MASW Survey Identifies Causes of Sink Activity along I-476 (Blue Route), Montgomery County, Pennsylvania

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by R. Lee, Quantum Geophysics, 29 Richard Lee Lane, Phoenixville, PA 19460,,
P. Callahan, PennDOT District 6-0, 7000 Geerdes Blvd., King of Prussia, PA 19406-1525,,
B. Shelly, AECOM USA, Inc., 260 S. Broad Street, Philadelphia, PA 19102,,
A. Iqbal, Applied GeoSciences and Engineering, 1300 Holland Rd., 105, Reading, PA 19607, ayub_,
G. Kribbs, Aeon Geosciences, Inc., 2120 Bellemeade Ave, Suite 14-2, Havertown, PA 19083-2250,,

Document Type: Proceeding Paper

Part of: GeoFlorida 2010: Advances in Analysis, Modeling & Design

Abstract: The section of I-476 (Blue Route) between the Schuylkill Expressway (I-76) and the Mid-County Turnpike Interchange (I-276), Montgomery County, PA has a history of sinkhole activity. Where traditional drilling (unguided by geophysics) and a 2-D ERI (electrical resistivity imaging) survey proved partly effective, a MASW (multi-channel analysis of surface waves) survey linked a majority of sink activity (44 out of 52 reported sinkholes) to geologic conditions that included: enhanced weathering, the transition from shallow, competent rock to enhanced weathered rock, pinnacled rock, a potential fault or fracture, and potential voids. All of these features are expressed as differences in shear wave velocities (measure of material stiffness). The MASW survey was conducted in the southbound inside lane of the reinforced concrete roadway over the course of 3 nights, working between 10:00 P.M. and 5:30 A.M., averaging approximately 244 meters (800 feet) of continuous data per night. The process is documented in a 5-minute video (oral presentation only). The MASW survey explored to a depth of approximately 24 meters (80 feet) below grade, a difficult or impossible task by other geophysical profiling methods.

Subject Headings: Geomatic surveys | Highways and roads | Geophysical surveys | Rocks | Surface waves | Shear waves | Sinkholes | Two-dimensional analysis | Geological surveys | Pennsylvania | North America | United States

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