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<br />7 <br />1 . II~'I'IiCWCfION <br />Vertical subsidence and horizontal strain predictions in gen- <br />erally flat coal warts are rtede using the method developed by the <br />British National Coal Board (NCB). In the Subsidence flxlineer's <br />Handbook published in 1975 by NCB, convenient nomograms are pro- <br />vided to facilitate designs of stable pillars in areas where a <br />minimum subsidence is permited. <br />In inclined and steep-laying sears, the angle of draw at thc• <br />lower face becanes flatter with increasing dip, whereas the angle at <br />the upper face beLrn~es steeper. The angles deperd on the lithologi- <br />• cal crn~position of the strata. The subsidence trough above steep <br />seams is always asymmetrical. The curve of tension and compression <br />derived from the subsidence line has a tension peak over the lower <br />unmmined seam, and a strong ornipression peak over the upper half of <br />the mined-out area, In a very steep seam, there is practically oT~ly <br />one tension peak and one compression peak. <br />In the literature, the position of the subsidence trough centre <br />is often given as being over the upper half of the mined- wt area, <br />sanetimes over the lower part. Both cases are practically possible, <br />depend.~ng cn the dip, depth, thickness of the seam, arr3 the dimen- <br />sions of the opening. <br />In this report, the subsidence trough calculation has been made <br />• in agreement with the Handbook. The rtsximimi subs3ct~n~ has beef <br />