Connecting Shenzhen and Zhongshan, the Shenzhong Link is a world-class cluster of cross-harbour projects with interconnections between islands, tunnels and bridges. The 24-kilometre-long passageway is expected to open to traffic in 2024. Earlier, Ir Albert CHENG, Executive Director of the Construction Industry Council (CIC), led industry leaders on a trip to the West Artificial Island to learn more about the innovative construction technology involved. Introducing the project, GAN Xingqiu, Deputy General Manager of CCCC First Harbor Engineering Co., Ltd (CCCC-FHEC), said, "This project of the century will greatly shorten the commuting time between the east and west sides of the Pearl River Estuary and help promote the development of the Guangdong-Hong Kong-Macao Greater Bay Area city cluster.
Reducing Travel Time from Two Hours to a Half
The project team of Shenzhong Link first started the research stage in 2002. After thorough planning, they adopted the East Tunnel and West Bridge approach. The passageway, which runs from Shenzhen on the east bank of the Pearl River Estuary to Zhongshan on the west bank, comprises a 6.8-kilometre-long steel-shell concrete immersed tube tunnel, the West Artificial Island, the 1,666-metre-long Lingdingyang Bridge and the 580-metre-long Zhongshan Bridge. With the commissioning of this eye-catching project, the commuting time from Shenzhen to Zhongshan will be reduced from two hours to half an hour.
Innovative DSM Technology Helped Speed Up Island Formation
As the West Artificial Island plays a pivotal role in the transition between bridge and tunnel, its construction commenced as early as December 2016. It is a rhombus-shaped island, 625 metres long and 456 metres wide, with an area of 137,000 square metres, which looks like a 'kite on the sea'. The "kite" is made up of 57 steel cylinders with a diameter of 28 metres and a weight of about 600 tonnes each. Over the years, CCCC has led a number of key projects such as the Hong Kong-Zhuhai-Macau Bridge. However, when the team studied the foundation of the West Artificial Island for the Shenzhong Link, they discovered that the seabed of the Island was unevenly hard and soft. With rich experience and an innovative mindset, the project team swiftly turned crisis into opportunity. They invented the Deep Slurring Mixing (DSM) Technology, which means to soften the geology of the construction area by drilling and injecting mud into the sand layer with the help of an engineering ship. This has provided a solid foundation for the steel cylinder sinking process.
World Record For Largest Steel Cylinder Structure
After successfully resolving the unevenness of the seabed, the team used the 4,000-ton crane vessel "Yihang Jintai" with 12 hydraulic vibratory hammers to create a vibrating and sinking system with a maximum weight capacity of approximately 5,800 tons. Throughout the entire sinking process, the team was equipped with a visualisation, automated measurement and command system, which greatly enhanced efficiency and safety. From December 2016, when the construction of the West Artificial Island started as a pioneer project, to September 2017, when the last steel cylinder was sunk in place, the main structure of the West Island was formally completed within a short period of time. “The construction process of the West Artificial Island also broke the world records for the largest steel cylinder structure and the largest vibration hammer set," said Mr. YUE Yuanzheng, General Manager of CCCC's Shenzhong Link Project.
With the completion of the steel cylinder vibro-sinking works on the West Artificial Island, the team then started to implement water stop between the island tunnel and the island wall. Mr YUE said that the island tunnel was constructed on both sides by means of a retaining wall structure, while a water stopping steel plate was used between the retaining wall and the steel cylinder to form a secondary waterproofing system. The final part of the artificial island project is the precipitation and backfilling of the island, and the subsequent works include the treatment of soft ground, island water stop, island wall structure and protection, rescue pier, tunnel management station and other island facilities, which will play a key role in this mega project when it opens next year.
