Coal Mine Subsidence Below Streets, Highways and Public Buildings: A Special Concern for Southwest Indiana

摘要

Homeowners in Indiana can purchase insurance to protect their property from subsidence that occurs when older coal mines collapse. However, such insurance is not available to federal, state, county, and city governments when collapse under highways and structures occurs. Fortunately, the Abandoned Mine Lands (AML) section, Division of Reclamation, Indiana Department of Natural Resources, has a mitigation program to resolve some of these occurrences. Under the AML program, coal mining conducted before the 1977 Surface Mining Act took effect, is eligible for funding support. The AML program traditionally supports the reclamation of old strip mining areas, consisting of rows of cast over mine spoil piles, tailings ponds, steep final cut high walls, and gob piles of coarse material separated from the coal during the final operation. Within the last several years, the AML program has been extended to take care of subsidence below roads and structures of government entities. To date 14 projects have been completed under highways, bridges, an airport and a school building. Only mining operations conducted prior to 1977 are eligible for treatment, but later mines appear to be less susceptible to subsidence. Different techniques have been used in the past to stabilize room and pillar mines such as the use of grout columns. A different approach has been found to be more effective in Indiana, consisting of filling the entire opening with cement grout. The selection of projects, exploration, completion of the grouting operations and verification of success for several of the 14 projects is provided in the full paper.