1. 1 Introduction Shield is actually the abbreviation of shield machine. It is a machine with the same cross-sectional shape as the tunnel, slightly larger in size, with built-in digging and dumping machines and its own protective shell. A complete tunnel construction method with shield as the core is called shield construction method, and the general situation is shown in figure 1. 1. The idea of shield method was born in England at the beginning of19th century, and it has a history of 200 years. Before the appearance of shield method, tunnel construction mainly relied on excavation method. But as far as urban tunnel construction is concerned, the excavation method is limited by topography, landforms and environmental conditions; The excavation method brings great inconvenience to urban traffic; The ground settlement caused by excavation is large; Noise and vibration of construction machinery; Many unfavorable factors such as environmental pollution caused by construction. Relatively speaking, shield method does not have these defects, so people attach great importance to it and develop rapidly. People not only developed the shield construction method in soft soil, but also developed the shield construction method suitable for pebble stratum and other strata. In addition, careful research and development have been carried out in improving safety, improving engineering quality, shortening construction period and reducing cost, and great success has been achieved. At present, shield method has established a stable leading position in urban tunnel construction technology and has become an indispensable general tunnel construction technology.
At present, tunnel science and technology workers are working on more advanced fully mechanized computer-controlled intelligent shield construction method, which is suitable for the research and development of shield construction method with large underground depth, special section and function.
1.2 development history and present situation of shield tunnel18th century, the British put forward the idea of building a tunnel across the Thames in the London underground, and discussed the specific excavation methods and the use of machinery. 1798, I began to hope to realize this idea, but my plan was frustrated because the shaft could not be dug to a predetermined depth. However, the idea of crossing the Thames tunnel is growing. Four years later, Torevix decided to build a tunnel connecting the two sides in another location, and then the project started again. Various difficulties have been overcome in the construction. When the excavation reached the last 30m, the excavation face was suddenly flooded, and the idea of crossing the Thames was dashed again. The project lasted for five years from the start to the forced termination. The plan to cross the Thames did not make significant progress in the next 10 year.
18 18 years, brunell observed the process of insects eroding the bottom plate of wooden boats, and got some enlightenment. On this basis, he proposed a shield construction method and obtained a patent. This is the prototype of the so-called open hand-dug shield. Brunell was very confident in his new construction method, and in 1823, he drew up a plan to build another highway tunnel on both sides of the Thames in London. Subsequently, the plan was confirmed by the then Congress, and the project started on 1825. The length of the tunnel is 458m, and the cross section of the tunnel is11.4m× 6.8m. The project is progressing smoothly, but it was forced to stop due to ground subsidence. But brunell didn't lose heart. He summed up the lessons of failure, improved the shield for seven years, and then restarted the project at 1834. After seven years of careful construction, the tunnel was finally completed at 184 1. Brunell used a square cast iron frame shield in the tunnel. It has been 20 years since brunell challenged the Thames Tunnel to its completion. Through unremitting efforts, brunell overcame all kinds of difficulties and finally won. At this time, he was 72 years old. Brunell's contribution to shield construction method is extremely outstanding, which is the unanimous opinion of later generations.
Since brunell's square shield, the technology of shield has been improving for 23 years. By 1869, the second tunnel across the Thames was built, with a circular section for the first time, with an outer diameter of 2. 18m and a length of 402m. Burlow and Great are in charge of this project. Great adopted a newly developed circular shield and used cast iron sector blocks until the end of tunnel excavation without any accident. Then Great succeeded in the construction of the South London Railway Tunnel from 65438 to 0887, which laid the foundation for the current shield construction. Eighty years have passed since Torevix's initial failures and setbacks, the introduction of Brunel shield construction method, and the improvement of Great shield construction method.
/kloc-from the end of 0/9 to the middle of the 20th century, the shield method was introduced to the United States, France, Germany, Japan, the Soviet Union and other countries, and developed to varying degrees. The United States first developed a closed shield in 1892; In the same year, a sewage tunnel was built in Paris, France with concrete segments; From 1896 to 1899, Germany built the Berlin tunnel with steel pipe blocks. 19 13 the elbe river tunnel with horseshoe-shaped section was built in Germany; 19 17 Japan used shield method to build the national railway feather crossing line, but it was stopped because of poor geological conditions; 193 1 year, the Soviet union built the Yingdun Moscow subway tunnel, and chemical grouting and freezing methods were adopted in the construction. 1939, Japan built a closed tunnel with a diameter of 7m with a hand-dug circular shield; 1948 Soviet Union builds Leningrad subway tunnel; 1954 a φ2.6m circular shield drainage tunnel was built in Fuxin, China. 1957 shield sewage tunnels of φ2m and 2.6m were built in Beijing, China. 1957, Japan built the Tokyo subway tunnel with a closed shield. In a word, although the shield method has also made progress in the past 50~60 years, the characteristic of this period is that the shield method has been popularized all over the world.
From 1960s to 1980s, the shield method has been continuously developed and improved, and remarkable achievements have been made. From 65438 to 0960, drum excavators were used in London, England. In the same year, new york used hydraulic jack shield for the first time; 1964 slurry shield is used for the first time in Saitama tunnel. 1969, Japan first implemented slurry pressure shield construction in Tokyo; 1972 Japan successfully developed earth pressure shield; 1975, Japan successfully started the earth pressure shield; 1978 Japan has successfully developed a high-concentration slurry shield; 198 1 year, Japan successfully developed the bubble shield; 1982, ECL method was successfully developed in Japan; 1988, Japan successfully developed the slurry double-circle overlapping shield construction method; 1989, Japan successfully developed high-pressure construction method and grouting shield construction method. In a word, this period is characterized by the development of a variety of new shield construction methods, mainly slurry shield construction method and earth pressure shield construction method.
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