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A Case Study of Gate Pillar Response to Longwall Mining in Bump- prone Strata.
Longwall USA PP 92-105 :92-105
This U.S. Bureau of Mines paper reports on an investigation of strata movements and coal pillar behavior in two different longwall gateroad designs within a bump-prone mine. The study area is located in the Pocahontas No. 3 Coalbed under approximately 2,000 ft of overburden which includes several massive layers of very competent sandstone. The first gateroad investigated was a yield- abutment-yield design containing two 30-ft-wide yield pillars and an 80-ft-wide abutment pillar. In the past at this mine, the abutment pillars in this gate design have been known to bump under tailgate loading. In an effort to alleviate this bump hazard and to standardize their gateroad design, the mine switched to an alternative yield-abutment-yield configuration consisting of two 20- ft-wide yield pillars and a 120-ft-wide abutment pillar. In the study of these two gateroad designs, eight yield pillars and four abutment pillars were instrumented with a total of 118 hydraulic coal cells, 133 convergence stations, and 8 multiple-point coal extensometers.
Longwall USA, PP. 92-105