Leveling Construction of Gravel Foundation Bed of Dalian Bay Cross-Harbour Tunnel Successfully Completed
2022-08-03 18:19

On August 1st, after 10 consecutive days and nights of operation, the leveling construction of gravel foundation bed at E18 pipe joint of Dalian Bay Cross-Harbour Tunnel was successfully completed, which also marked the end of all leveling construction tasks of Dalian Bay Cross-Harbour Tunnel Project.


The main line of Dalian Bay Cross-Harbour Tunnel is 5098 meters long, of which the immersed tube cross-harbour tunnel is 3035 meters long, which consists of 13 straight pipe joints and 5 curved pipe joints. As the key process of immersed tunnel construction, gravel foundation leveling construction has extremely high technical content and quality standard, which is one of the prerequisites for immersed tube installation to achieve millimeter-level butt joint and ensure watertight.


The foundation of Dalian Bay Cross-Harbour Tunnel is large in scale, in which the gravel foundation is 37 meters wide in straight section and 40 meters wide in curve section. The total area of all pipe joint foundation beds is 115,000 square meters, and about 210,000 cubic meters of gravel is needed. Different from the seabed situation of Hong Kong-Zhuhai-Macao Cross-Harbour Tunnel, the geological conditions in Dalian Bay are special, and most of them are rock foundations. There will be a lot of cracks and complexity in the foundation trench slope after reef blasting, and there is a risk of instability in the slope due to large load pile insertion, so there is a great risk of full lifting pile insertion.


After three years' research and more than 100 special technical discussions, the project team finally decided to adopt the full floating bed leveling process. Full floating gravel bed leveling construction technology is proposed for the first time in China, especially for the complex geological conditions of Dalian Bay seabed. In April 2020, the project team carried out a one-month full floating leveling test, and the test results showed that the qualified rate of full floating bed leveling could reach over 95%, which could fully meet the construction requirements. By adopting this technology, not only the quality standard of 40 mm can be met, but also the excavation amount of foundation trench can be saved, the leveling time can be shortened, the service life of pile legs of leveling ship can be effectively prolonged, and the safety of leveling ship construction operation can be improved.


The ship "Jinping 1" used in gravel bed leveling construction is the first platform-type high-precision deep-water riprap leveling ship in China, which is a special construction ship designed and built for gravel cushion laying of immersed tunnel. As a meritorious ship in the construction of immersed tunnel of Hong Kong-Zhuhai-Macao Bridge, "Jinping 1" realizes the automatic and integrated management of laying construction operations such as leveling ship positioning, gravel transportation, scraper adjustment, trolley movement control, material level control and synchronous detection. The platform ship has high construction efficiency, high leveling accuracy and strong operation adaptability, and its whole ship function, construction technology and leveling accuracy have reached the world advanced level.


After the leveling construction is completed, the project team will make every effort to promote the installation of E18 pipe joint and final joint. It is expected that the docking between final joint and E18 pipe joint will be completed by the end of this month, when the submarine section of Dalian Bay Cross-Harbour Tunnel will be fully connected.