Low-Disturbance Curtain Grouting for Large-Diameter Shield Underwater Docking: Multi-Scale Testing, Numerical Analysis, and Field Application

As underground space development advances toward long-distance and high-water-pressure scenarios, underwater shield docking has become a key technical challenge. To control grouting-induced disturbance during underwater shield docking, this study develops a low-disturbance curtain grouting design and control framework for a large-diameter shield operating under high water pressure. Taking the Jiangyin–Jingjiang Yangtze River Tunnel as the engineering background and focusing on its alternating silty fine sand and silty clay strata, a comprehensive methodology integrating in situ grouting tests, large-scale physical grouting tests, three-dimensional numerical simulations, and on-site monitoring was employed. The study systematically reveals the diffusion law of grout pressure and the superposition mechanism of additional stress during grouting. Key findings include: (1) In sandy strata, the grouting pressure exhibits a significant influence range of 0–3 m, with a peak additional pressure of 1.0 MPa, showing an inverse relationship with diffusion distance. In clay strata, the peak pressure reaches 1.4 MPa with a dissipation cycle of approximately 6 days. (2) Continuous grouting produces a pronounced pressure superposition effect, which is substantially stronger in silty clay than in sandy strata; a skip-hole interval of ≥3 holes effectively mitigates pressure accumulation. (3) Stress concentration near the shield body is prominent, with the maximum additional stress reaching 1.0 MPa. Numerical simulations indicate a maximum shield displacement of 19.3 mm and a localized von Mises stress of 355 MPa, slightly exceeding the nominal yield strength of 345 MPa and indicating the onset of local yielding. This localized yielding identifies a critical stress control region of the shield body and highlights the necessity of limiting grouting-induced stress accumulation. Based on these insights, a graded grouting parameter control strategy is proposed to ensure deformation compliance with engineering requirements. Field monitoring during the grouting stage showed that the optimized strategy effectively limited grouting-induced pressure accumulation and structural response. After recalibration using the actual construction loading and structural boundary conditions, the numerical prediction at the critical shield waist monitoring location showed good agreement with the corresponding field measurement. These results support the feasibility of the proposed low-disturbance grouting framework under the investigated project conditions. This field application validates the feasibility and effectiveness of the proposed method under the geological and hydraulic conditions of the Jiangyin–Jingjiang Yangtze River Tunnel and provides a methodological reference for low-disturbance curtain grouting design in shield docking projects with comparable conditions. Further validation across different geological and hydraulic environments is required before the proposed parameters can be generalized.