Seismic anisotropy analysis across a vertical crack in concrete using a controllable high-frequency source

Document Type

Article

Publication Date

5-2026

Department

Department of Geological and Mining Engineering and Sciences

Abstract

The reliable detection of internal defects in concrete structures remains challenging in nondestructive testing (NDT). Conventional seismic sources, such as hammers or weight drops, lack repeatability and cannot generate sufficiently high frequencies for detailed defect characterization. This research addresses these issues by developing the Seesaw Hammer, a repeatable seismic source capable of generating controlled high-frequency seismic waves. Lab experiments verified its repeatability and frequency tunability by varying tip weight and stiffness, where lighter and stiffer tips produced higher frequencies. Thus, it is suitable for guided wave analysis in concrete structures. The Seesaw Hammer was tested on a concrete slab containing a vertical crack, using two configurations: parallel and perpendicular arrays relative to the crack orientation. Data was acquired for crack filled with air, water, and polyethylene glycol (PEG), a customized viscous fluid. Phase velocity and quality factor (Q-factor) analysis shows perpendicular array configuration resulting in lower Q-factor and phase velocity. The degree of seismic anisotropy (dependence of seismic properties on array orientation relative to the crack) varied significantly with fluid type. Air-filled cracks exhibited the highest anisotropy and lowest Q-factor, whereas PEG-filled cracks demonstrated the lowest anisotropy and highest Q-factor, indicating that seismic anisotropy analysis using the developed high-frequency seismic source effectively identifies and characterizes vertical cracks, as well as the fluids contained within them.

Publication Title

NDT and E International

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