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3ta SUalAC6 SUIiSIDENCtt <br />ORINGINAL 9UgfACE LEVEL • <br />i <br />`I '• a <br />•\. I v v I / <br />f.OAf BEAM <br />LEGEND <br />E~aUa81DENCE •: EaTEJ1alON <br />a~8UB91DENCE AT ~:tbNTfUICTION <br />aOTTOM f; laaT ANCLE <br />V:OISPLAC EMENT <br />~ fA.t HoriaonW And vertieAl componeNa of ywnd movement (a). Couruuy U. K. <br />NuboJ Coe( Dowd. <br />A graphical method of predicting the complete subsidence profile was <br />developed by the U.K. National Coal Board (12) based on a large number <br />of field observations. For example, the subsidence profile for a longwall <br />face w meters wide in n seam nl meters (hick ut u depth of /~ meters below <br />the surface can be determined from Fig. 9.1.2 as follows: <br />For w ~ 160, h ~ 400, and m ~ 1.4, <br />' Slnt ~ 0.37 `. <br />S ~ U.37m <br />0.37 x 1.1 <br />0.518 (m) <br />where S is the maximum aubsidcntc, directly above the center of Iho <br />upL;ning.'fhu de[crminuliun of the subsidence profile is best carried out in <br />a table Gke Table 9.4.1. Row I in the table lists steps of ratio of local <br />subsiJcncc to maximum subsidcncc (s/.Y) Nctwcon 0 fur the subsidcnw <br />ulge and 1 fur the center point. The number and interval of steps arc <br />arbitrary. Multiply each step in row 1 by.S ~ O.S 18 l0 Ub1711n r11W 2; hx:+Uc <br />diuwlu: value dlh (whi.rc d is distance from the center of the paneU [or <br />wlh ~ 0.4 from Table 9.4.2 for row 3; then multiply values in row 3 by h <br />400 to obtain the sews( distance from the center of the panel for row 4. <br />Row 2 lists actual subsidences for points listed in corresponding columns <br />of row 1. The final subsidence profile is plotted in Fig. 9.4.3. The subsi- <br />dence profde predicted by this method usuaAy wmea within t 103b of the <br />actual field measurements. <br />L <br />