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GROUND CONTROL S]'STE`+ <br />F07. RIENAU ll2 TUNE - 2nd EAST SECTION <br />• <br />The purpose of this study is to determine to what <br />extent, if any, disturbance will occur to the surface and <br />overlying strata as the 2nd East Section of Rienau fl2 Mine <br />advances under Curtis Creek. <br />A conservative, or worse case, approach is taken <br />in that maximum pressures and minimum strengths are used in <br />the calculations. <br />The pillars under the area to be protected are 130 <br />feet by 60 feet solid coal on 150 feet by 80 feet centers. <br />This is 63:C larger than the standard pillars used in the <br />Rienau 02 Mine. The mining heighth averages between 8 to <br />10 feet. <br />The width of the possible AVF {alluvial valley floor) <br />is estimated at 30 feet with Curtis Creek establishing the <br />approximate center line of [he possible AVF. An additional <br />safety strip of 50 feet is added to each side of [he possible <br />AVF. Therefore, the total width of surface to be protected is <br />130 feet. (Figure A) The lateral north-south width is not <br />considered due to the virgin coal to the north and the barrier <br />• pillar to the south which will be addressed later in this report. <br />Due to the protection of the solid coal to the North and South, <br />if subsidence were to occur, it would be in the center of the <br />2nd East Entry System. Therefore, the thickness of our burden <br />at the east-west edges of the protected surface area in the <br />center of the Zad East Entries is used to calculate the angle <br />of dray width. This thickness is found to be 480 feet. <br />(Figure B) Using a conservative angle of draw of 30o the <br />width (W) of the draw area is calculated: <br />W = 480 ft. X tan 30° = 277 ft. <br />W = 280 f t . <br />Therefore, 280 feet are added to east-west sides of the pro- <br />tected surface area. Thus, the total width of the protected <br />area at the G seam elevation is = 280 ft. + 50 ft. + 30 ft. + <br />50 ft. + 280 ft. = 690 feet. <br />The maximum overburden to be supported within the <br />protected length is found to be on the east and west side of <br />the 690 feet length at points A and A~. (Figure B) This <br />depth is S50 feet. Using the standard of l.lpsi per foot of <br />overburdenl and correcting for difference in pillar area and <br /> <br />5?:E Mining Engineering Handbook, Vol. 1, pg. 13-37 <br /> <br />