Abstract This study presents a field investigation on the behavior of cast-in-drilled-hole (CIDH) piles subjected to eccentric loading, incorporating distributed fiber optic sensing (DFOS) measurements, three-dimensional deformation analysis using the DFOS data with a shape sensing method, and finite-element-based inverse analysis. Four test piles with different post-grouting techniques were instrumented with DFOS to capture continuous strain distributions. The results indicated that even minor construction-induced eccentricities, within standard tolerance limits, can produce asymmetric strain profiles that are often undetectable using conventional sensors. A shape sensing method based on Cosserat rod theory was applied to evaluate three-dimensional pile deformations, revealing variable bending directions associated with eccentric loading. An inverse analysis framework was developed by integrating DFOS measurements with a finite element model that simulates coupled axial–lateral pile response with a nonlinear pile–soil interaction model. The framework is able to successfully estimate nonlinear soil reaction parameters and quantify both the magnitude and direction of eccentricity. The optimization results were validated against borehole verticality measurements and shape sensing outputs, confirming the model’s reliability. While the inclusion of eccentricity had a minor effect on the estimated load-transfer parameters, it was critical in identifying localized anomalies and explaining pile-specific responses. A comparative analysis using vibrating wire strain gauges (VWSGs) further highlighted the advantage of DFOS, since the limited spatial resolution of VWSGs led to unstable and unreliable inverse analysis results. The proposed DFOS- and finite element model (FEM)-based approach, complemented by shape sensing, provides a robust tool for evaluating pile performance under eccentric loading and offers high potential for improving reliability in geotechnical design and construction quality control.
Shin et al. (Tue,) studied this question.