ICGCM Papers:
Operator Case Histories
 
 
Effects of Draw Slate Thickness on Longwall Mining
32nd International Conference on Ground Control in Mining
Effects of Draw Slate Thickness on Longwall Mining
by
Jun LuDaniel W SuGregory J HasenfusMark VAn DykeStephen Morgan, Consol Energy Inc., Canonsburg, United States
Download PDF Add to My Library
[Conference] 32nd International Conference on Ground Control in Mining
[Price] Free  [Comments] 0
[Topical Area] Operator Case Histories
[Author] Jun LuDaniel W SuGregory J HasenfusMark VAn DykeStephen Morgan, Consol Energy Inc., Canonsburg, United States
[Abstract] 
Key Conclusions:
fiogf49gjkf0d
In the Pittsburgh coal seam, the drawslate is generally inconsistent and very weak. When the drawslate is very thick, it will adversely affect the safety and productivity at the longwall face. From Consol Energy’s longwall mining experience, the critical thickness of the drawslate which may affect longwall mining is about 2.5ft. When the drawslate thickness is more than 2.5ft, longwall productivity will be adversely affected; the thicker the drawslate, the slower the face advance rate. Double-pull the shield behind the drum will reduce the tip-to-face distance and roof exposure, resulting in better roof stability at the longwall face. In order to mitigate the effect of the thick drawslate, it’s important for mine management to maintain a steady advance rate, and reduce the face down time (like bunker down, belt down, weekend, and power move, etc.) as much as possible.
Key Findings:
fiogf49gjkf0d
From the on-site geological mapping, it’s possible to predict the drawslate thickness in the future longwall panel, which will help mine management to take proactive actions when mining through those areas. On-site geological mapping also shows that when the drawslate thickness is more than 2.5ft, productivity at the longwall will be affected. As the drawslate thickness increases, the effect will be more severe. Results from the numerical models show that as the drawslate thickness increases, more drawslate will fall at the face. Double-pull the shields behind the drum will reduce the tip-to-face distance and roof exposure, resulting in better roof stability at the longwall face.
Objective of the Paper:
fiogf49gjkf0d
In order to predict the trend of the thick drawslate and mitigate the effect of the thick drawslate, geological mapping was conducted in the development sections and the longwall face. Based on the geological mapping, the thick drawslate areas were recorded, and the collected information was used to predict the drawslate thickness in the future panels. The thick drawslate map will be useful for guiding mine management and the longwall crew when mining through those areas. On the other hand, numerical models have been conducted to analyze the effect of the thick drawslate and shield double-pull on the face conditions. Different drawslate thicknesses of 1ft, 2ft, 3ft, 4ft, and 5ft and tip-to-face distances of 12 and 28 inches were modeled using the Rocscience FE software to analyze the stress distributions and yield conditions at the longwall face.
Problem Statement:
fiogf49gjkf0d
The Pittsburgh Coal Seam is the thickest and most extensive coal bed in the Appalachian Basin; hence, it is the most important coal bed in the eastern United States. The coal bed typically insists of a roof coal, a drawslate of variable thickness and the main bench. In southwestern Pennsylvania, the roof coal is about 2ft thick, and the main bench is about 5ft thick. The drawslate, on the other hand, is quite variable. In some locations, the roof coal may totally disappear and the drawslate may become very thick, sometimes up to 4 or 5 ft. Since the drawslate is very weak and tends to fall away from the face, presence of thick drawslate may severely affect the longwall productivity and safety.