GIS-Based Spatial Analysis Coupled with Geophysical Imaging to Identify and Evaluate Factors that Control the Formation of Karst Sinkholes in Southwestern Missouri

摘要

Sinkholes are inherent features of the karst terrain underlying much of Greene County, Missouri. These features present hazards and engineering challenges to existing infrastructure unknowingly constructed on a seemingly benign ground surface. The primary objective of this research was to investigate the physical processes chiefly responsible for triggering the seemingly random distribution of sinkholes in the study area. This research employed an integrated approach encompassing regional scale GIS-based spatial analyses and site-specific geophysical data. GIS-based spatial analysis was employed to identify significant physical factors that appeared to influence the formation and distribution of sinkholes. Seven out of the twelve most cited factors influencing sinkhole development were identified in the study area. These factors were: overburden thickness, depth-to-groundwater, slope of the ground surface, distance to the nearest water course, distance to the nearest geologic structures, distance to nearest springs, and distance to the nearest roads. In the site-specific geophysical investigations, two dimensional (2D) and pseudo three dimensional (3D) - ERT, MASW, and borehole data were used to characterize the subsurface morphology of the karstified soil-bedrock interface in five selected sinkholes. From the interpretation of the 2D and pseudo 3D-ERT profiles, it was determined that four of the five sinkholes occurred at the intersections of regional systematic joint sets. The joint sets are characterized by a linear, visually prominent zones of low resistivity. The relatively low resistivity values are attributed to vertical seepage and the associated piping of fine-grained soils through preexisting fractures (often widened by solutioning).