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a = .013 <br /> b = .045 <br /> c = .109 <br /> d = .219 <br /> e = .259 <br /> f = .199 <br /> g = .056 <br /> Although applicable W lcngwall in U.K. minas, application of this method using <br /> the influence constant and zone factors given above was found to produce <br /> extremely conservative results in terms of subsidence magnitude and extremely <br /> non-conservative results in terms of horizontal ground strain when applied to <br /> mines in the United States. <br /> Subsequent investigators using data collected from U.S. mines have proposed <br /> modifications to the method which involved calculating a new influence constant <br /> and new zone factors for application to U.S. coal fields. In particular, Karmis, <br /> et. al., 1982, published data on the use of the zone area method for mining <br /> subsidence prediction in the Appalachian coal fields. Some of the more <br /> significant differences that they felt existed between U.S. applications and U.K. <br /> applications concerned the maxim m subsidence factor, the angle of draw, and the <br /> location of the inflection point as it controls the shape of the subsidence <br /> trough. Whereas in the U.K. the maxiimim subsidence factor for supercritical <br /> panels was proposed as 0.9, they felt a more appropriate factor for the <br /> Appalachian coal fields would be 0.5. Mean angle of draw in supercritical panels <br /> in the U.K. is considered to be 35 degrees whereas in the Appalachian coal fields <br /> they felt the angle of draw should be more on the order of 28 degrees. They <br /> further felt that the inflection point was displaced further towards the center <br /> of the panel and the resulting subsidence trough was somewhat steeper with a more <br /> i <br />