Automated monitoring of deep excavations using fiber bragg grating technology

This study presents an integrated automated monitoring system for foundation pits based on fiber Bragg grating (FBG) technology. The system enables real-time measurement of diaphragm wall horizontal displacement, internal forces in supports, differential settlement of concrete struts, soil heave at the excavation base, and lateral earth pressure, facilitating comprehensive evaluation of deformation and safety. The field results indicate that the data from the automatic fiber inclinometer aligns with measurements from the manual inclinometer, with a difference not exceeding 5 mm, confirming the reliability of this method. Concrete struts exhibit a transition of internal forces from compression to tension with staged excavation sequence. Differential settlement near the central column pile amounts to approximately 20 mm, highlighting the need for focused control. Soil heave at the excavation base shows a persistent increase down to 50 m depth, indicating that monitoring depth requires further extension. Lateral earth pressure outside the pit initially decreases and then rebounds with depth, exhibiting a significant coupling effect with retaining structure deformation. The FBG-based system effectively overcomes the temporal and spatial limitations of conventional monitoring techniques and offers a novel approach for automated foundation pit monitoring. Future research will aim to expand monitoring depth and integrate intelligent early warning algorithms to enhance risk management.