CORVETTES AND KARST: A MICROGRAVITY SURVEY AT THE NATIONAL CORVETTE MUSEUM, BOWLING GREEN, KENTUCKY

On February 12, 2014, eight classic Corvettes were swallowed by a sinkhole collapse that opened up beneath the Skydome of the National Corvette Museum in Bowling Green, Kentucky. The museum—a non-profit organization that provides a firsthand experience to learn the history and design of the Chevrolet Corvette—estimated the cost of damage in the millions of dollars. The incident garnered national media attention, bolstered by dramatic security camera footage showing the Corvettes dropping into the void.

Complicating the recovery and repair effort was the fact that the vertical and lateral extent of the subsurface void was unknown. EnSafe aided in this effort by designing and conducting a geophysical survey utilizing a Scintrex CG-5 Autograv Microgravity Meter. Due to the sensitivity of the gravimeter, data collection was conducted at night when construction equipment associated with the Skydome stabilization and restoration was not in operation.

Microgravity methods measure lateral variations in the density of the earth’s subsurface and can be used to infer potential voids, cavities, and depth to bedrock or other significant variations in composition. Higher than normal variations in gravitational force indicate relatively denser underlying material while lower than normal gravitational variation suggests lower density subsurface composition.

Subsequent to completion of the plan-view microgravity map, a team of experienced EnSafe and Western Kentucky University cave surveyors entered the collapse and prepared a cave map consisting of cross-section, profile, and plan views. The microgravity map was overlain on the plan-view cave map, revealing excellent correlation between the void orientation inferred from the microgravity data and the actual cave dimensions. Ultimately, the National Corvette Museum collapse was evaluated using three investigative methods implemented sequentially: water hammer drilling (during micropile installation for structural stabilization), a microgravity survey, and cave mapping, with data from the complementary methods used in remedial planning and engineering design.