Charles B. Wheeler Airport
Owner/Client: Kansas City, Missouri Aviation Department
Location: Kansas City, Missouri
Geotechnology conducted geophysical services, including ground penetrating radar (GPR) and multichannel analysis of surface waves (MASW) surveys over a failed portion of a 42-inch corrugated metal pipe beneath a taxiway. The geophysical survey was sparked from video inspections of the pipe, demonstrating that sand and silt migrated into the pipe at the point of failure, creating a concern about voids forming beneath the active taxiway.
Geotechnology used a GSSI SIR 3000 GPR system with 400 MHz antenna. GPR data were collected along closely spaced parallel lines and processed as a 3D data block. Active mode MASW surveys were conducted using a Seistronix RAS 24 seismograph and 4.5 Hz geophones. Data were collected over the alignment of the subject sewer and perpendicular to the subject sewer at the suspected location of the failure. Profiles of seismic shear wave velocities were generated based on dispersion analysis of frequency curve picks. The one-dimensional inversion velocity models along the MASW line were combined and contoured to produce velocity profiles. A high amplitude, bowl-shaped GPR anomaly (suspected void) was observed immediately beneath the concrete over the expected pipe failure. This anomaly was observed in multiple depth slices of the 3D GPR data. The purpose of the MASW data was to extend the depth of the geophysical investigation beyond the limits of the GPR survey. Our MASW interpretation focused between depths of approximately 10 feet and 50 feet beneath the pavement surface. The MASW data indicated power velocity material in the vicinity of the suspected sewer failure, which may indicate the presence of voids or less consolidated soils.