PURPOSE:  Minimize hazards associated with water/slurry impoundments in an underground coal mine by developing a set of guidelines that discuss physical, geological, structural, and safety issues for consideration when designing a safe and efficient bulkhead system.

RESEARCH SUMMARY:  While much progress has been made in preventing disasters in mines, inundations still occur and have the real potential of producing multiple fatalities. Many mining operations rely on bulkheads or ventilation seals to provide a barrier between impounded water and active mine works. Since 1995, there have been over 100 inundation accidents reported by MSHA where mining has cut into underground bodies of water. These inundations serve to illustrate the potential risk to miners while working near such large impoundments.

NIOSH personnel met with personnel at (4) Mine Safety and Health Administration (MSHA) District Offices, the West Virginia Office of Miners’ Health Safety and Training, and Pennsylvania’s Department of Environmental Protection to document locations of bulkhead installations. While in the field, researchers toured mining operations in WV, MD, KY, and AL to gain first hand knowledge of operational issues related to bulkheads. Deep mine inspectors, permit reviewers, mining engineers, design engineers, and bulkhead construction firms were also contacted to better understand the permitting process. To date, in-depth reviews of 28 permit applications have been completed. The data from permit reviews along information gathered during site visits has been entered into a comprehensive Bulkhead Installation data base containing information on existing bulkhead designs and performance case histories. The data base is helping researchers identify trends in design, intended purpose, pressure rating, emergency relief options, and emergency response plans. Full scale hydrostatic testing of mine ventilation seals that can be exposed to hydraulic pressures was conducted at the Lake Lynn Laboratory to provide data on leakage rates and failure mechanisms. Uniaxial compressive testing was performed on core samples taken from the test ventilation seal. The field information and full scale testing data will be culminated into a comprehensive design manual that considers the strength of the bulkhead structures and addresses the parameters that affect the system design such as overburden depth, barrier pillar strength, proximity to adjacent mine works and surface impoundments, method of reducing water elevation, evacuation routes, and emergency planning.

The expected outcomes are: (1) better evaluation measures for bulkhead designs; (2) improved designs that interface with mine strata to better protect miners from a massive in-rush of water or mine waste; (3) identify key factors that have resulted in successful bulkhead designs and rock interfaces over the last 15 years.