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pronounced curvature at both top and bottom resulting in the larger horizontal <br /> ground strains typically observed in the U.S. fields. With regard to Appalachian <br /> coal field applications, Karmis, et. al. , proposed an influence constant of n = <br /> 3.61. He further proposed a series of zone factors a-g as follows starting with <br /> the innermost circle: <br /> a = 0.50 <br /> b = .144 <br /> c = .159 <br /> d = .188 <br /> e = .100 <br /> f = .034 <br /> g = .005 <br /> In recent years investigators have also been detecting differences within <br /> different regions of the United States. Available data on subsidence at western <br /> coal mines is very limited. However, we have collected what data we can find <br /> from our own files and from the files of the U.S. Bureau of Mines Research Center <br /> in Denver and plotted that data on the diagrams previously published by Rarmis, <br /> et. al., in 1982 (see Appendix B ) . Based on the limited amount of data <br /> available to date we see little difference in general between Appalachian coal <br /> fields and western coal fields with the exception of the maximum subsidence <br /> factor. Based upon my own experience and that of several colleagues, it is my <br /> opinion that the maximum subsidence factor for western coal fields should be on <br /> the order of 0.65 to 0.7 as opposed to the 0.5 reecmmended for use in Appalachian <br /> fields. Based on a best fit curve drawn through the data provided in Figure 7 of <br /> Appendix B, we have computed a new influence constant and set of zone factors a-g <br /> for application to western coal fields. Zhese are as follows: <br />