Multifaceted Approach for Evaluating and Treating Sinkhole Activity beneath Highways – Case Study: SR 0422 in Southeastern Pennsylvania

摘要

In the overnight hours between September 30th and October 1st, 2010, several sinkholesdeveloped along a heavily-traveled section of SR 0422 in southeast Pennsylvania. Inconjunction with PENNDOT’s geotechnical engineers, Gannett Fleming developed a sinkholeinvestigation program to identify the likely sources of the sinkhole activity amid the busyhighway environment. The sinkhole investigation program consisted of a multifaceted approachincorporating three different geophysical survey methods; test borings within the travel lanes,shoulders, and median; a comprehensive review of available geologic data, including previoustest borings performed adjacent to the investigation area; a visual pavement conditionassessment; and visual and survey monitoring of the ongoing sinkhole and subsidence relatedactivities across the site.The geology of the project site is characterized by a variable bedrock surface consisting ofpinnacles, solution cavities, fracture zones, and a localized thrust fault. Using a comprehensiveinvestigation approach allowed for the analysis and consolidation of a large amount of dataleading to a more detailed interpretation of the subsurface conditions. Based on the findings, alimited mobility grout program was designed and implemented to address the subsidencefeatures at the site and mitigate future sinkhole activity.Several logistical challenges were encountered during the investigation and subsequentconstruction phase of the project, including maintenance of traffic, limited work zone areas, andtime constraints. Sinkhole activity in the carbonate belt of southeastern Pennsylvania is notunfamiliar to engineers and geologists, however, when sinkholes occur in a heavily-traveledhighway corridor, they present unique challenges for investigation and remediation.