Shenzhen–Zhongshan Subsea Tunnel Project

Technical Challenges 

1. Extreme difficulty in floating and installation control of ultra-large immersed tubes: Each immersed tube segment is about 165 m long and weighs about 80,000 tons, to be accurately placed on a soft seabed about 30 m deep. During float-out and sinking, buoyancy, gravity, waves, tides and the tube’s own attitude and displacement must be controlled simultaneously—posing stringent requirements on the hydraulic system’s output force, response speed and synchronization precision.

2. Under-water final joint installation & hydraulic jacking control precision: The tunnel’s final joint must be hydraulically jacked out underwater under high hydrostatic pressure and aligned with adjacent segments to millimetre-level accuracy. The installation must be completed within a limited tide window—hence the hydraulic system must perform pressure build-up, locking, jacking, retraction etc in a very short time, demanding extremely high reliability and stability.

3. Complex temporary anchoring, locking and attitude control system for the immersed tubes: During the sinking and connection process, each tube segment is held in position and attitude via temporary anchoring and locking devices, which rely on hydraulic actuators to apply and release prestress to maintain structural force balance. In the underwater environment, the system must provide sufficient and adjustable force yet avoid local damage to the steel-shell concrete structure under high static water pressure and flow impact.

4. High demands for electro-hydraulic integrated construction equipment and intelligent control: The project uses a large number of electro-hydraulic controlled smart bogies, hydraulic jacking support systems and intelligent casting systems, which must achieve multi-point synchronous jacking, automatic travel and real-time monitoring. These systems are distributed over long distances and multiple stations, requiring multiple hydraulic circuits to work in coordination and the integration with digital control platforms—raising the difficulty of system integration and commissioning.

5. Stringent requirements on hydraulic loading equipment for structural testing: To validate the performance of the steel-shell concrete immersed tubes’ joints and final connection, laboratories use large-tonnage hydraulic servo actuators and hydraulic jacks to apply complex combined loads (axial pressure + lateral cyclic loads). The testing must simulate marine environment and long-term vehicle loading, requiring the hydraulic system to offer high-precision displacement control and stable cyclic loading capability. The test results in turn inform the design parameters for the on-site hydraulic systems.