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concentric rings arotu-d the point with the outer radius of the circle being a <br /> function of the angle of draw and the overburden thickness. The subsidence is <br /> obtained frwn summation of the portions of each zone or ring extracted multiplied <br /> by its particular zone or subsidence factor. This particular method utilizes <br /> seven zones of influence for extracted areas. The effects of coal pillars are <br /> determined by the use of a compensating influence function based on a circle <br /> divided into five concentric zones. The technique is readily cauterized and <br /> requires the following minimum information: <br /> 1. A defined area in which values for subsidence are required. <br /> 2. A description by rectangular coordinates of the <br /> area extracted and the areas where pillars will <br /> be left in place. <br /> 3. The gradient and dip direction of the coal seam <br /> or, alternatively, a digitized grid of elevations <br /> on the top of the coal seam. <br /> 4. A digitized grid of surface elevations at each <br /> grid point. <br /> 5. The seam thickness. <br /> Analysis was performed using a computer code developed by Kenneth Myers for <br /> implementing the basic analytical procedures described by Marr, 1975. Subsidence <br /> values are calculated for each grid interval position within the defined surface <br /> grid area. Magnitude of subsidence as well as initial and final surface <br /> elevations are ccruted. Final results relative to surface elevations were found <br /> to be of little value in this extremely steep terrain. Therefore, all subsidence <br /> analyses in this report are depicted in terms of subsidence magnitude. <br />