2008-01-16_APPLICATION CORRESPONDENCE - C2008086 (3)

Home Browse Search

DRAFT Measurements 9.0 SURFACE SUBSIDENCE MONITORING Various governmental bodies may require a monitoring demonstration that the predicted subsidence effects are indeed conservative and not significantly exceeded. Specifically, a monitoring program over one of the initial longwall panels that will obtain subsidence data on the maximum vertical subsidence (Smax), tensile (+E) and compressive (-E) horizontal strains, angle of draw (a) and subsidence induced tilt (G) for this unique geologic environment. If room-and-pillar panels are mined it may be necessary to measure the same subsidence effects, or to demonstrate that sufficient pillars are left to prevent subsidence. The Surface Subsidence Monitoring Guidelines by Abel (1982) indicate one possible monitoring program that has been utilized to provide the data, when required. Figure 21. Subsidence Monitoring Program indicates the location of surface monuments for flat lying terrain. The rugged terrain and rapidly changing overburden depth in the Project Area will necessitate panel-by-panel monument spacing modifications in the field after the locations of the initial panels become available. Either monument spacing for the test panel will have to be continuously changed to match overburden changes or all monuments will have to be spaced to match the shallowest overburden for that panel. Considerable advances have been made since the early subsidence transit and leveling monitoring programs by the NCB. The precise leveling used by Collins (1977), has been replaced by Electronic Distance Measurement (EDM) and more recently the Global Positioning System (GPS) has apparently increased its accuracy to the point that it has been used to measure subsidence induced changes at the ground surface. There is no substitute for properly constructed monuments either anchored to bedrock or at sufficient depth to prevent temperature and moisture changes from impacting the . measurements. 10.0 REFERENCES Abel, Jr., J.F., 1982, Surface Subsidence Monitoring Guidelines, Phase 1 Report: U.S. Geol. Survey Contract No. 14-08-001-18822, 11 p. Abel, Jr., J.F. & F.T. Lee, 1984, Lithologic Controls on Subsidence: Trans. SME/AIME, v 274, p 2028-2034. Abel, Jr., J.F., 1988, Soft rock pillar design: Intl. Jour Mining & Geological Engrg, v 6, p 215-248 Bauer, R.A., B.B. Mehnert, D.J. van Roosendaal, P.J. DeMaris, N. Kawamura & C.J. Booth, 1995, Land subsidence and hydrologic changes due to longwall coal mining in Illinois: in Land Subsidence Case Studies and Current Research, AEG Sp Pub 8, p 218-228. Booth, C.J. and E.D. Spande, 1992, Potentiometric and aquifer property changes above subsiding longwall min panels: Ground Water, v. 30, no. 3, May-June, p. 362-368. Brauner, G., 1973:, Ground movements and mining damage, Pt. 2 of Subsidence due to underground mining: U.S. Bureau of Mines Information Circular 8572, 53 p. Page 44 of 57