Stability Analysis Of Soil Body In Slurry Shield Tunneling And Test Research

With the development of urbanization, it is necessary that traffic tunnels like subway become more and more important because of increasingly crowded traffic, and modern city requires higher demands on underground traffic tunnels not only in magnitude and also in quality. There consists of many problems in shield tunneling especially slurry shield tunneling contrast to the fast development and great demands of shield tunnels, in which the most important is the unstable condition of soil body. So it is of practice demand and of great theoretical significance to explore the stability rule of soil body of the slurry shield tunneling.Bases on Project East Fu-xing Road tunneling, Project Xiang-yin Road tunneling and Project South Sitsang East Road tunneling, the rules of face stability , the soil collapse after the shield tail pulled out of segment and the tunnel floating, stability of the soil body around starting shaft are investigated. The major works and results of this dissertation are as follows:(1) The microcosmic mechanism of slurry balancing face, the formation factor and course of filtercake are analyzed; Based on the unstable face forms, the ameliorated wedge model is set up. The ameliorated wedge model can synthetically consists of influences of shape of the sliding face, slurry penetrating face soil and excess pore pressure. Parameter sensitivity is analyzed about the ameliorated wedge model.(2) It is found that the polymer and the Mixed Metal Hydroxide could depress the dispersibility of the clay, reinforce the stability of the sand and improve the characters of the slurry, then developed the Polymer-MMH Shield Slurry through material choice test, serosity-make ability test, anti-pollution test and restraining dispersive drillings recycling test. Used in Project East Fuxing Road Slurry Shield Tunneling, a filtercake with low porosity, compact and larger thickness was made. So the Polymer-MMH Shield Slurry System have the good utility, and can be extensively applied in the construction of the large-diameter slurry shield tunnel.(3) 10 synchronous grout proportioning tests are carried on, and tests on slump, consistency, density, bleeding rate, shrinkage ratio and pH value. According to this 3 synchronous grout proportions with good groutability are selected. After that, simple shear tests; consolidation tests are carried to determine the cohesion c, internal friction angleφ, the compression index a_ν12 and modulus of compressibility E_s1-2, and also uniaxial compression tests about the grout with curing age of 3d,7d,28d are carried to determine uniaxial compression strength at different curing age. Based on results of the first phase, tests are carried to determine every index of the grout with additives, and the better synchronous grout proportion is to be applied in the field.(4) The reasons of soil over shield tail losing stability and influencing factors of slurry shield tunnel floating are analyzed. A simplified elastic base beam for floating of slurry shield tunnel is put forword, and the longitudinal rigidity, foundation modulus and buoyancy to tunnel are determined respectively. It shows good effect with the elected grout to anti uplifting contrasting to the monitoring data in Project Xiang-yin Road tunneling. Lastly some effective meseases are put forward to control the floating of slurry shield tunnel.(5) The reinforcement principle, reinforcement range and common reinforcement methods are introduced briefly. It is to be analyzed the strength and stability demands of the reinforced soil body with thin board strength theory, slide theory and limit balancing theory, and checking computations are carried on a domestic slurry shield tunneling project, the computation results are compared to the FEM results.