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Peabetq <br />To: Pat Sollars <br />FROM: Anil K. Ray, Ph.D. <br />Murali M. Gadde, Ph.D., P.E. <br />Memorandum <br />DATE: 10/02/2014 <br />Stability of the Gateroad System in the Wolf Creek Seam Under <br />the Wadge Seam Water Pool <br />At the Foidel Creek Mine, the Wolf Creek seam below the old workings of the Wadge <br />seam is proposed to be mined by longwall mining system. The proposed sequence of longwall <br />panels in the Wolf Creek seam are shown in Figure 1. During gateroad devleopment of panel 1, <br />part of the gateroad (shown by ellipse in Figure 1) will be under a water body accumulated in <br />the Wadge seam gob. The question was raised about the potential for this accumulated water to <br />flow into the Wolf Creek seam workings during gateroad development. This report investigates <br />the validity of such a conern by studying the stability of interbuden between the Wolf Creek <br />seam gateroads and the Wadge seam water body using numerical modeling as well as some <br />empirical guidelines. <br />Numerical Modeling <br />To study the stability of interburden and the gateroad system underlying the water body, <br />numerical modeling was carried out with a finite difference software program (FLAC31)). <br />Around the zone of concern (ellipse in Figure 1), the overburden depth of the Wolf Creek seam <br />is around 1750 ft and the interburden thickness is 130ft to 135ft from the overlying Wadge <br />seam. The mining height has been assumed as 8ft and the two rider seams are located at 6ft and <br />17ft respectively above the Wolf Creek seam (Figures 2 and 3). The panel 1 gateroad (tailgate of <br />panel 1) consists of two equal size pillars of 136ft wide (center -to -center) and 200ft long <br />(center -to -center) as shown in figure 4. The entries and crooscuts are 20ft wide. <br />The model geometry used for modeling is shown in Figure 2. The model consists of the <br />floor below the Wolf Creek seam (100ft), the Wolf Creek seam (8ft) and the complete 132 ft <br />interbuden between the Wadge and Wolf Creek seams. One hundred thirty two feet above the <br />Wolf Creek seam lies the water body and Wadge seam gob. The Wolf Creek seam gateroads are <br />located below the center of the gob of the Wadge seam panels. At this location, the gob of old <br />Page #I <br />