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DEFINITION OF SYMBOLS <br />Symbol Definition Dimensions <br />S Vertical Displacement (Subsidence) L <br />Sm Maximum Vertical Displacement (Sm=a•t) L <br />S/Sm Ratio of Vertical Displacement to L/L <br /> Maximum Vertical Displacement <br />S6 Horizontal Displacement L <br />t Coal Extraction Thickness L <br />a = (Sm/t) Subsidence Factor L2 <br />a~ Subsidence Factor Above Chain Pillars L2 <br />S~ aWt Maximum Subsidence Above Chain Pillars L <br />d Overburden Depth L <br />Sm/d Ratio of maximum vertical displacement <br /> W overburden depth L2 <br />. WQ Critical Extraction Width L/L <br />W/d Mining Width to Overburden Depth Ratio L/L <br />M Tilt (Slope) L2 <br />Mm Maximum Tilt L/L <br />C Curvature, the reciprocal of <br /> Radius of Curvature rad/L (12) <br />Cm Maximum Curvature rad/L (12) <br />E Horizontal Strain <br /> (+) is Positive, (-) is Alegative L2 <br />Em Maximum Horizontal Strain I./I. <br />~ Angle of Draw Degrees <br />B Break Angle Degrees <br />(3 Angle of Major Influence Degrees <br />r Radius of Major Influence L <br />~.~J <br />iv <br />