Media Focus | The first of all! The shield tunnel section between Meishan North Station and Music Square Station of the Chengdu-Meishan S5 suburban Railway was successfully connected

On January 9th, with the cutter head of the No. 6 shield machine breaking through the hole, the left line of the shield tunnel section between Meishan North Station and Music Square Station of the Chengdu-Meishan S5 Line of the urban (suburban) railway, which was constructed by the Jiaojian Group, was successfully connected four months ahead of schedule. It is the first shield tunnel section to achieve a breakthrough along the entire line, marking a breakthrough in the construction of the Chengdu-Meishan S5 Line project.

The Chengdu-Meishan Line of the intercity (suburban) railway is approximately 59 kilometers long, starting from Honglian Station in Tianfu New Area, Chengdu and ending at Meishan East Station of the Chengdu-Guiyang High-Speed Railway. It has 13 stations in total. The vehicles used are 4-car formations of the intercity A-type, with A maximum operating speed of 160 kilometers per hour. The total length of the shield tunnel sections in both directions along the entire line is about 19 kilometers. It is a key project in the construction of the Chengdu-Meishan Line of the intercity (suburban) Railway.

The tunnel that was completed this time is approximately 2.4 kilometers long. The project lasted for 298 days and was constructed using a domestic 8.2-meter large-diameter shield machine. During the tunneling process, information management means were fully utilized. Through the intelligent tunneling control technology of shield tunnels, the various working parameters of the shield machine during the tunneling period were monitored, analyzed and dynamically adjusted in real time and intelligently, fully ensuring the quality of tunnel construction and providing a strong guarantee for the smooth breakthrough of the first shield section of the Chengdu-Meishan Line.

As of now, the main structures of all three underground stations along the Chengdu-Meizhou Line have been capped, the platform layer structures of four elevated stations have been completed and are ready for bridge erection machines to pass through, the main structures of two open-cut stations have been capped, and all nine shield machines have been launched, with a total excavation of over 7,000 meters.

The successful breakthrough of the first shield tunnel section of the Chengdu-Meishan S5 suburban Railway has provided valuable technical experience for subsequent shield construction and laid a solid foundation for the early completion and operation of the entire project.

Extended Reading

The Chengdu-Meishan (S5) Suburban Railway project is a key project in the "Multi-Level Rail Transit Plan for the Chengdu-Chongqing Twin-City Economic Circle" issued by the state. It is an important transportation infrastructure connecting the Chengdu suburban railway network and the main channel for the integration of Chengdu and Meishan. After its completion, it will effectively shorten the time and space distance between Chengdu and Meishan. Promoting the efficient aggregation of industries, population and various production factors between Chengdu and Meishan, and strengthening Chengdu's leading role as a central city, is of great significance for enhancing the core level of Chengdu, promoting the construction of the Chengdu-Chongqing Twin-City Economic Circle and the integrated development of Chengdu, Deyang, Meishan and Ziyang.

The left line of the shield tunnel section between Meishan North Railway Station and Music Square Station, which was successfully connected this time, is 2,413.1 meters long. The designed minimum burial depth is only 5.7 meters, and the minimum radius of the planar curve is 500 meters. It passes through a large number of farmfields, irrigation canals, old sheds and main urban roads. It also passes through a 4-meter by 4-meter super-large municipal drainage network on the side, which is 1,581 meters long. The tunnel body passes through micro-gas strata, low-gas strata and water-rich sandstone, pebble and mudstone composite strata, while the arch top passes through strongly weathered mudstone strata. The construction is highly risky and difficult.

To ensure the smooth progress of the project construction, the project team has adopted multiple measures and implemented precise policies. First, optimize the construction design. Invite industry experts for argumentation many times, appropriately adjust the tunnel burial depth and optimize the excavation slope. While avoiding adverse geological conditions, effectively reduce the risk of surface settlement. Second, improve the construction equipment, introduce advanced experience and technology in combination with the actual situation of the construction site, enhance the configuration of shield machines and the control ability of tunneling and excavation, effectively reduce the wear of equipment caused by long-distance tunneling and pebble strata, and solve problems such as mud gushing during the construction process. Thirdly, advanced technologies are applied, such as "single pipe single pump", medium shield mud injection, double-liquid synchronous grouting, and the interlocking of wind power in the gas tunnel, effectively addressing the instability of the excavation face in composite strata, the difficulty in settlement control, the floating of segments, and the shield construction of gas tunnels. Fourth, we will practice the concept of green development. In combination with the research project "Multiphase Classification Treatment and Resource Recycling and Utilization of Shield Construction Waste and Carbon Reduction Assessment", we will implement multi-stage screening, multiphase separation of slurry and water, and slurry dewatering of shield construction waste. The construction water will be recycled, and the screened sand and mud cakes will be solidified and reused as construction materials, achieving harmless treatment of shield construction waste and "zero" discharge of wastewater and waste.