Monitoring Excavation-Induced Deformation of a Secant Pile Wall Using Distributed Fiber Optic Sensors

Area of Science:

• Geotechnical Engineering
• Structural Health Monitoring
• Optical Sensing Technologies

Background:

• Large-scale bored pile walls are critical infrastructure components requiring robust monitoring.
• Traditional monitoring methods may not capture the complex thermal and strain behaviors during construction.
• Distributed fiber optic sensors (DFOSs) offer a potential solution for comprehensive pile wall monitoring.

Purpose of the Study:

• To investigate the application of BOTDA technology with DFOSs for monitoring a large-scale bored pile wall.
• To analyze temperature and strain variations during cement grouting, hardening, and excavation.
• To assess the accuracy of analytical methods in predicting lateral pile displacement.

Main Methods:

• Deployment of DFOSs for real-time temperature and strain measurement.
• Monitoring of a secant pile wall under field conditions, including geological assessment and installation details.
• Application of Numerical Integration Method (NIM) and Finite Difference Method (FDM) for displacement calculation.

Main Results:

• Significant temperature increase (~69 °C) and strain decrease (~0.5%) observed during cement hydration and shrinkage.
• Minimal temperature fluctuations during excavation, but significant strain distribution influenced by excavation depth.
• Calculated lateral pile displacement was minimal, consistent with the secant pile wall's high stiffness.

Conclusions:

• BOTDA technology combined with DFOSs is highly effective for monitoring complex behaviors of bored pile walls.
• The study validates the performance of NIM and FDM in analyzing strain data for displacement prediction.
• Findings confirm the structural integrity and minimal deformation of the monitored secant pile wall.