Deep-mine voids are an insidious hazard and early identification is imperative to minimizing subsidence to roads, bridges, buildings and other infrastructures. Continuous vertical electrical sounding (CVES) can be a rapid and effective tool for the detection of deep-mine voids; however, there are inherent issues with CVES including cultural noise, surface mining, and anomalous lithology. CVES imaging of a recently exposed limestone cave in State College, Pennsylvania documents the usefulness of CVES for the detection of subsurface anomalies.
Deep-mining for clay in St. Marys, Pennsylvania, an unusual and unexpected deep-mined rock type, proved to be a potentially hazardous threat to a proposed subdivision. The 7-meter thick sandstone overlying a 140-year old mine void in the Akron, Ohio area is slowly collapsing and subsidence may adversely impact roads and residences. CVES profiles indicated that subsidence may affect only 25 residences and that only 6 residences were exposed to immediate subsidence. A field in western Pennsylvania was cleared for the installation of a manufacturing facility; however, CVES showed that the building footprint overlapped a highwall and deep-mined workings. Borings showed that the highwall and deep-mine workings were present and the building was redesigned to accommodate the potential hazards from subsidence.
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