Assessment and Control of Construction Risk for a Super-Sized Quasi-Rectangular Pipe-Jacking Tunnel Adjacently to High-Speed Railways: A Case Study

Constructing super-sized quasi-rectangular pipe-jacking tunnels beneath high-speed railways presents a significant risk to both the railways and the tunnels. This paper uses expert inquiry, numerical simulation, fuzzy comprehensive evaluation, and on-site monitoring to assess and control risks for constructing a super-sized quasi-rectangular pipe-jacking tunnel project beneath high-speed railways. An assessment system including 18 factors from 6 aspects is built by integrating existing literature, expert consultation, and causality analysis. As the insufficient number of projects, the Analytic Hierarchy Process (AHP), Fuzzy Comprehensive Evaluation Method (FCEM), Delphi method, and numerical simulation are employed to establish a risk assessment model. The pre-support roof construction (P-SRC) technology is proposed to control tunnel construction risks. The actual scenario on site examines the validity and practicality of the evaluation model and control measures. The results indicate that the super-sized quasi-rectangular pipe-jacking tunnel sections for planned and operational high-speed railways belong to the level I risk, requiring risk reduction measures. The artificial borehole piles + D-shaped beams scheme and pile-plate structure scheme decrease the construction risk from level I to IV, and the evaluated risk results and control effect are in good agreement with actual construction conditions. The proposed risk assessment method and control technology are reasonable and reliable, providing a scientific reference for similar projects.