China Railway 2024-07-07 08:45 Beijing
Let the giant "Honghu" fly against the sea surface - a sidenote of the innovative sand filling and island construction technology of the East Artificial Island of the Shenzhong Passage of China Railway Tunnel Bureau
On June 30, the opening of the Shenzhen-Zhongshan Corridor further promoted the integrated development process of the Pearl River Estuary, and the Guangdong-Hong Kong-Macao Greater Bay Area is gradually moving from a blueprint to a prosperous one.
In the construction of the most difficult cross-sea cluster project in the world, the east artificial island undertaken by China Railway Tunnel Bureau can be described as the gateway project of Shenzhen, located on the south side of Shenzhen Bao'an Airport, close to the Fuyong Airport wharf, east of the Shenzhen section of the Guangzhou-Shenzhen Yanjiang Expressway under construction, and west of the project submarine tunnel.
As the first expressway underwater interchange in China, the east artificial island adopts the layout of "one body and two wings", connecting the side connection project of the Shenzhen section of the Guangzhou-Shenzhen Yanjiang Expressway under construction in the east and the submarine immersed tunnel in the west, giving full play to the hub function of the interconnection between the underwater tunnel and the road road.
The east artificial island is 930 meters long from east to west and 1,136 meters long from north to south, with a sea area of 476,300 square meters and a land area of 343,800 square meters, which is equivalent to 48 international standard football fields. Among them, the tunnel works include a 480-meter-long weir section tunnel, an 855-meter-long main line tunnel on the island, and four ramp tunnels for traffic transfer.
The East Artificial Island Project is located in the sea and land alternate sedimentary strata, with complex geological and hydrological conditions, and is affected by the aviation height limit of Bao'an Airport, the existing operation of the Guangzhou-Shenzhen Yangtze River Expressway and the Fuyong Wharf Channel, which has high safety risks for cross operations and underwater operations, and has extremely strict technical and construction requirements.
Difficulty 1: Guangzhou-Shenzhen Yanjiang Expressway is one of the core channels of the eastern urban agglomeration of the Pearl River Delta, the traffic pressure is large, the east artificial island and the weir section of the tunnel are under the existing Guangzhou-Shenzhen Yanjiang Expressway, and the island is reclaimed within the sea area of its 40-span pier cap, and the construction process can not affect the operation of existing projects such as Bao'an Airport and Guangzhou-Shenzhen Yanjiang Expressway, and the displacement and settlement of the high-speed piers along the Yangtze River shall not exceed 5 mm, and the control of the construction indicators of the island is extremely strict.
Difficulty 2: Located in the 8~15 meters deep silt layer, the displacement control of the bridge pier is extremely difficult, the total amount of sand filling exceeds 4 million cubic meters, and there may be a large area of arch siltation, tumbling and other phenomena during backfill construction, which leads to additional internal force and deformation settlement of the existing structure.
Difficulty 3: The geological improvement of the ultra-thick silt layer in the tidal affected area belongs to the white dolphin reserve and the water environment has high construction requirements.
In order to realize the purpose of building an island in the sea area of deep silt strata under the existing highway bridge and realizing the purpose of ensuring the safety of the bridge by filling construction, the construction team of China Railway Tunnel Bureau determined the direction and thickness of the island backfill by numerical analysis method, and innovatively proposed the key construction technology method of "first constructing the isolation steel plate (pipe) pile, then laying the sand quilt, and then layering symmetrical backfill".
Cofferdam protection. The pier abutment of the high-speed bridge along the river is protected by steel sheet piles and steel pipe piles, and the pier protection piles are constructed by static pressure pile planters and steel pipe piles constructed by resonance-free hammers. The innovative use of the steel pipe pile construction platform integrating wind prevention, operation and guidance can effectively reduce the impact of wind and waves, ship shaking and other verticality and improve the control accuracy. At the same time, the Leica TM50 automatic measurement robot is used for all-weather automatic observation, and the cumulative changes in the settlement and displacement of high-speed piers during the construction process are less than 1 mm, which realizes the safety protection of the existing bridges in the construction of islands in the sea area.
Quilting at sea. The construction team innovatively adopted the "sand quilt" method for sand filling operations, and made the sea sand into a bed of "sand quilt", which was evenly paved layer by layer around the bridge pier, effectively solving the problem of eccentric load. In order to ensure high-quality and high-efficiency construction, the construction team also set up a sea sand supply guarantee team, set up a special guarantee fund, and at the same time, according to the overall construction arrangement, inverted backfill nodes, coordinated various ship resources, and made every effort to ensure the supply of sea sand, and finally realized the daily output of blown sand from 5,000~10,000 cubic meters to more than 20,000 cubic meters, achieving stable and high yield.
Process combining. The innovative use of steel sheet pile + internal support + sand quilt + sand pump sand ship + sand separation device in a variety of ways to control the symmetrical backfill and single filling thickness, solve the rapid island construction prone to arch siltation and overwelling phenomenon, greatly improve the construction efficiency, and realize the deep silt layer reclamation island building bridge deformation index is strictly controlled within 5 mm of the construction problem.
As the first project in China to adopt the backfill sand construction technology under the bridge in deep silt strata, since the start of island construction in August 2020, the project team has overcome the construction difficulties such as bridge pier protection, control of underwater filling arch silt construction, great influence by tides, and layered symmetrical filling without reference of similar engineering experience, and it took less than 10 months to basically form the island body of the east artificial island, which fully proved the feasibility of the construction technology of island building in the sea area, and the settlement of the adjacent structures is controllable. The research results have strong reference significance for similar projects.
The artificial island in the east of the Shenzhong Passage during construction
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Executive Editor-in-Chief丨Li Yuan, Shen Su
Editor-in-charge丨Xu Huimin
Content source丨China Railway Tunnel Bureau
China Railway Rong Media Center