| In recent years, with the rising of water diversion project, water diversion tunnel because it can guarantee a good quality and become the main building engineering. In the tunnel construction process often encounter unforeseen complex geological problems, which makes the traditional construction method, it is very difficult to solve. Artificial freezing method because of its high security, strong adaptability of the structure and water resisting and green non pollution and other advantages, is widely used in underground space. In Yintao project in Gansu largest water diversion project-a period of general main canal water supply 7# tunnel water in loose sandstone section as the research background, aiming at the construction of freezing method, the use of large-scale nonlinear finite element program ANSYS focus on the analysis of the distribution of stress field and displacement field distribution of the temperature field changes in the freezing process and freezing curtain formed and in the excavation process of the frozen curtain. Thus it provides the reference for the control of temperature and time during freezing process, for the tunnel in the selection line layout, structure design and construction of excavation and supporting provide scientific and technological support, strengthen the tunnel disaster forecast and disaster prevention and mitigation response capabilities, to ensure the engineering safety, smooth and normal construction and has great significance in saving investment.This article mainly has the following research work and conclusion:1. In a comprehensive analysis of engineering geological works cited Tao decades of exploration data and 7# tunnel engineering geological condition of reinforcing foundation Tao Kan tunnel surrounding rock engineering tunnel section, the Tao River Diversion Project areas especially the basic geological data of 7# tunnel water in loose sandstone section where the project regional geological environment background, geological structure, topography and geomorphology, stratum lithology and engineering geological parameters were analyzed, that is the result of the model analysis parameters calculation.2. Based on the consideration of thermal solid coupling theory of phase change, using the large finite element analysis software ANSYS, the formation process of change, the diversion tunnel freezing temperature field during freezing curtain are analyzed, calculated the frozen soil curtain fully formed the time required. The results showed that:the positive 50 day freeze frozen soil curtain to design the thickness of 2.5m, the average temperature of-10 DEG C to reach the design value.3. Numerical simulation of excavation process. Stress field and displacement field distribution of temperature field distribution of frozen soil curtain and permafrost temperature and thickness in the design of curtain, and its pressure, tensile, shear stress and determine the location of the extreme. The results showed that:in the process of the excavation of frozen soil curtain pull, pressure, maximum shear stress are respectively 2.88MPa,0.15MPa and 0.97MPa, accord with the design requirements, the calculated value relative to the safety coefficient design values were 2,13 and 1.5.4. Combined with field monitoring data, analyzes the formation mechanism, the rule of temperature change and frozen frozen during the results show that:the frozen soil curtain produced a small displacement, can effectively maintain the formation stability, provide good working space for construction. Finally puts forward some effective measures and suggestions. |
PDF Full Text Request