Objective Sectional excavation in underground engineering will induce disturbances in surrounding rock mass, altering its mechanical parameters and complicating construction parameter selection, thus compromising structural stability and safety. To dynamically obtain more accurate rock mass mechanical parameters to guide construction parameter selection and ensure structural stability and safety, it is essential to perform dynamic back-analysis of mechanical parameters during the sectional excavation process.

Method Relying on the Ciqikou Station project of Chongqing Rail Transit Line 27—a mined double island four-track passing subway station—the cohesion, elastic modulus, and stress release rate of each stratum are selected as back-analysis parameters. Based on a self-developed finite element model, a displacement back-analysis method optimized by orthogonal experimental design is used to dynamically back-analyze the mechanical parameters of surrounding rock during Ciqikou Station main tunnel excavation, which are used to analyze surrounding rock stability throughout the excavation process.

Result & Conclusion The displacement back-analysis method optimized by orthogonal experimental design can effectively obtain the inverted mechanical parameters of surrounding rock across various excavation stages. Such calculated displacement values during each sectional excavation process match well with the measured values. Compared with the traditional calculation results using empirical parameters of the surrounding rock, the dynamic back-analysis results can describe the variation of surrounding rock parameters during sectional excavation more realistically and accurately, providing a basis for the dynamic optimization of construction parameters during the excavation process.