The Technique Research Of The Supporting Technics For Deep Foundation In Tianjin Subway

At present base hole project has become a hot point in the rock soil project that the popular pay close attention to. It not only is a difficult point whose technology is too complicated and hard comprehensive, but also is a focus which can improve project quality and reduce project accident.Dark base hole project have distinctly regionality and individual character in the geological environment of the different geological condition and different hydrological condition. Even in the base hole project of different areas of the same city there is a difference. In addition, dark base hole project has related to not only the geological condition and hydrological condition, but also the position of buildings, structures and underground facility in close proximity to the base hole, the ability of resisting deformation, the project importance, local condition around and so on.In recent years, there is more and more construction of the skyscrapers and subways in Tianjin. Because Tianjin city is in close to Bohai Sea, the underground water is abundant and the depth is shallow. The soil is mainly made of mixing soil, powder clay, powder soil and silt powder clay. How to carry on dark base hole in higher coastal soft soil area has become a thorny problem that the designers and constructors have to face. Facing the condition and combining the dark base hole of Huayuan subway station in Line 3rd of Tianjin, the paper focuses on the mainprotecting structure of bark base hole——bored lock piles, which is a new-typeunderground continuous wall and is on discussing of theory and practical analyzing while excavating in the deep base hole, the paper optimises the construction of steel supporting and the waist roof beam, etc. No matter social benefit or economic benefits, the results are very remarkable, the concrete contents are as follows:First, the construction of the bored lock piles. Because the bored lock piles are a kind of new pattern and new technics in the dark base hole supporting structure of the domestic underground project, by the compare of the structure schemes, the main protecting structure of the dark base holes all adopts the pored lock piles and its biggest depth is 32.8metres, which is met for the first time in the country. The paper draws in detail on the construction of the bored lock, quality control of the key technology, the common accident treating method in the construction and etc.Second, checking computations of many dashes of steel supporting and the optimization of steel supporting waist beam. Because the depth of the dark base hole reaches 18.5 meters, and there are four to five lines of steel supporting in original design, even taking turns with construction, the period is so long and thecost is so expensive.The paper carries on checking computations respectively with the flexibility base beam law, which has reduced the project cost as well and has shortened the time limit for a project.Through the research of the paper, the writer hopes the bored lock piles can be used widely in the soft land of the coastal area in the future, offering practical experience for the new-type deep base hole supporting structure and a good example to optimize design and construction of dark base hole project in Tianjin, thus it perfects the pattern of the dark hole protecting structure constantly ,and promotes to develop the dark base hole theory in the direction with reasonable science, in order to reduce the emergence of the project accident and obtain the good economic benefits and social benefit.