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

PPT Presentation

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Advanced Continuous Surface Wave Testing (ACSW), developed by Ground Stiffness Surveys LLC, is a portable, non-intrusive method for profiling ground stiffness. A vibrating shaker generates Rayleigh waves, which six surface geophones record across a short linear array. By measuring wave speeds over a range of frequencies, ACSW estimates stiffness with depth: higher frequencies primarily reflect shallow ground, while lower frequencies provide information from greater depths.<br /><br />Each test takes about 20 minutes and can be conducted on surfaces such as concrete or asphalt. The method avoids boreholes, minimizes utility risks and site disturbance, and enables rapid assessment of lateral ground variability. It produces a representative stiffness profile, typically to around 30 feet, and measures stiffness at small strain. Results can be adjusted using strain-softening relationships to estimate design stiffness at a specified strain.<br /><br />ACSW converts Rayleigh-wave velocity to shear-wave velocity, then to small-strain shear modulus and Young’s modulus. The calculations use assumptions for Poisson’s ratio and soil density, which users can modify. Strain-softening adjustments may not apply to rock or certain problematic soils, such as peat or collapsible ground. Automated checks assess data quality and equipment calibration.<br /><br />The presentation identifies ACSW’s main uses as improving settlement analyses for foundations and embankments, supporting value engineering, supplementing ground profiles where stiffness contrasts matter, validating ground improvement, and estimating shallow shear-wave velocity for applications such as seismic design, liquefaction assessment, excavatability, and rock-quality evaluation. Examples include work at utility-constrained sites, forensic investigations, and assessment of fill thickness at a closed landfill.

Keywords

Advanced Continuous Surface Wave Testing

ACSW

ground stiffness profiling

Rayleigh waves

surface geophones

shear-wave velocity

small-strain shear modulus

non-intrusive testing

settlement analysis

liquefaction assessment