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June 1992 Cyprus 7CC • Pradution ojSulndencc fJjcru ~ J <br />• 6. Development of subsidence contours in the Fish Creek AVF study area <br />corresponding to Panel 5 extraction and Panel S and 6 extraction using the <br />predicted profile data. <br />During the course of this work, we evaluated the use of the Virginia Polytechnic Institute (VPI) <br />Zone Area method (Karmis et al, 1987) for predicting subsidence at the site. Unfortumtely, the <br />program interrupted (error associated with calculation of the square root of a negative number) <br />during simulation of the six panel layout. Subsequent conversations with Dr. Michael Karmis <br />indicate that this method may not be suited to this project. In particular, the VPI Zone Area <br />model does not satisfactorily predict start and end subsidence profiles. <br />Dr Karmis recommended the use of the VPI Influence function method for the site based on <br />VPPs analysis of published Western U.S. case studies (York Canyon, Deer Creek)(Karmis, 1992), <br />and requested that we re-contact him regarding the results of this exercise and any future <br />problems with the code. <br />While the VPI influence function method may be appropriate for use in future mine planning, <br />it haz not been evaluated az pan of this study, az the input routine, requiring definition of edge <br />effects (.e., reloation of the inflexion point), does not cater for rubaitical conditions typial <br />of those existing at [he Foidel Creek mine (e.g., a width/dep[h (W/h) ratio of 0.58). <br />Funhermore, examination of Figure 3.3 of Volume 2 (Karmis et al ,1987) indiates that this <br />method haz been calibrated using case studies with W/h ratios of 0.75 and higher. Therefore, <br />predixions using this method are likely to result in over-estimation of subsidence displacements <br />• outside the panel ribs and over star and end regions of the coal face for panels considered in <br />this study. <br />3.0 ANALYSIS OF EXISTING MINE DATA <br />Subsidence rurvey data were retrieved from Twentymile Coal Company in the format shown <br />in Table 1. Typically, this data includes three dimensional coordinates for individual <br />monuments for a series of rurvey dates which represent conditions prior to undermining and <br />various stages of Panel completion. <br />The procedure used to reduce these data to subsidence, displacement and strain profile data waz <br />az 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 ®RlSIC attachment. <br />Step 2 -Survey data corresponding to required stages of Panel completion were grouped <br />and analyzed statistically to screen out rurvey errors. For example, with reference to <br />Table 2; <br />• Bazeline data were established for Survey Line 12000E by selecting a date prior <br />to the Panel start date of October, 1989. <br />. - Three xts of data corresponding [o the date criterion were selected for <br />each Monument <br />- The mean and standard deviation for each set of data were alculated <br />ACZ /ru. ' P.O. 80: 7740!8 ' Stwmbaat Spring; Colorado 80477 ' (J03J879-6260 <br />