Underground stone mines in the United States make use of the room-and-pillar method of mining. A prerequisite for a safe working environment is that the pillars should adequately support the overburden and the pillar ribs and rooms should remain stable during ...

It was found that current mine layouts have been successful in providing support to the overburden, while a small number of isolated pillar failures were observed. The stable pillar layouts and failed pillars were plotted on a chart that demonstrates the relationship ...

Limestone formations in the United States can be subject to relatively high horizontal stresses owing to the existence of tectonic loading of the limestone strata. Underground limestone mines use the room-and-pillar method, in which 12- to 18-m-wide rooms ...

Various surface controls are used in mines to control the roof skin. One control that has proven to be very effective is roof screening. Roof screen effectively controls roof skin and provides a high roof surface coverage. Although many mines are reluctant ...

This paper describes recent studies using short encapsulation pull tests in the U.S. The study found that the SEPT can be used to make a simple evaluation of resin bolt anchorage. Suggested procedures for conducting SEPT are included. The study also confirmed ...

At a mine in central PA, high horizontal stresses have caused long running roof falls resulting in hazardous conditions for the miners and the premature abandonment of panels. Because of these conditions, the mine requested assistance of the National Institute ...

Despite more than half a century of experience with roof bolting, no design method has received wide acceptance. To begin to improve this situation, National Institute for Occupational Safety and Health (NIOSH) conducted a statistical study of roof bolt performance ...

An accurate assessment of the vertical stress on a coal seam at depth is important for mine design. Vertical stress calculation techniques presently available either are not sufficiently accurate or cannot handle complex surface topography. Therefore, the ...