On May 19, Guangdong Transportation Group announced that at 11:58 a.m., after nine and a half months of work, concrete pouring for the open-cut section of the cast-in-situ tunnel on the west artificial island of the Shenzhen-Zhongshan Link was completed, marking the completion of the main cast-in-situ tunnel structure on the island and laying an important foundation for the transition between tunnel, island and bridge.

"The main cast-in-situ tunnel on the west artificial island of the Shenzhen-Zhongshan Link is a key hub project connecting the immersed tube tunnel with the offshore bridge and realizing the bridge-tunnel transition. It is divided into a buried section and an open-cut section, both using open-cut cast-in-situ reinforced concrete structures. The buried section was completed in August last year, and next we will continue with construction of the ramp tunnels on both sides of the main line," said Liu Xiaofeng of the Island and Tunnel Engineering Management Department of the Shenzhen-Zhongshan Link Management Center.

It is understood that the main cast-in-situ tunnel on the west artificial island of the Shenzhen-Zhongshan Link is 475 meters long in total, of which the buried section is 175 meters long and connects with the first immersed tube element E1; the open-cut section is 300 meters long, connected to the buried section on the east and to the roadbed section on the west, forming an island-bridge transition, and connected with ramps on both sides to form an interchange on the island.

"The cast-in-situ tunnel on the west artificial island of the Shenzhen-Zhongshan Link is a super-large open-sea open-cut cast-in-situ tunnel with eight lanes in both directions. The open-cut section is divided into 10 segments for pouring, with a maximum single concrete pour of 2,000 cubic meters. At the same time, the cross-sectional dimensions gradually widen, reaching a maximum of 84.33 meters, making crack control in mass concrete difficult," said Wang Gang, director of the Production Management Department of the Shenzhen-Zhongshan Link Project Department of CCCC First Harbor Engineering Co., Ltd. "According to the design requirements, an arc-shaped roof slab and arc-shaped beams are installed where the open-cut section meets the buried section. Seen from a distance, the trough section of the open-cut tunnel is U-shaped and the light-reducing section is mountain-shaped. The complex structural forms, numerous large and irregular formwork, the large volume of scaffolding, and the narrow working faces have all brought certain challenges to construction."

Starting from the goals of ensuring structural durability and controlling cracking in mass concrete, the construction team developed a mass concrete mix with low temperature rise, low shrinkage, high strength and high density, ensuring the crack resistance and impermeability of the cast-in-situ tunnel. At the same time, the team developed an intelligent temperature control system to monitor the temperature of mass concrete in real time during construction, automatically collect and analyze monitoring data, and dynamically adjust circulating water, achieving automated and intelligent control and solving the problem of crack control in mass concrete.

The Shenzhen-Zhongshan Link is a cross-sea cluster project integrating "bridge, island, tunnel and underwater interchange," with a total length of 24 kilometers. At present, more than 10,000 builders are advancing construction of the Shenzhen-Zhongshan Link. Nine immersed tube elements of the subsea tunnel have been installed, completing 1,443.5 meters, and the 10th element is planned to be immersed in June. The main tower of the Lingdingyang Bridge has reached an elevation of 240 meters, and the main tower of the Zhongshan Bridge has reached 160 meters. The two bridges and their two towers are expected to be topped out within this year. The project is planned to be completed and opened to traffic in 2024.