Surface Subsidence Due to Coal Mining in Illinois

134 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1980.Subsidence of the land surface has been associated with coal mining in Illinois since the early days of the industry. Investigations of subsidence damage began in Illinois more than 100 years ago. However, over the years there has been very little scientific or engineering documentation of subsidence movements in Illinois. In Europe on the other hand, knowledge of coal mine subsidence has progressed to a fairly advanced state, for longwall mining in particular.This investigation was primarily a field study of subsidence development in Illinois. Since there has been relatively little scientific or engineering work in this subject in Illinois, the three principal goals of the study were: (1) documentation of subsidence case histories in terms of the mode, magnitude, and areal distribution of vertical surface movements, (2) identification of geologic conditions and both old and new mining practices in Illinois, (3) characterization of the typical subsidence profiles for various methods of mining in Illinois.Previous investigations have either identified or demonstrated the influence certain mining and geologic factors have on the mode, magnitude, shape, and lateral extent of subsidence. The significance of these investigations lies in the observation that there are three fairly distinct phases in subsidence development; these phases operate at the mine workings, overburden, and ground surface and correspond to the initiation, transmission, and surface expression of the strata movement. At the level of the workings, the areal extent and amount of extraction control the character of any movement that may result from the failure of the roof, pillar, or floor. As the strata movements migrate upwards, they are modified by the character of the overburden. Both the quantity and quality of the soil and rock components have been identified as significant factors influencing the magnitude and areal extent of the subsidence movements. The final zone of the expression of subsidence occurs at the surface. The details of the surface expression such as location, width, and depth of cracks results from the surficial conditions including material properties, moisture content, and surface development. Topography and local hydrology largely control the extent and magnitude of horizontal and vertical movements near the surface.The general goal of this study was to identify the influence that both geologic conditions and mining practice may have on the character of subsidence in Illinois coal fields. This study has documented a number of subsidence case histories in terms of vertical subsidence movements. Although the variation of geologic conditions for these case histories has not been great, regional geologic control can be inferred from the results. The mining methods, on the other hand, range from room-and-pillar to longwall with extractions from 40 percent to 100 percent. Furthermore, the method of mining, reflecting the percentage of extraction as well as the type of support remaining, has been shown to be a predictable factor in subsidence analysis.Two general conclusions of this study are: (1) the percentage of extraction has a similar influence on subsidence profile development to that of panel width/mining depth (W/D) for longwall mining; and (2) specific regional differences in the profile development, such as between Illinois and England, can be attributed to a combined effect on rock mass properties and mining geometry (depth in particular).U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD