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Height of chimney (z) =4 <br />(k - 1) (d2) <br />where: <br />h <br />k <br />w <br />= <br />= <br />= <br />mining height (m) <br />Bulking Factor <br />roadway width(m) <br />=Angle of Repose of the caved rock <br />Pillar Pillar <br />Pillar Pillar <br />Pillar Pillar <br />h <br />t <br />d <br />d W d = (W x 1.414) <br />W <br />d <br />d = (W x 1.414) <br />Surface Section View <br />Plan View (Intersection)Plan View (Entry) <br />Chimney <br />Chimney <br />[2(w)(h 2) cot Ø + h(w 2)] <br />Chimney <br />5174 Highway 133Somerset, CO 81434Operated by Mountain Coal Company, L.L.C.A subsidiary of Arch Resources, Inc. <br />feet <br />0 NTS <br />BYDATE <br />BY <br />GBG <br />REVISED <br />DATE <br />12/7/20 <br />DRAWN <br />SCALE FILE NO. <br />Path: W:\MCC-ENGINEERING\ENG(E)\UNDERGROUND(U)\ROOF <br />SUPPORT(RS)\ROOFSUPPORT(600) <br />20EURS600.DWG <br />Figure 1 <br />Mechanism of Chimney <br />Development above an <br />Intersection and Roadway in a <br />Development Mining Section <br />(Whitaker and Reddish, 1989) <br />WEST ELK