GEOPHYSICAL INVESTIGATION OF NEAR-SURFACE FRACTURES AND CONDUITS IN A THINLY MANTLED KARST SETTING; A CONCERN FOR THE US-60/160 INTERCHANGE IN SPRINGFIELD, MISSOURI

Springfield, Missouri is located on the Springfield Plateau which consists of thinly mantled carbonate and siliceous rocks. In Springfield, the uppermost exposed unit is the Burlington Limestone, a horizontal carbonate layer which is susceptible to karstification. Due to this susceptibility, the region within and around Springfield is prone to karst engineering hazards from caves and sinkholes. The Burlington Limestone is also a heavily fractured rock unit. These fractures have the potential to enlarge due to ground water flow and develop karst conduits. Therefore, an understanding of fracture location and orientation within the karst aquifer is an important factor in fully understanding the behavior and hazards associated with it.

The fractures within and around Springfield have been indentified from aerial photolineaments. Previous dye tracing investigations have correlated photolineaments at this site with dye trace paths and therefore potential karst conduits. An investigation of the photolineaments will be performed at the US-60/160 interchange on the south side of Springfield. Several photolineaments have been mapped in the vicinity of this intersection and typical fracture sets would suggest that some fractures extend beneath the interchange. Geophysical methods including electrical resistivity, VLF-EM and ground penetrating radar will be used to locate detectable fractures along the photolineaments. Where these fractures can be attributed to the photolineaments the investigation will further determine whether the fractures are in fact continuous underneath the interchange and therefore an engineering concern.