Advanced Continuous Surface Wave Testing (ACSW): Geologic and Geotechnical Site Characterization for the 21st Century-Paper

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Advanced Continuous Surface Wave (ACSW) testing is a rapid, non-destructive method for profiling ground stiffness. It measures Rayleigh-wave velocities across a range of frequencies: shorter wavelengths reflect shallower layers, while longer wavelengths provide information from greater depths. These measurements are used to estimate shear-wave velocity and small-strain stiffness, which can then be adjusted to represent expected operational strains.<br /><br />The system described uses a portable mechanical vibrator, six geophones arranged across a 3 m array, and automated data acquisition and analysis software. A test takes less than ten minutes. The software checks data quality, produces velocity-depth profiles, and performs advanced inversion to estimate layered stiffness profiles. The authors report typical profiling depths of about 10 m and field productivity of three to four tests per hour.<br /><br />Direct stiffness measurements can improve settlement predictions compared with values inferred from SPT, CPT, or strength correlations, which may be uncertain and conservative. ACSW profiles can support foundation settlement analysis, detection of subsurface layers and changes in rockhead, earthwork and ground-improvement verification, working-platform assessments, rock-quality and rippability evaluations, void detection, and forensic investigations. Its portability and non-intrusive operation also make it useful around utilities, existing structures, railways, dams, and levees.<br /><br />The paper concludes that ACSW offers a practical way to obtain detailed in-situ stiffness data and has been shown to support realistic predictions of foundation performance.

Keywords

Advanced Continuous Surface Wave

ACSW

ground stiffness

Rayleigh-wave velocities

shear-wave velocity

non-destructive testing

geophones

velocity-depth profiles

foundation settlement analysis

in-situ stiffness data