PURPOSE:  To develop engineering guidelines for underground mine ventilation stoppings that will help to ensure the compatibility of these structures with in-service load conditions to prevent premature failures that can lead to disastrous conditions. A secondary objective is to develop light-weight materials into satisfactory construction designs to reduce the potential of material handling injuries.

RESEARCH SUMMARY:  Nearly all commodities of bedded deposit formations mined by underground methods use some form of permanent stoppings to control ventilation. Hundreds of thousands of these critical structures are constructed each year in underground mines. Failure of these structures can lead to disastrous fires and mine explosions. The current focus of this work is to develop engineering design guidelines for stopping construction in underground coal mines. The current Code of Federal Regulations (CFR) protocols do not fully address the in-service load conditions for these ventilation control structures and allow a wide range of stopping designs with varying transverse load capabilities to be installed in any mine environment. This can lead to dangerous conditions where the ventilation control capability can be less than expected and inadequate in certain conditions. New protocols that will provide a parametric study of the variables that impact the loading and stability of these structures need to be developed and discussed with the Mine Safety and Health Administration’s Technical Support. This will lead to more relevant design guidelines for stoppings that will ultimately provide for safer mining conditions by constructing stoppings suitable to control normal ventilation pressures and certain levels of over pressurization when the need arises. The preliminary research efforts have shown that arching is a more valid representation of the loading behavior that occurs in the mine compared to the free-standing analysis currently considered in the CFR. It has been demonstrated that arching can increase the transverse load capacity of stoppings by more than an order of magnitude. A new protocol to evaluate the transverse loading capability of stoppings through biaxial half-wall testing of dry-stacked block stopping constructions in the Mine Roof Simulator load frame has been developed and verified through full-scale testing in both the NIOSH Experimental Coal Mine and Lake Lynn Laboratory. Preliminary design equations have been developed for conventional dry-stacked block stoppings from this work and complete design guidelines prepared at the conclusion of the project.