Abstract: In this study, a case study is conducted on the Jiangyin-Jingjiang Yangtze River Tunnel Project and numerical analyses, model tests, and field verifications are employed to systematically analyze the key technical issues associated with breakthrough construction of a large-diameter shield docking section in high-water-pressure and permeable strata, thus ensuring the stability of strata and structures. A deformation control method involving “layered dismantling and unloading with synchronous construction and loading” is proposed for dismantling the existing structures and constructing the new structures within the docking section, resulting in a maximum structural displacement of 7.7 mm. The influence of local and overall failure of freezing pipes on the temperature of frozen strata is analyzed, clarifying the stability characteristics of the frozen body under the extreme working condition of 48-h freezing suspension. Comparative tests of three steel plate cutting methods—manual cutting, semiautomatic cutting, and water jet cutting—are conducted, determining the manual cutting featuring high efficiency and good operational flexibility as the main method for onsite structural dismantling. Steel plate welding tests are performed under a low-temperature environment of －30 ℃, and the welding quality is verified to satisfy the design requirements through mechanical performance tests. In addition, a thermal disturbance evaluation system is established to effectively verify the construction safety of the frozen wall. Process tests on the filling technology of steel shell concrete are carried out to verify the practical method for ensuring the filling compactness of concrete. A three-step dismantling method for the main shield drive in narrow space is proposed and verified through process tests. After onsite implementation of this method, the maximum settlements of the leading and following shield machines are 5.3 mm and 7.7 mm, respectively, realizing the continuous and efficient dismantling of two 300 t main drives.

Key words: super-large diameter shield, riverbed docking, breakthrough construction, wall-adhering thermal disturbance, self-compacting concrete, main drive dismantling, Yangtze River Tunnel