| With the acceleration of city constructing, shield tunneling method was applied more and more widely. Traditional small diameter shields were mainly used in subway tunnel. With the continuous development of shield production technology and construction technology, shield tunneling method of super large diameter was widely used in the city highway tunnel. At present, super large diameter shield tunnel almostly adopted the slurry balance shield tunneling method. However, this kind of shield had some shortcomings especially in the central area of a city including large area demand, large amount of slurry transportation, mud spillover, large late ground settlement, etc. Thus, the super large diameter earth pressure balance machine emerged, which overcomed the disadvantage of slurry balance shield.Because of the super large diameter EPBM method has just carried out in our country, many technical problems remained unresolved. How to reduce the soil disturbance in soft soil through setting reasonable construction parameters was one of the problems. In order to find a solution, a large number of construction data and monitoring data in Shanghai Bund Road Tunnel project and the test section of the Third Yingbin Road Tunnel project were obtained to research the optimum matching of construction parameters. The research result were applied to the normal section of the Third Yingbin Road Tunnel project, and obtained good effect. This illustrated the guiding value of the method of this paper in soft soil.The major achievements in this thesis are as follows,1) Two camparisons were made in dependent on the Shanghai Bund Road Tunnel project. Firstly, the comparison of the super large diameter EPBM and super large diameter slurry shield described the value of this paper. Secondly, the comparison of the super large diameter EPBM and small diameter shield in subway construction described the necessity of the research in this thesis.2) A method for sduding soil disturbance from cybernetics was proposed by summarizing the current research methods of shield tunnel constructions. Traditional research methods were based on the continuous medium mechanics principle. The research results were not very practical for the adjustment of construction parameters because of the contradiction between the continuous medium mechanics principle and soil discontinuity during shield tunneling.3) The shield chamber was divided into four areas for analysis, and proposed that the control soil pressure should set up in the upper region to reduce the disturbance during shield tunneling. The process of chamber control pressure was researched and the rule of the control pressure building during the beginning of shield tunneling.4) The logarithmic relationships between the ground settlement and excess pore water pressure, the time of shield standstill were fittinged. Through analysis and comparison, it was found out that dissipation of excess pore water pressure was corresponding to soil disturbance around the shield in shield standstill phase. The conclusion provided a theoretical basis for judging the soil disturbance by the pore water pressure fluctuation and for construction personnel to control the soil disturbance conditions quickly.5) The influence of shield tunneling speed, shield tail grouting quantity and pressure, sport pressure of excavation surface to soil disturbance were studied. Some new characteristics of the influence of these construction parameters were found out.6) Taking the actual project as the background, based on artificial neural network and the genetic algorithm from the viewpoint of control theory, construction parameters of the super large diameter EPBM were optimized to obtain their best matching. A practical theory was put forward to study ground settlement, which took into account various factors rather than only one. This method was applied to another similar project and good results were obtained. This method was practical and had guiding value to the future constructions. |
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