Shenzhong Link – Immersed Tunnel Uncovers Potential of Prefabrication

The digitalisation of China's construction industry is advancing by leaps and bounds. The project team's innovative thinking combined with prefabrication techniques attributes the success of Shenzhen-Zhongshan Link, the world's largest steel-shell concrete immersed tunnel. Ir Albert CHENG, Executive Director of the Construction Industry Council (CIC), visited the tunnel and learnt how the electric smart trolleys, automatic intelligent pouring system and smart site safety system have contributed to the safety and efficiency of this "Project of the Century".

Electric Hydraulic Trolley and Intelligent Pouring System

The 24-kilometre-long Shenzhong Link is a world-class cluster of cross-harbour projects with interconnections between islands, tunnels and bridges. It is expected to be commissioned in 2024, which will reduce the travelling time from Shenzhen to Zhongshan from the original two hours to half an hour. The subsea tunnel, which runs from Shenzhen to the Western Artificial Island, has a total length of 6,845 metres. The immersed tube section, which consists of 32 immersed tube sections and one final joint, has a length of 5,035 metres, and is the world's first two-way eight-lane, steel-shelled concrete immersed subsea tunnel.

CCCC Fourth Harbour Engineering Co., Ltd. (CCCC4) has years of experience in the construction of immersed tunnels, and has previously been involved in the construction of the Hong Kong-Zhuhai-Macao Bridge project. This time, the project team is welcoming an even larger immersed tunnel project. While introducing the Shenzhong Link, Mr. CHEN Wei-bin, General Manager of the Technical Centre, said, "In every immersed tunnel project, we are improving the effectiveness of prefabrication. When it comes to the Shenzhong Link, the production capacity increases to 40 days for one tube section." He added that this was made possible by the creation of intelligent trolley technology after continuous practice and research.

Each intelligent trolley has a loading capacity of 800 tonnes. When the precast steel- shell arrives at the unloading area of the prefabrication factory, 200 sets of trolleys will run simultaneously to deliver it to the intelligent pouring area. By using big data, the system can automatically pour concrete within seconds and control the speed of concrete placement, which is more efficient than traditional pouring machines and can greatly reduce concrete wastage. Each steel-shell concrete immersed tube weighs up to 80,000 tonnes. After prefabrication, the steel-shell concrete immersed tubes will be transported by intelligent trolleys with a carrying capacity of 160,000 tonnes to the shallow dock area of the factory, ready for shipping and installation. The whole process of immersed tube prefabrication is carried out in the factory. Mr CHEN Wei-bin said that efficiency and quality are greatly enhanced, and the working environment is safe and comfortable without the need to be exposed under sun and rain.

"Yihang Jinping 2" Delivers Top Levelling Technology

The Shenzhong Link is a major national project and many different teams have been working on it for years. CCCC4 has been contributing prefabrication technology and different innovative technologies. CCCC First Harbor Engineering Co., Ltd (CCCC-FHEC) has also assisted the project in many ways, including the use of its self-developed "Yihang Jinping 2" to help in the seabed foundation work of the subsea tunnel. "The Yihang Jinping 2" is a self-elevating gravel laying and levelling vessel with a length of 98.7 metres and a width of 66.3 metres, which is close to the size of an international standard football pitch. It is capable of performing tasks such as positioning, pile lifting, gravel conveying and levelling, and quality checking, achieving integrated management throughout the construction process. It is also highly resistant to wind and waves, allowing high levelling speed and accuracy. With the help of "Yihang Jinping 2", levelling work for one standard tube section can be completed in 3 to 4 days.

Smart Site Safety System in Action

During his visit, Ir Albert CHENG commended the innovation of the Shenzhong Link, in particular the Smart Site Safety System. For instance, CCCC4 built a smart monitoring hall for the prefabrication factory, which provides an overview of construction processes on screens to effectively manage and ensure safety. CCCC-FHEC also uses smart helmets with BeiDou Navigation Satellite System and front camera to monitor the team's position, safety and health in real time during construction.

The main structure of the Western Artificial Island and the Lingdingyang Bridge were also completed in September 2017 and April 2023 respectively. In June 2023, the final joint of the subsea tunnel successfully connected to the last tube segment, bringing this mega project to the final stage. When it opens to traffic next year, it will definitely bring the Greater Bay Area closer together, promote development, and benefit the public in various aspects.