Vision-Based Deformation Monitoring and Risk Analysis of Adjacent High-Speed Railway Piers Under Full Construction Process of New Bridges

The proliferation of high-speed railway (HSR) networks necessitates frequent construction activities adjacent to operational lines, posing significant risks to the structural integrity and safety of existing infrastructure. This study addresses the critical need for a comprehensive framework to assess and monitor the deformation of HSR piers throughout the entire construction process of a new, nearby bridge, which includes the cumulative effects of both substructure and superstructure construction. A hybrid methodology integrating quantitative risk assessment and real-time, non-contact monitoring was developed and implemented. A risk evaluation model was established using the Analytic Hierarchy Process (AHP) to structure the problem, combined with Triangular Fuzzy Numbers to handle the inherent uncertainties in expert judgments. The Fuzzy Comprehensive Evaluation method was then employed to quantify the risk levels of various construction stages. Concurrently, a vision-based monitoring system utilizing Digital Image Correlation (DIC) technology was deployed to capture the three-dimensional deformation of adjacent HSR piers with high precision and frequency. The case study, focusing on the construction of a new bridge crossing the operational Beijing-Shanghai HSR, demonstrated the application of this framework. The risk assessment model identified the pile cap and pier construction phase as the highest-risk stage, with a risk weight of 0.311. The DIC monitoring system, validated against total station measurements with a relative error of less than 5%, recorded the cumulative pier deformations throughout 31 distinct construction stages. The maximum recorded deformations in the transverse, longitudinal, and vertical directions were all maintained within the early warning threshold of ±1.2 mm stipulated by railway regulations. The study confirms that the integrated AHP-Fuzzy and DIC framework provides a robust paradigm for proactive risk management in adjacent-line construction projects. The risk model accurately predicted the most critical construction phase, and the DIC system offered a reliable and efficient solution for real-time safety assurance. The findings validate that with appropriate risk-informed monitoring, the impact of new bridge construction on existing HSR infrastructure can be effectively controlled within safe limits, offering a valuable reference for similar engineering projects globally.