Research On The Deformation Of Metro Shield Tunnel During Operation

With the gradual expansion of cities, urban population continues to increase, ground transportation has become increasingly busy and crowded. Subway projects are developing rapidly in many cities. However, a series of engineering problems caused by this attracted highly attention of experts and engineers nationwide and abroad. Especially for subway tunnels in the coastal soft soil area, which produced long term excessive settlement deformation in the process of operation is one of the main problems currently existing in this region. The thesis takes shield tunnel as the research objective, using finite element analysis and empirical fitting formula calculation methods, combined with actual working conditions of Shanghai trial operation interval shield tunnel as the research background, to focus analysis the long term settlement issues of tunnel-soil structure caused by the train vibration load. According to the actual situation, study to the influence of long term settlement of shield tunnel under different working conditions. Specific work of this thesis reads as follows:(1) It systematically sums up the research status and development trend on long term settlement deformation of shield tunnel in vibration load of train. The stress-strain relationships of soil material are deeply analyzed by using the theory of soil plasticity mechanics. In combination with the constitutive models of several commonly used in ABAQUS finite element software, through the analysis of theoretical derivation and meaning of parameters, obtaining the Limitations and scope of application of constitutive models.(2) The generation and mechanism of train vibration load are introduced in detail, and the model of train track interaction is simplified according to the characteristics of train vibration load. The dynamic load of each wheel is simplified as series of vertical concentrated load with time variation. Combined with the design parameters of the vehicle and track, the exciting force corresponding to the irregularity management value is used, and obtaining the time history curve of the train vibration load change with time. According to the actual operation of the train in the tunnel, the application mode and action time of the vibration load of the train are simulated by using the method of reasonable simplification.(3) For the inadequacies existing in the simulation of long term settlement of metro shield tunnel, the thesis uses three dimensional modeling analysis and empirical fitting formula based on anisotropic non drainage ultimate strength. Using with the method of predicting the soil settlement of the crossing-river highway tunnel to calculate the soil settlement deformation of metro shield tunnel. By modeling the existing practical engineering analysis, and with the previous simulation results and the actual monitoring data were compared to verify the optimization method to enhance the accuracy of computation, for calculating the subway shield tunnel under the train vibration load settlement problem providing a more reasonable and effective method.(4) According to the actual engineering geological conditions, simulation the settlement of Shanghai trial operation metro shield tunnel, from the tunnel under lying layer and the tunnel lining thickness and other factors research, deeply analysis the effect of the dynamic load on the long term settlement deformation of tunnel. Studies have shown that by cumulative plastic deformation caused by tunnel settlement accounts for the total settlement value of about 75% and basically not changed with the lining thickness and soil conditions change. Compared to the lining thickness are main factors of the tunnel settlement deformation, weak underlying layer of tunnel settlement deformation effect is more obvious. When the tunnel soil structure in the presence of weak underlying stratum, the settlement deformation rate and value will increase accordingly and tunnel settlement deformation tends to be relatively stable time will increase too.