Construction Response Simulation Analysis and Construction Parameter Optimization of Curved Shield Construction under Rock-Soil Binary Stratum

Objective The rock-soil binary stratum is a typical upper-soft and lower-hard composite stratum. Due to its complex geological conditions, this stratum significantly influences the stratum deformation mechanism and mechanical response of shield tunnel construction in curved sections. It is crucial to carry out an in-depth analysis on the response under different construction conditions. Method Taking the shield tunneling construction between Tantou Station and Daoxiang Station section of Jinan Rail Transit Line 3 as the background, a research method combining numerical simulation and on-site monitoring is adopted to systematically analyze the key issues of surrounding rock deformation, segment stress and strain, and construction parameter optimization, revealing the construction mechanical responses of the two under the rock-soil binary stratum, and optimizing the construction measures and parameters on this basis. Result ＆ Conclusion The rock-soil binary stratum has a greater impact on curved tunnels than on straight tunnels, with the maximum curved shield tunnel displacement occurring at the left arch shoulder, and the affected range of the left arch shoulder in the curved section shield is larger than that of the vault. In the rock-soil binary zone, the surrounding rock deformation of the curved section shield is significantly greater than that of the straight shield, yet the deformation amplitude of the curved section shield tunnel remains smaller than that of the straight shield tunnel, with the vault settlement being more sensitive than the arch bottom uplift. The first and third principal stresses and deformations of the curved section shield segments are greater than those in the straight section, especially within 2 m from the rock-soil binary, the stress increase is significant. A comprehensive control scheme and corresponding parameters of "micro-disturbance refined excavation + inner tunnel advanced grouting reinforcement" are proposed, and its effectiveness is verified, revealing the influence law of the rock-soil binary stratum dip angle on the grouting reinforcement range, and pointing out that when the dip angle is less than 65°, the reinforcement width needs to be appropriately increased.