High-frequency radar evaluation of grouting integrity in HDPE-lined steel culverts

초록

Culvert slip lining restores deteriorated culverts by inserting a smaller-diameter HDPE liner and filling the annular space with grout to reestablish structural integrity. However, incomplete grouting can create voids that compromise load transfer and long-term performance. Existing inspection techniques provide limited or localized information, underscoring the need for a reliable non-destructive method to assess grouting integrity. This study investigates the use of high-frequency ground-penetrating radar (GPR) - operating up to 6 GHz- for detecting and quantifying voids within grouted annular spaces of lined culverts. The approach represents one of the first applications of high-resolution radar for this purpose and examines characteristic signal features such as amplitude attenuation, phase variation, and reflection signals, which are sensitive to discontinuities and material interfaces. Validation was achieved through a combination of numerical simulations, controlled laboratory experiments, and in-situ field measurements on rehabilitated culverts. Results from all three stages demonstrate that high-frequency GPR offers a reliable, non-destructive means to detect and characterize voids in culvert grout, enabling improved quality control, structural assessment, and maintenance planning. Voids identified by GPR in field trials were independently confirmed through endoscopic inspections.

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