The Linwood Mine is an underground limestone mine at Buffalo, Scott County, Iowa that operates on two levels. The limestone rock units exposed at Linwood underwent a period of dissolution by ground water (karstification), forming cavities controlled by pre-existing weaknesses in the rock. Many of these cavities subsequently filled with stream sediment. Large sediment-filled cavities have become a safety concern for the mining company because they are prone to collapse, leading to dangerous situations for mine workers as well as for operations at the surface. The purpose of this project was to provide the company with information leading to prediction of where these cavities might exist in unmined areas so that areas of high risk might be avoided.
In an attempt to define areas of high cavity concentration and areal patterns of cavity distribution, a Geographic Information Systems (GIS) program was utilized. This technology, which had not been used in previous studies of the mine, made it possible to combine data from past projects quickly and to show them together with the new data in graphic form. Analysis of combined attribute maps such as cavity distribution and stream drainage allowed specific areas of concern to be located more precisely and seen more clearly.
Past studies of paleokarst in the mine include areas from both levels. This particular study deals with the past research in addition to a focus on a previously unmapped portion of the eastern Davenport level. Areal cavity distributions that were shown by previous studies were confirmed and expanded with the addition of the eastern Davenport area data. Differences in individual cavity control between the upper and lower levels of the mine were also seen, with those in the Davenport level controlled by high-angle fractures, and those in the lower (Otis) level controlled more by bedding planes. As more data are collected in this long-term project, large-scale patterns of cavity distribution that would help guide Linwood mining operations may eventually be revealed.
Jacob S. Benner, ’97
Sponsor: Paul Garvin