DETAILED GEOLOGIC MAPPING: AN ESSENTIAL STEP IN FOUNDATION DESIGN FOR SINKHOLE SITES

An interstate highway widening project in southeastern Pennsylvania intersected a complicated karst setting. Preliminary explorations revealed rock types not among the published information. Detailed geologic mapping conducted for the entire project identified many uncharted local faults and geologic structure. This information, combined with local geologic history and extensive explorations for various highway and bridge structures yielded an understanding of the various rock types and significant insight into sinkhole risk. As a result, a site-specific geologic map was developed tying together all of the various geologic factors, measurements and observations. The map served as a master plan throughout the design process, explaining the existence as well as absence of sinkholes in certain areas, and leading to sound and economical foundation systems in various difficult karst conditions.