2010-04-16_PERMIT FILE - C1996083

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• The existing orientation of the mains is also favorable with respect to major joints and cleats (approximately N70° E). At 30° deviation from the cleats, the potential for joint - induced roof and rib instabilities are reduced. 4.2 Pillar Stability Pillars stability was evaluated using an estimate of pillar strength and stress. Pillar strength was estimated using a method developed by NIOSH (Mark and Chase 1997). Pillar stress was calculated using a numerical model. The modeling resulted in vertical stress distributions on the Upper B seam, including variations in topography, and mining geometry. Pillar factor of safety was calculated during the development work beneath the stream valley by dividing pillar strength to stress. The pseudo- three - dimensional boundary- element code MULSIMTI was used for calculating stress distributions over the area of interest. This proprietary program incorporates elastic, strain - softening material and is suitable for multiple -seam excavations in dipping seams and variable topographies ( Maleki 2002). Model input is shown in table 5 for this elastic analysis. Figure 1 presents the planned mining geometries and the location of detailed models. Mining geometry includes a set of mains being driven under the drainage. The total modeled area is three times larger than shown in figure 1. Modeling results are presented as vertical stress and factor of safety levels (figures 15 and 16). In figure 15, square elements are 6- by 6- by 9 -ft coal elements, the color of which depends on the stresses acting on them. Figure 16 presents the factor of safety for each element while individual pillar dimensions and mining height are considered (9 -ft). Pillar strength is calculated using Mark - Bieniaswki formula (Mark and Chase 1997), which depends on pillar dimensions and the excavation height. • Maleki Technologies, Inc. Page 28