Geotechnical and Sink Holes
Underground Mine Subsidence And Sinkholes
Extraction of minerals by underground mining occurs in many areas of the country. There are also many areas where rocks that are soluble in water create cavities. Any opening in the ground has the potential to settle or collapse. Predicting when this will occur is speculative; it may happen within weeks or it may take centuries. However, by far the most common collapse or settlement is from underground mining.
No matter what the cause, collapse or settlement of the ground changes the contour of the surface from its original condition. Drainage patterns are altered, and damage to structures ranges from catastrophic to minimal. Subsidence, whether from underground mining or sinkhole collapse, can be a one-time event, but can continue for years in the same location.
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Donan Engineering’s beginnings were in areas of extensive underground coal mining with subsequent subsidence of the surface. Studies of underground mine subsidence was one of the first forensic projects made by the firm and continues to this day. Clients include affected homeowners, mining companies, and the federal government. Many states now require insurance companies to offer homeowners underground mine subsidence insurance in areas known to have underground mining.
Age of the old works is no predictor of the beginning of underground mine subsidence. Some of the old mines are now over 100 years old and are just now beginning to subside. In other cases, subsidence can occur within days of extraction.
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Settlements from the early stages of mine subsidence are often similar to settlements from other causes such as foundation and structural failures. The professional geologists and engineers with Donan Engineering have the experience to study the strata over the old works and the structure itself to determine whether or not mine subsidence has occurred.
Studies typically involve locating old mine maps, core drilling the strata over the old works, and examining the rock cores for signs of collapse. Studies of structures typically involve a survey of the floors to determine the slopes and amount of settlement, as well as to generate a detailed analysis of the structure to eliminate other causes of distress. Studies of structures subsiding from naturally occurring sinkholes are similar.
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Since subsidence can be an on-going event at the same location, it becomes necessary to determine when it has ceased. Repairs should not be made to a structure built on ground that is still moving. Donan Engineering’s professional staff has the equipment and expertise to monitor structures and the ground to determine whether or not subsidence has stopped. This prevents needless expense by the affected parties.
Donan Engineering Company’s experience in this highly specialized field is unique. The combination of professional geologists and professional engineers allows us to determine whether or not problems with a structure are due to underground mine subsidence, a naturally occurring sinkhole, or an otherwise unrelated condition.
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