Application of Electrical Resistivity Method in Steeply Dipping Karst Terrane

Electrical Resistivity profiles were acquired along three separate parallel traverses on a steeply dipping slope at a construction site near Kansas City, Missouri. The intent was to determine variable depth to bedrock and differentiate the interlayered limestones and shales. This information in conjunction with boring data was necessary for optimum location of a foundation. The determination of depth to bedrock along the electrical resistivity traverses was complicated by several factors. First, eleven different formally-defined lithologic units (alternating limestones and shales) subcrop along the length of the traverses, so the top of rock is not defined by a fairly-consistent resistivity contour-value. Additionally, the limestone units do not thin gradually. Rather, they terminate abruptly as undercut scarps. The differentiation and mapping of the various subsurface lithologic units was also complicated because of variable water saturation along the length of the traverses. As a result, each lithologic unit is characterized by a range in electrical resistivities that vary depending upon the degree of saturation. The interpreted electrical resistivity profiles correlate well with the three borings that were acquired on-site and depth to water table control.