Subsidence-induced deformation and hydrologic changes were studied at two active longwall coal mines in Illinois using surveying and geotechnical monitoring. Surface subsidence characteristics fall into a range common to other Illinois longwall operations. Subsidence-induced water level fluctuations correlated with mining activity and the passing of the dynamic subsidence wave. Aquifer thickness and lateral extent affect these fluctuations. Bedrock water levels completely recovered at site 1 and partially recovered at site 2. Comparison of pre-and post-subsidence logs showed increased fracture frequency and decreased seismic velocities in the overburden at site 1. Deformation monitoring at site 2 showed only small vertical differential displacements within the overburden, suggesting a nearly uniform drop of the subsided rock mass and a caved zone extending less than 6 m above the mine. Mechanisms of overburden deformation observed at both sites include bedding separations and shear within incompetent formations.
Additional publication details
Overburden deformation and hydrologic changes due to longwall coal mine subsidence on the Illinois Basin
Publ by Int Assoc of Hydrological Sciences
Wallingford, United Kingdom
Larger Work Title:
IAHS Publication (International Association of Hydrological Sciences)
Proceedings of the 4th International Symposium on Land Subsidence