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Results 71 - 80 of 128
10/1/2006 - Technology NewsDescribes the Roof Fall Risk Index (RFRI), a method of systematically characterizing the risk of roof falls in underground limestone mines.
Load Capacity and Stiffness Characteristics of Screen Materials Used for Surface Control in Underground Coal MinesNIOSH conducted an evaluation of screen materials commonly used in U.S. coal mines to determine their support characteristics and identify the parameters that could affect their performance with respect to controlling the fall of rock from the roof.
NIOSH conducted wet/dry immersion cycling of clay-rich rocks, which provides an accurate, quick and inexpensive method for estimating the moisture sensitivity of mudrocks. With this information mine operators can begin to anticipate hazardous ground.
The Roof Fall Risk Index helps the underground stone mine operator to assess defects of the mine strata and rate the relative roof fall risk these defects pose. This paper shows how the defect information is collected and methods to analyze the data.
3/27/2006 - Conference papersA methodology to assess the risk for a roof fall is proposed in a preliminary fashion based on engineering judgment acquired from extensive underground stone mine experience and examination of related literature.
Results show that the remnant upper seam structure's size can influence multiple seam interaction. Specifically, smaller critically loaded upper seam pillars appear more likely to cause lower seam ground control problems than wider pillars.
Monitoring technology and techniques can provide a means to warn of hazardous roof fall conditions. Measuring roof deflection is the most common method of detecting roof instabilities.
The objective of this work was to determine if GPR could be used to help assess the mine roof conditions near the No. 4 Portal area of the NIOSH Lake Lynn Experimental Mine (LLEM).
6/1/2005 - Conference papersThis study used microseismic emissions to help identify three local rock failure processes. It was also shown that analysis of microseismic emissions can aid in assessing the degree of instability associated with these local rock failure processes.
This 7-minute video with instructional material shows how well roof screen keeps loose rock from falling in difficult roof conditions.