On July 15, the right line of the TBM section between Qixinggang Station and Chongqing Station of the north extension project of Chongqing Rail Transit Line 18 was successfully holed through, marking phased progress in the project construction.

The tunnel in the section between Qixinggang and Chongqing Station is 1,480.743 meters long, of which the shield-driven section is 1,341.402 meters, with a minimum turning radius of 500 meters and a maximum gradient of 34.48‰. The buried depth of the section is about 28 meters to 92.7 meters. The 6.86-meter composite earth pressure balance shield machine "Yuxing No. 1", independently developed by CCCC, was used for the tunneling construction.

It is understood that the Qixinggang-Chongqing Station section is located in the central urban area of Chongqing, where the construction environment is sensitive and complex, and the construction risks are high and the difficulty is great. During construction, "Yuxing No. 1" had to pass alongside the pile foundations of the Meiyu Junyue Hotel and underneath key structures such as the Zengjiayan Tunnel and Rail Transit Line 3. The control of its tunneling attitude, the quality control of segment erection during small-radius tunneling, the scientific disposal of shield muck, and the coordination of various processes and safety control while crossing complex strata were key difficulties in the construction.

In view of the special environment of the project construction, the contractor made efforts in safety risk control, green and civilized construction, and smart site creation, and adopted a series of measures to ensure the safe holing-through of the tunnel.

To ensure that the TBM tunneling smoothly crosses major risk sources, the project conducted on-site surveys of the risk sources in advance, formulated special construction plans and emergency response plans, and organized experts for plan review and technical guidance on multiple occasions, providing solid technical support for construction through the risk sources. At the same time, a digital system was used to monitor the tunneling process in real time, promptly record shield tunneling data, parameters, and geological conditions, and continuously optimize tunneling parameters, ensuring smooth TBM tunneling and minimizing the impact on the surrounding environment.

To solve the difficulty of shield muck disposal in limited space, the project, in response to the narrow site conditions, developed a shield construction site layout plan and a construction organization and management system suited to the actual production of the project. By reasonably dividing areas, the site was basically made to meet the requirements. A large shield muck environmental protection treatment system was also introduced, enabling the maximum daily muck treatment capacity at the Qixinggang-Chongqing Station section site to reach 1,000 cubic meters. The sand and gravel, mud cake, clean water, and other materials separated from the shield muck can all be reused, successfully achieving reduced-volume transportation, environmentally friendly treatment, and resource utilization of shield muck.

In addition, the project dynamically reviewed and analyzed the internal deformation of the tunnel structure at the construction site, adopted the method of a dual-liquid grout water-sealing ring and secondary supplementary grouting to quickly stabilize the segments and prevent the assembled segments from dislocating or deforming. Based on the real-time data of the shield machine's fully automatic guidance system, it controlled the shield tunneling parameters, increased the frequency of segment attitude measurement, and promptly adjusted and corrected the shield machine's attitude, laying a solid foundation for building a high-quality project.