brief introduction
According to Bin Chen, Chairman of Shanghai Tunnel Co., Ltd., the north bank of Qianjiang Passage and Wiring Project is adjacent to Yan Guan Town, a tidal scenic spot. In order to protect the natural wonder of Qianjiang tidal bore, after repeated argumentation, the project finally decided to adopt the Qianjiang tunnel crossing scheme. This tunnel can be called the sister tunnel of Shanghai Yangtze River Tunnel. It is also constructed by shield method, with an outer diameter of 15.43m, double pipes and six lanes. It is one of the largest shield tunnels in the world. Chun Qing Road Tunnel, another river-crossing tunnel in Qiantang River, has a total length of 3,765 meters, of which the single-line length of the shield section is 1.767 meters, and the slurry balance shield with a diameter of 1.65 meters is adopted.
Qianjiang Tunnel is located in soft soil area, and the maximum buried depth in the middle of the river is about 38 meters. The tunnel has large span, long mileage, great technical difficulty, complex geological conditions and great construction difficulty. Shanghai Tunnel Engineering Co., Ltd., which undertakes the investment and construction of Qianjiang Tunnel, has just successfully completed the two-way 15km promotion task of Shanghai Yangtze River Tunnel.
Xing Luqing, Investment Promotion Bureau of Shaoxing City, said that Qianjiang Tunnel is another key project after Ningbo Hangzhou Bay Bridge and Hangzhou Bay Jiashaohe Bridge. On the one hand, these tunnels promote the construction of the industrial belt around Hangzhou Bay in Zhejiang, on the other hand, they shorten the distance between the area south of Qiantang River and Shanghai, create traffic conditions for Zhejiang to better integrate into the Yangtze River Delta economic circle, and are conducive to the optimization of the investment environment.
Wang Zhen, a researcher at the Shanghai Academy of Social Sciences, pointed out that the improvement of traffic conditions is conducive to the adjustment of industrial structure in the Yangtze River Delta region. For example, labor-intensive industries that are sensitive to transportation costs will transfer industries and gather around Shanghai to form a more reasonable regional industrial layout.
Yu Hongsheng, a member of the Yangtze River Delta Regional Planning Comprehensive Group of the National Development and Reform Commission, said that traffic engineering construction not only opened up a new channel for the Yangtze River Delta to cross the river into the sea, but also helped to stimulate domestic demand through investment and promote the economic development of the whole region and even China under the severe situation of the current global financial crisis.
The main project of Hangzhou Qianjiang Tunnel, the world's largest diameter tunnel invested and built by Shanghai Urban Construction Tunnel Co., Ltd., started on the afternoon of 18.
20 12 learned from Hangzhou Highway Administration Bureau that the main shield machine on the east line of Qianjiang Tunnel under excavation successfully crossed the century-old flood control levee on the north bank of Qiantang River and officially headed for Qiantang River. In the next few months, all shield machines will be excavated under Qiantang River, and the east line of Qianjiang Tunnel will cross the levee on the south bank of Qiantang River and reach Xiaoshan, completing the excavation of the east line of Qianjiang Tunnel. By then, the east and west lines of Qianjiang Tunnel will be fully connected. It is estimated that all the projects of Qianjiang Tunnel will be completed by the end of 20 13.
Engineering introduction
Project overview
Qianjiang Tunnel is the control and key project of Qianjiang Passage and Wiring Project, which is generally contracted by Shanghai Urban Construction Group Tunnel Co., Ltd. in BOT mode.
Qianjiang Tunnel is 4.45 km long, in which the working well in Jiangbei is 2 1 m long and the open-cut section is 559 m (buried depth section is 327 m). The length of the tunnel in the middle of the river is 3251m; The working well in Jiangnan is 23 m long, and the open-cut section is 600 m (buried depth section is 326 m). The middle section is located about 2.5 kilometers upstream of Yan Guan Town, a famous tidal scenic spot in Haining, with the north bank in Haining and the south bank in Xiaoshan.
The project includes Jiangnan and Jiangbei working wells, open-cut sections and two river-crossing tunnels. F 15.43 m slurry balance shield is used in river-crossing tunnel construction.
engineering geology
The geological structure of Qianjiang Tunnel mainly includes ① plain fill layer, ③ 1 silty clay layer, ④2 silty clay layer, ⑤3 silty clay layer and ⑤4 silty clay layer.
The main excavation layers of Jiangnan working well and buried section are ③ 1 layer, ③ 2 layer and ④ 2 layer, all of which belong to the category of "soft soil". (3)1layer, 32nd layer silty soil and silty sand excavation are easy to cause quicksand and piping, and easy to cause sand liquefaction. ④ Plastic collapse and creep failure are easy to occur when excavating two layers of silty clay.
structural design
Circular tunnel section
(1) The key to the structural design of circular tunnel section lies in the lining structure design of shield section.
The outer diameter of Qianjiang Tunnel is 15.0 m, the inner diameter of the tunnel is 13.7 m, the segment thickness is 65 cm, and the ring width is 2.0 m. The circumferential blocks are connected by the general wedge ring method of 9+ 1, staggered joints and inclined bolts. The liner ring is connected with 38 longitudinal M30 bolts, and the block is connected with 2 circumferential M39 bolts. The cap block is inserted semi-longitudinally to improve the shear resistance of segment joints.
⑵ Waterproof design. The impermeability grade of the segment is S 12, and the crack width is not more than 0.2 mm. EPDM elastic gasket is used for waterproofing on the outer side of the segment, and polyether polyurethane waterproof strip is attached to the outer side of the elastic gasket as an auxiliary waterproof measure. Foam rubber rod and polysulfide sealant are used for caulking on the inner side of segment.
Structural design of buried pipeline section on shore
The rectangular buried section of the open-cut tunnel on the shore adopts box frame structure; The open cut rectangular section adopts U-shaped frame structure. According to the depth of foundation pit, diaphragm wall and used pile are used for foundation pit enclosure.
Electromechanical design
In electromechanical design, selecting dry-type transformer with low energy consumption, reasonably selecting transformer capacity, optimizing power distribution scheme and configuring soft start for single large-capacity electrical equipment can save energy well. The automatic compensation device of low-voltage concentrated capacitor is adopted, which improves the power factor, reduces reactive power loss and effectively saves energy. By setting lighting transition section, intelligent control lighting system, green energy-saving power regulator, high-voltage sodium lamp and LED lamp energy-saving inductance ballast, the energy consumption of lighting is reduced.
Engineering difficulties
Qianjiang Tunnel is large in scale, tight in construction period, involving many fields, strong in comprehensiveness, high in engineering quality requirements, complex in engineering structure and difficult in technology and construction.
(1) The construction site of the proposed project is a fishpond with nets. Before construction, a large amount of earthwork must be borrowed to level the ponds within the scope of the construction site.
⑵ The deepest underground diaphragm wall of working wells in Jiangnan and Jiangbei reaches 51m. How to effectively cut off the underground confined water and prevent excessive ground settlement outside the pit caused by precipitation requires corresponding technical measures.
(3) Because there is no large wharf in Qiantang River, large shield blades can only be transported by water to the wharf of Xiaoshan Power Plant in puyang river, and then by land to the construction site. Xiaoshan, the south bank of Qiantang River, belongs to the river sand deposition area, and may not meet the draft requirements of ships at low tide. There are a lot of bridges and 4 km long paths along the road. It is necessary to inspect and reinforce the bridges along the line and erect temporary steel bridges to meet the traffic requirements.
⑷ Shield construction is mostly carried out under sandy geological conditions at the bottom of Qiantang River, and the strong tide of Qiantang River will bring considerable risks to shield construction in the middle of the river.
5. A single tunnel excavation will cross the new and old flood levees on both sides of Qiantang River for four times, and the ground settlement caused by the crossing will have a certain impact on the flood levees.
[6] In the process of shield construction, a lot of qualified mud is needed, and a lot of waste mud and soil are produced at the same time. In order not to bring serious environmental impact to the surrounding areas, it is necessary to adopt the internationally advanced three-stage sludge treatment system (two-stage cyclone and three-stage centrifuge) to scientifically solidify the waste soil, so that the treated soil can be used.
Once the construction period is tight, it is necessary to adopt three-dimensional and multi-type synchronous construction methods: shield tunneling, installation of prefabricated components in place → construction of ballast blocks and grooves of prefabricated components → formwork support of brackets and lane boards, steel binding and concrete pouring → maintenance of brackets and lane boards, horizontal transportation management → formwork removal of brackets and lane boards, vehicle traffic → cast-in-place construction of anti-collision kerbs and pavement layers after tunnel stabilization →
As this project adopts 1 set of shield tunneling construction, after the east tunnel tunneling into Jiangbei working well is completed, it is necessary to translate and turn around in the receiving well, and then start the tunneling construction of the west tunnel. Therefore, a series of technical measures must be formulated to ensure the safety of shield and high-speed U-turn.
construction supervision
First of all, the risk assessment of Qianjiang Passage and River-crossing Tunnel Project is carried out, including geological conditions, river regime evolution, ground structure and regional manual activities, working well and open-cut construction, personnel safety and risk analysis of tunnel operation. Give the risk level, and put forward the main risk control measures, reduce all kinds of risks, and formulate emergency measures to achieve safe, economical and efficient management goals.
label
Qianjiang Passage and its wiring project pass through Jiaxing, Hangzhou and Shaoxing. It is the "one channel" of the main skeleton of the "two verticals, two horizontals, eighteen links, three rings and three channels" expressway in the highway and waterway transportation planning of Zhejiang Province, and it is a part of the "seven verticals" expressway from Yancheng to Shaoxing in the planning of the Yangtze River Delta metropolitan area, which plays an extremely important role in the regional highway network. Qianjiang tunnel is the control and key project of Qianjiang passage and wiring project, and it is the first large-scale river-crossing tunnel in Qiantang River basin. The completion of Qianjiang Tunnel will connect the north and south banks of Qiantang River, which is of great significance to strengthen the mutual relations and economic exchanges between important cities on the north and south banks of Qiantang River. Qianjiang Tunnel not only pioneered the tunnel construction in Qiantang River Basin.
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