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• -29- <br />~. <br />,. • APPENDIX C <br />COi7FIIiED CORE PILLAR LOADING ANALYSIS <br />Adapted from: A.H. t7ilson, Research into the deteraination <br />- of pi11az size, Part I, An hypothesis concerning pillar <br />'~ stability, The Mining Engineer, v. 231, n. 141, pp. 409-4I7, <br />June 1972. <br />Terminology Employed <br />p = Pi11az width (ft) ,(= Pillar length (ft) <br />a = Pillar height (ft) 8 = Depth (ft) <br />3 <br />_ r = Density (Ib/ft <br />) ¢ = Angle of internal friction <br />Tan ~ = 1 + Sin, /1-Sin ~ (Passive pressure coefficient) <br />Q--o = Compression strength (psi) at pillar ribside. <br /> (Rock substance cohesion is a conservative estivate.) <br />'- ~V = Vertical stress at seam level (psi) <br />~ <br />_ Maximum stable vertical pillar stress (psi). <br />~ <br />Y = Distance into pillar (ft) <br />Y Distance into pillar at location of maxinum stable <br /> pillar stress (ft), or to edge of confined core.. <br />L Load carrying capacity of pillaz (Tons). <br /> = Average bolting stress applied to pillar edge (psi). <br />t ~ Fill stress applied horizontally at aidheight of <br />`-• pillar (psi) . <br />~ <br />,.. p Angle of repose (surface friction) of fill (o) <br />(_ a'F = Density of fill (lb/£t3) <br />6-F x m tYF r 1- Sin ~F 1 psi <br />~ <br />~ ~ <br />l + Sin F l <br />~~ ^ <br />'•- ~ <br />_ <br />(6.944 x 10-3 ~H +0 F) 7 an ~ + ~ • 2si <br /> <br /> <br />~. n <br />~. <br />Y _ m <br />Tt <br />~ <br /> an ~ ( T an 9 - ! ' <br />^ a a +(~ + ~~ y~ p, <br />Y <br /> <br />(o) <br />