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Model results <br />The main objective of the modeling was to study the stability of the interburden rock below the <br />water body. The model was first solved with virgin conditions to establish the in-situ stresses and <br />then again solved after gateroad development. <br />The laboratory determined strength, as shown in Table 1, is scaled down to the rock mass level <br />by using the approach presented by Gadde et.al. [1]. For this case, a strength reduction factor of <br />1/4t' has been used to estimate the rock mass strength. <br />The local safety factors (SF) estimated along sections AA' and BB" are shown in figures 6 and 7. <br />From the modeling results it can be seen that the immediate roof up to a maximum distance of 7 <br />to 8ft have a safety factor less than 1.0 at the intersection (This is without incorporating any <br />primary supports). The zone of SF less than 1.0 is strictly limited to the first rider seam above the <br />Wolf Creek seam. Apart from these zones, the remaining interburden has a safety factor well <br />over 1.0. Further, when the rider seam is not present in the immediate roof, which is the case for <br />a considerable mining area in the Wolf Creek seam, the stability of the immediate roof will <br />increase significantly. <br />In summary, the modeling results show that except for a small region in the immediate roof of <br />the Wolf Creek seam, the rest of the interburden will remain very stable and thus the chances of <br />seeing any massive intersection failures in the Wolf Creek seam development workings are <br />negligible. In the absence of a large roof failure with the ability to create a sink hole, the upper <br />seam water body will pose no safety threat to the Wolf Creek development mining. Therefore, it <br />is concluded that the gateroad development in the Wolf Creek workings underneath the Wadge <br />seam water pool can be done safely. <br />Page 47 <br />