Mining Project: Empirical Guidelines for Longwall Ground Control Design

Research Summary

Nearly half of all underground coal miners work in longwall mines. These miners face hazards from major roof collapses that can block necessary escape routes and ventilation airways, and from injuries from falls of smaller volumes of rock and coal. Longwall mines depend upon a series of entries for safe access to and emergency egress from the face, and to provide critical ventilation of the working area and mined-out panels. These entries may be as great as 15,000 ft long and subjected to severe abutment pressures. A blockage in any of these entries has significant safety implications for the entire mine. Longwall gateroad stability is critical to prevent tailgate collapses which could lead to fatalities and injuries. Proper pillar design and roof support is critical to stable and safe tailgates.

This project's overall goal was to update the database of case histories upon which the Analysis of Longwall Pillar Stability (ALPS) software bases its recommended stability factors and re-evaluate variables impacting successful pillar design to reflect modern mining scenarios.  The project aimed to  make an important contribution to the PART (Program Assessment Rating Tool) goals of reducing injuries from ground failures by 25% over 5 years, and reducing both fatalities and injuries from ground failures by 50% in 8 years. The project directly addressed Strategic Goal #6 of the Mining Program Strategic Goals for Intramural Research: Eliminate ground failure fatalities and injuries in the mining industry.

Longwall gateroad stability is critical to prevent tailgate collapses which could lead to fatalities and injuries. Proper pillar design and roof support is critical to stable and safe tailgates. The updated ALPS database will ensure the continued value of the ALPS design software, thus maintaining an important design tool for the mining industry.

At the completion of this project, researchers were unable to update the ALPS database with enough cases to warrant revision to the design software, primarily due to limited industry collaboration.  There were too many mines that would not allow NIOSH researchers to either visit the sites, provide the supporting information, or publish their information.  NIOSH was able to present at least one case history that supported the need to refine ALPS for specific conditions experienced in certain locations around the country.