Recently, the Shizimen Tunnel Project, known as "the first ultra-deep foundation pit near the coastline of South China" , was opened to traffic by the Foundation Company of the First China Construction Third Engineering Bureau Company.
The project is located in the South Bend urban area of Zhuhai City and the Hengqin Guangdong-Macao Deep Cooperation Zone. The tunnel is a single-hole two-way four-lane tunnel with a total length of 1905 meters for the left line and 2657 meters for the right line. It is one of the shield tunnels with the largest diameter in the marine environment in China. After opening to traffic, it will become an important transportation hub linking Hengqin and the main urban area of Zhuhai, weaving an all-weather safe channel for Zhuhai Hengqin to communicate with the outside world, which is of great significance to the improvement of the road traffic network in Dawan District.
The lean construction
project is located around the Cross Gate Business Center , where there are many projects under construction and large-scale activities. Therefore, the project department with heavy tasks of relocation and coordination in the early stage relies on the ingenuity of "graded docking" and the tenacity of "communication and co-prosperity" . Within half a year, it facilitated the transfer of multiple sites to complete the relocation of a large number of pipelines, such as power, communications, rainwater and sewage, and cleared the way for the follow-up construction. The minimum clear distance between the left side of the
South Bend Avenue and the municipal underpass tunnel under construction is only 0.35 meters, and the minimum clear distance between the left side and the Zhuji Intercity Railway under construction is 8.45 meters. After consulting a large number of engineering data and repeated comparison and selection of several construction schemes, the "two piles and one solid construction method" - "common pile reinforcement", "short pile lock foot" and "surface reinforcement" were finally determined , which ensured the construction quality and protected the adjacent existing buildings.
The project includes the construction of the open-cut tunnel and the working shaft of the north-south bank connecting line. Among them, the starting well on the south bank is the key control project, and the construction difficulty of the reinforcement cage of the diaphragm wall refreshes the record in Zhuhai area. The construction of all 40 diaphragm walls was successfully completed more than 20 days ahead of schedule . At the same time, the "wheel inspection method" was used to cover the quality and safety of the working wells in all work areas to ensure the performance of the contract, and the construction of the diaphragm wall of the working wells on the north bank was completed 57 days ahead of schedule, which was fully recognized by the owners and all parties involved in the construction.
As the first ultra-deep foundation pit project along the coastal shoreline in South China, the construction of Shizimen Tunnel Project is faced with poor geological conditions, difficult construction involving iron, strong corrosiveness of coastal groundwater and many underground obstacles. There are five difficulties in earthwork excavation near urban rail transit and existing buildings. The scientific research team of the project has devoted themselves to studying and referring to various materials to overcome the difficult problems one by one.
The project adopts the mature experimental simulation method at home and abroad, innovatively develops the concrete pouring technology of the side wall of the foundation pit under the condition of permanent and temporary combination, and the construction method of the waterproof node of the steel pipe column and the bottom plate. To realize the efficient construction of the side wall of the main structure and the re-improvement of the anti-seepage performance of the structure, the project creates a common technology for the transformation of the existing retaining piles under the condition of the close proximity of the new and old foundation pits, and provides a new technical scheme for the enclosure of the foundation pits under the condition of the close proximity (parallel) of the ultra-small clear distance foundation pits. Then a complete set of construction technology for the reconstruction of the existing retaining piles is formed , which provides a complete set of construction scheme for the construction of the retaining piles shared by the new and old foundation pits.
The project applies the construction technology of new tunnel crossing the existing urban rail in soft soil area, reduces the disturbance of reinforcement construction to the underlying urban rail, meets the deformation control standard of soil unloading to the underlying urban rail tunnel, and reaches the international advanced level. During the construction process, the project has obtained 21 patents, 9 papers and 4 construction methods, and won the Science and Technology Progress Award of China Construction Enterprise Association and Guangdong Municipal Association, as well as a number of BIM and QC awards. Among them , "Ultra-deep Silt Foundation Pit Horizontal Support Construction Device and Construction Method" has become the first American patent for municipal engineering obtained by the Bureau.
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