Φ 9.1m slurry shield is pushed out from a shaft 70m deep underground. Japan's deepest submarine tunnel of Tokyo Gas Fan Island Factory excavated 530 meters in the submarine stratum, and then reached the submarine shaft, and the shield machine stopped instantly.
This shield tunneling project was completed in 6 months from March 6, 1995 to September 8, 1995, including preparations for shaft construction, shaft sinking, shield launching and protection. Under the high water pressure of 700KPa, a completely watertight shield tunnel was completed in 2 1 month, which is another proof that Japanese shield construction technology is at the world-class level.
The origin of shield tunneling was in 18 18, and the British M·I· Brueger used a "shield" to push out the retaining structure in a working pit with a depth of 2 1m on the Thames in London. The back wall of the working pit is used as the supporting wall, and the used screw jack is used as the propulsion power to make this "shield". On the way, it was interrupted by the collapse of riverbed soil and flooding. Later, the tunnel was actually built for more than 20 years. At this time, as the founder of the shield machine, Bruhuangge has become a 72-year-old man. Today, the development of shield construction method is due to the enthusiasm of this two people.
Since then, in the South London Railway Tunnel Project from 65438 to 0887, pneumatic shield method was also used to build the foundation of shield method.
1890 era, although the United States, Germany, France and other countries used shield method in tunnel construction. Half shield (roof shield), oval shield, horseshoe shield and rectangular shield are also used.
In Japan, by learning the technology from Europe and America, the shield method was adopted in the construction of underground railways and sewers around 1940, and the closed construction method was developed after 1970, and it developed by leaps and bounds. 1989 earth pressure shield machine made in Japan was adopted in the tunnel project across the Anglo-French Channel, which is ahead of the world so far.
The following introduces the introduction and development of Japanese shield construction method, and the prospect in the future.
Japanese shield construction method
Introduction and development of shield construction method
The first successful shield construction method in Japan is the closed subsea tunnel project of China Railway (1939 ~ 1944). In the bad foundation of our company, the ascending line is 405m and the descending line is 725m m. The φ7.2m manual excavation shield machine is adopted, and the pneumatic construction method and chemical liquid grouting method are adopted for construction. Through this project, it can be considered that the technology of Japanese shield construction method has been established.
1953' s Guanmen Highway Tunnel and 1957' s Didu Expressway Line 4' s nagatacho No.2 Work Area used the roof shield. In addition, the Desperate Mountain Tunnel of Nagoya Metro adopts manual excavation shield and pneumatic construction method.
Later, because 1964 faced the project of Tokyo Olympic Games, with the high economic growth, the construction of urban facilities was required to increase sharply, and the public hazards brought by construction projects were sometimes obvious. In previous urban tunnels, cut and cover was replaced by manual excavation shield method. During this period, with shield tunneling, dewatering method and pneumatic method are used as countermeasures to treat groundwater, while auxiliary methods such as chemical liquid grouting method are used as measures to treat foundation settlement.
While popularizing the shield construction method, we hope to develop a shield construction method that can shorten the construction period, save labor and deal with complex foundation, and the mechanical tunneling shield construction method is the first new shield used in Osaka 1963 Daejeon water pipeline (φ2.6m, length 227m). In the second year, in Osaka underground railway project, the mechanical tunneling construction method with a diameter of 6.97 m and a tunneling length of 668.4m was adopted, and various manufacturers and companies devoted themselves to the development of mechanical tunneling shield machines and pushed them to the practical stage.
2. Development of closed shield construction method
As air pressure construction method or chemical grouting method is used as auxiliary construction method, oxygen shortage accident, chemical mud damage accident or tunnel fire accident may occur. In the process of exploring the countermeasures of these accidents, the construction methods of slurry shield and earth pressure shield appeared.
The principle of slurry shield was conceived by the French company Camnoperonadu in 196 1, and the slurry shield method was adopted in the diversion tunnel (φ3. 1m, length 3 12m) of the main line project of Shenlan No.1 work area of Imperial Capital Expressway Traffic Camp in Japan in 1967. Mud shield construction method is to seal the cutterhead part of mechanized shield, press the mud to the excavation surface with partition wall, and transport the excavated soil slag away in the form of fluid with mud discharge valve. As a large tunnel section, in 1969, the Haneda Tunnel of Japan Railway Construction Corporation, which runs through the Morisaki Canal, adopted a line project with a length of Φ 7.29 m and a length of 856m×2, which attracted great attention from foreign people.
In addition, in 1974, the earth pressure shield was independently developed by Japan. In this shield construction method, a partition wall is also set behind the cutter head of the mechanized shield machine, the soil residue is discharged by a screw conveyor, and the excavated soil in the closed bin is stirred into mud by a mixing and stirring mechanism, and the stability of the excavation surface is obtained by a given pressure. As an improved earth pressure shield construction method, additional materials (mud-adding materials and mud materials) are injected into the closed chamber of the cutter head, and the pressurized shield construction method with mixing impeller assisting mixed soil is developed. The possible application scope of earth pressure shield construction method is gradually expanding. Earth pressure shield method was first used in the water pipe construction project of Tokyo Waterway Bureau. As an additive material, bubble (foam) shield method is used to improve the fluidity and water sealing performance of excavated soil.
Closed shield construction methods such as mud and earth pressure have improved the atmospheric working environment in the construction tunnel, and there are no more problems such as air leakage and lack of oxygen, which has become the mainstream of shield construction methods in the future.
3. Diversification of shield construction methods
Due to the practicality of closed shield construction method, the influence on the surrounding environment such as the stability of excavation face and foundation settlement becomes smaller, and shield construction method has become the main force to deal with the construction of large-scale tunnels such as subways, sewers, power communication, roads and underground ditches under unfavorable construction conditions.
In addition, in the second half of 1980s, the corresponding demands for the scale, shape, linearity, automation, labor saving and cost reduction of these tunnels have become the driving force of technical competition between general contractors and manufacturers.
(1) large section
In order to overcome the stability of the excavation face and the efficiency of the combination of materials, machinery and materials, the φ 14. 14m road crossing Tokyo Bay was taken as the starting point to build large-diameter tunnels such as railways, highways and underground rivers.
(2) The depth is large
Because the shallow underground space in the city is occupied by existing structures, it is necessary to deepen the new tunnel, which will become a tunnel with a depth of 60 ~ 70 m, and it is necessary to improve the bearing capacity and durability of the shield machine and segment, which is a necessary condition for large depth and high water pressure construction.
(3) Long distance
It is difficult to guarantee the land for the shaft in the densely populated downtown area. In order to reduce the cost, through the effective use of shield machine and other functions, it is required to use 1 shield machine for long-distance tunneling. In this case, it has become a topic such as the durability of shield machine, the replacement technology of cutting bit, the treatment equipment for digging and cutting soil, and the equipment for transporting materials and equipment to the excavation surface at high speed. The performance of the project with a construction length of 6.5km is emerging.
(4) section optimization
Usually, the project cost is directly proportional to the excavation section. In addition, due to the limitation of land use, a tunnel can meet the purpose of use and minimize the cross-sectional area. According to this need, MF, DOT and H have been developed continuously.
(5) Docking technology between tunnel lining and underground.
As one of the technical developments to shorten the construction period and reduce the cost, ECL method has been developed. This method does not use prefabricated segment lining blocks, but directly sets templates in the shield and pours tunnel lining on site. In this case, the shield machines of both sides will carry out shield docking technology in the stratum, and develop projects such as soil freezing method and MSD method.
4. Overseas assessment
1Several main sections of the 49km-long tunnel between Britain and France, which was opened in May, 1994, have comprehensively used Japanese shield machines in design, manufacture and maintenance.
They are all excellent construction achievements, and Japanese shield technology and the efforts of relevant personnel who have been engaged in this field for a long time have become the targets of overseas evaluation.
Future technical topics and prospects
According to the development of large-depth and large-section tunnel excavation technology represented by the channel tunnel between Britain and France or the cross-harbour tunnel across Tokyo Bay, and the background that the land for infrastructure in the capital circle is difficult to guarantee, the Special Treatment Measures for the Use of Large-depth Underground Public Works was formulated in May 2000, and the underground development technology once again attracted people's attention.
Especially, we have great expectations for the shield construction of long underground structures such as railways and highways. Needless to say, in the future, we look forward to the technological development with the goal of safe, high-speed and low-cost construction under the premise of ensuring quality. Specifically, the following technical topics can be cited.
Large depth (sealing of shield machine, methods of starting and arriving, soil removal mechanism, etc.). )
Large section (direction control of shield machine, segment joint, assembly method ...)
Long-distance transportation (transporting excavated soil and debris, transporting blocks, repairing and replacing cutting heads, safety and hygiene of operators ...)
Treatment of formation obstacles (excluding foundation piles, exile wood sections, etc.). Original structure ...)
Downtown construction (compact temporary facilities on the ground to reduce noise and vibration ...)
Recently, as a new shield construction method, we must promote the idea of several shields as a whole, so that the underground road ramp can be bifurcated at will and other reasonable construction, and we can see the harbinger of high technology of shield construction method. For the needs of society, technicians are expected to make further research results.
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