgantown, West Virginia. Peng SS, Mark C, eds., Morgantown, WV: West Virginia University, 1999 Aug; :149-163
A survey of the longwall industry was conducted to examine the performance of modern shield technology. The results of this survey indicate that state-of-the-art shields perform better and last longer than ever before, but premature failures do still occur. In addition, longwall operators are now using shields longer than ever before and a greater number of fatigue related failures on aging shields are now occurring. A generic assessment of these field failures is provided, describing the nature of the failures d how widespread they are throughout the industry. An engineering assessment of shield design and factors that cause field failures is made using both strength of materials and fracture mechanics principles. From this analysis, design practices to improve structural margins of safety and extend the life of the shield are proposed. The existence of unexpected field failures indicate that current shield performance testing is at times inadequate. Recommendations are made relative to improved shield performance testing protocols including the benefits of testing in an active load frame such as the National Institute for Occupational Safety and Health's (NIOSH) Mine Roof Simulator. Even the most rigorous shield testing procedures, which strive to simulate in-service loading conditions, fail to consider key environmental issues, such as corrosion which is often the cause of structural fatigue failures in modern shields. The survey also indicated that hydraulic failures occur much sooner in the life cycle of a shield than structural failures, and although they can significantly degrade support capability, often go undetected for long periods of time. Methods to detect the hydraulic failures are also provided. The paper concludes with key points to maximizing shield design and life expectancy and ideas for future generation shield designs.
Mining-industry; Mine-workers; Miners; Accident-analysis; Accident-prevention; Control-technology; Safety-practices; Safety-research; Longwall-mining; Ground-control; Ground-stability; Statistical-analysis; Mining-equipment; Mining-industry; Underground-miners; Underground-mining
Proceedings of the 18th International Conference on Ground Control in Mining, August 2-5, 1999, Morgantown, West Virginia