The current study is part of the U.S. Department of Energy's (DOE) on-going subsidence research program. The long-term objective of the DOE program is to develop analytical methods of subsidence prediction applicable over a broad range of geologic and mining conditions encountered in the United States. The DOE currently bas several contracts in progress to develop a sound data base that can be used in the development of predictive models. Dames & Moore is currently under contract to DOE to collect and analyze detailed subsidence and hydrologic data from a coal mine employing longwall mining methods in the Eastern Coal Province. Work under Contract No. DE-AC22-80PC 30335 began in October of 1980 and will continue through September of 1984. The contract includes monitoring of two adjacent longwall panels. This paper summarizes the surface monitoring work that was performed through February of 1982. Mining of the first of the two panels (3 off 3 north) was completed on February 3, 1982. Results of the surface monitoring through completion of this panel are presented and discussed.
The mine being studied is located in eastern Ohio. The site is west of the Ohio River, approximately 56 km (35 miles) south of Wheeling, West Virginia. The topography of the unglaciated region is characterized by closely spaced valleys situated between steep, narrow ridges. Depth of cover in the study area ranges from approximately 102 m (310 feet) to 249 m (760 feet) above the coal, which is at an elevation of 161 m (490 feet) above mean sea level (MSL). Two longwall panels are being studied, each approximately 1640 m (5000 feet) long by 157 m (480 feet) wide. The geologic strata of the study area are composed of interbedded shale, siltstone, sandstone, and limestone units primarily from the Greene, Washington, and Monongahela formations of Permian and Pennsylvanian age. The mine is producing from the Pittsburgh No. 8 seam. The Pittsburgh No. 8 seam at the project site is 1.6 m (4.95 feet) thick and is overlain by 0.6 m (1.85 feet) of roof coal with interbedded shale. Mined thickness ranges from 2.3 m (85 inches) to 2.4 m (88 inches). The two panels selected for study, PANEL 3 OFF 3 NORTH and PANEL 4 OFF 3 NORTH, are shown in relation to surface topography on Figure 1. The mine employs a retreat longwall mining method. The direction of mining is from east to west. The panel sequence is from south to north. The panel directly to the south of PANEL 3 OFF 3 NORTH had been mined prior to the start of the current project.
Surface instrumentation includes the installation of 338 surface monuments and the installation of full-profile borehole inclinometers (FPBI) and extensometers (PFBX) in two boreholes at the locations shown on Figure 1. Installation of all surface monuments has been completed. In addition, the ADAS will be installed at the four locations over panel 4 OFF 3 NORTH, also shown on Figure 1.