Development and Application of Impact–Resistant Lagging for Steel Sets Installed at Underground Roof Fall Areas

摘要

Underground mines often experience roof falls in entries,crosscuts, and intersections of active mining sections, maintravel ways, and belt entries. Roof fall heights greater than 20 ft(6 m) make re-bolting of the newly exposed roof dangerous andimpractical. To protect mine personnel, belts, moving vehicles,and other facilities, mine operators typically install steel structuressuch as square or arch sets in the roof fall areas. Wood laggingis usually installed between the steel-sets to enclose the area andprotect the entry from recurring falls. Usually the void space abovethe steel-sets and laggings is backfilled. However, backfillinghigh roof fall voids is costly, which causes some operators toleave the voids open. In this case, durability of wood over timeand the capability of the steel-set and wood lagging to resistfalling rocks are unknown. During the last few years, KeystoneMining Services, LLC (Jennmar Corporation affiliate engineeringcompany) designed, tested, and developed an impact-resistantlagging system to protect steel-sets1. Various steel-sets protectedwith the impact-resistant lagging were approved by MSHA andinstalled in different underground roof fall rehabilitation projects.This paper presents (1) design, development, and laboratory testingof the patent-pending impact-resistant lagging panel, (2) steel-setdesign methodology according to the American Institute of SteelConstruction (AISC) national standard, and (3) impact-resistantsteel-set design method based on Law of Conservation of Energy.Two underground cases are reviewed to demonstrate the successfulapplication of the impact-resistant lagging system.