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SubTerra, Inc. CYVCC-Foidel Creek Mine-Subsidence :. -- March 23,1993 <br />i <br />• 1.3 Analysis of Existing Mine Data <br />Subsidence survey data were retrieved from Twentymile Coal Company in the format shown in <br />Table 'l. Typically, this data includes three dimensional coordinates for individual monuments <br />for a series of survey dates which represent conditions prior to undermining and various stages <br />of Panel completion. <br />The procedure used to reduce these data to subsidence, displacement and strain profile data was <br />as follows: <br />Step 1. Individual monument data (e.g., see Table 1) were input to a Lotus 1-2-3 <br />spreadsheet incorporating the Palisades @RISK attachment. <br />Step 2. Survey data corresponding to required stages of Panel completion were <br />grouped and analyzed statistically to screen out survey errors. For <br />example, with reference to Table 2; <br />Baseline data were established for Survey Line 12000E by selecting <br />a date prior to the Panel start date of October, 1984. <br />Three sets of data corresponding to the date criterion were <br />selected for each Monument. <br />- The mean and standard deviation for each set of data were <br />calculated. <br />- The mean value was used in the subsidence calculations <br />while the standard deviation was utilized to estimate <br />possible inaccuracies in the analysis. <br />o Survey data, corresponding to the mining of Panel No.l at least full <br />depth past the survey line, were selected and analyzed to produce <br />Monument coordinates for Panel No.l's subsidence, displacement, <br />and strain profiles. <br />o One set of survey data, corresponding to the mining of Panel No.2 <br />at least full depth past the survey line, was selected to produce <br />Monument coordinates for Panel No.2's impact on Panel No.l's <br />subsidence, displacement, and strain profiles. <br />Survey data, corresponding to the mining of Panel No.3 at least full <br />depth past the survey line, were selected and analyzed to produce <br />Monument coordinates for Panel No.3's impact on Panel No.l's <br />subsidence, displacement, and strain profiles. <br />Step 3. Subsidence, slope, curvature, horizontal displacement, and strain were <br />computed, tabulated, and plotted for each survey line using the Monument <br />coordinate data calculated in step 2. <br />• <br />