A system for inspecting karst voids during construction of cast-in-place pile foundations

Abstract

Karst voids at pile locations are highly adverse to the bearing capacity and construction safety of cast-in-place pile foundations. This study developed an inspection system prototype of karst voids during cast-in-place pile foundation construction. The system consists of a multifrequency borehole sonic probe, two pile hole sonar probes, an in situ computer, and a corresponding signal analysis method. Borehole and pile hole detection are conducted during the investigation and pile hole drilling to inspect karst voids around the borehole and beneath the bottom of the pile hole. The analysis of the synthetic data verifies the effectiveness of the proposed method. A field inspection of karst voids during cast-in-place pile foundation construction was conducted. Comprehensive geophysical methods, including borehole optical imaging, 3D laser scanning, and borehole logging were deployed for comparison. The results show that the system can provide detailed geological information to the design of piles and ensure the construction safety of foundations.