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Figure 24 <br /> Subsidence Calculations, Monitoring Point MC-2 and Longwall 101 <br /> MC-2 is over the tailgate-startline corner of longwall 102 and down- <br /> dip from longwall 101, No. 1 mine. Point subsided significantly be- <br /> tween 1981 and 7/3/84, by which time it was almost stable (longwall <br /> 101 mined mid-late 1978) . Movement resumed with extraction of 102. <br /> Apparent angle of draw was calculated with reference to 101. <br /> Distance from 101 headgate (x) : 132 ft. <br /> Surface elevation MC-2: 11,696 ft. <br /> Coal elevation, 101 headgate: 8,992 ft. <br /> Surface elevation over 101 headgate: 11,640 ft. <br /> Depth to coal (H) : 2,648 ft. <br /> MC-2 x <br /> �y <br /> :Hanco scale <br /> . A <br /> • longwall 101 <br /> longwall 102 OORpac walls A bed <br /> Slope angle (0) : <br /> 0 = tan-1 x <br /> = tan-1 56 <br /> 132 <br /> = 22.99° <br /> Apparent angle of draw to MC-2 (A; subsided) : <br /> 9 = tan-1 x <br /> Hcos29 <br /> = tan-1 132 <br /> 2648cos222.99 <br /> = tan-1 132 <br /> 2648 0.85 <br /> = tan-1(0.06) <br /> = 3.370 <br />