“Qiantang Jixiang” 15-meter mega Slurry TBMProject: Hangzhou Genshan East Road Crossing River Tunnel
Location: Hangzhou City, Zhejiang Province, China
Customer: China Railway 14th Bureau
Innovation of mega Slurry TBM
On June 28, the ‘Qiantang Jixiang’ 15-meter mega Slurry TBM rolled off the assembly line at CRCHI. The excavation diameter of the equipment is 15.01 m, its total length is about 130 m, total weight is about 4300 t, installed power is about 9755 kW, rated torque is 42784 Nm, and the maximum excavation speed is 50 mm/min. It will be used for the construction of crossing river tunnel of Genshan East Road in Hangzhou, China.
Project Overview
The Genshan East Road Crossing Tunnel Project in Hangzhou is designed as an urban expressway, including a cross-river tunnel, a comprehensive pipeline gallery, a ground connection line project and supporting auxiliary projects. The total length of the project is 4,725 m (including ground connection roads), and the total length of the tunnel is 4575m. About 3160 m of the tunnel will be using a TBM. The length across the Qiantang River is about 2.3 km. It has a double-tube circular structure and six lanes in two-way. The design speed in this tunnel is 80 kilometers per hour.
Engineering Challenges
The tunnel section advancing with TBM passes mainly through soft soil layers, such as silty soil, mucky soil, and cohesive soil, with a maximum buried depth of up to 44.2 m. The main difficulties in the construction process are as follows:
- The tunnel excavation section has a diameter of 15.01 m, and the stability of the tunnel face is difficult to control. The TBM should have the ability to accurately control the stability of the tunnel face to prevent it from collapsing.
- For advancing in soft soil, poor stratum bearing capacity and poor permeability will cause the TBM to sink, and the segments to float up. Therefore, it demands high precision and control of the TBM and high quality of segment box culvert assembly. In addition, due to the high content of viscous particles in the formation, a large capacity of the ground slurry treatment system is required. Since the problem of mud cakes often occurs for the cutterhead, the TBM should have the ability to prevent mud cakes and efficiently process them.
- Long-distance crossing of the Qiantang River, and construction at the bottom of the river has high requirements on the reliability of the TBM and the balance of the excavation face, avoiding the breakthrough of the river bottom.
- The length of the section is 3.2 km, which requires high reliability for TBM seals, including main drive seal and tailskin seal, and high requirement for wear resistance of the cutterhead, cutters, and slurry pipelines.
- Since there may be harmful gases in the formation, the TBM should have reliable harmful gas detection devices and be equipped with a high-power ventilation system to discharge the gases on time.
The CRCHI R&D department has tackled all the key problems with the Qiantang Jixiang 15-meter mega Slurry TBM. The machine was designed to have soft soil cutterhead which features cutter change in free air, frequency conversion motor for the main drive and a retractable cutterhead. Cutting-edge technological advancements include main drive seal which is automatically pressurized, high precision gas-liquid pressure balance control, simultaneous lifting and assembly of segments and box culvert. Therefore, the performance reliability and geological adaptability of the shield machine have been improved dramatically. The development of this TBM has strongly promoted the development process of China’s mega Slurry TBM.
