The Environmental Influence Analysis Of Shield Tunneling In Watered Sandy Stratum

The problems of environment in urban would be caused by tunnel construction, such as ground subsidence, pipe line damage, building deformation etc.,even the confusion of the society may be aroused. As well as we known the shield tunneling technology is a method which environment influence less than others, but for the lack of construction control experience, the environment accidents occurs at times. They were many factors by which environment were affected during shield tunneling construction. It is a particularly complicated problem to analyze the ground subsidence and prop pressure change when shield tunneling pass through Saturated Sandy Stratum. Furthermore the influence on environment by the ground subsidence and prop pressure change is another problem. So the in-depth study on this problem have important significance for the design and construction of shield tunnel and protection of urban environmental. Based on the shield tunneling mathematical model, a model was erected to simulate the process of shield tunneling work in consideration of Fluid-Solid coupling interaction. The behavior and the environment influence of a metro construction site was simulated by FLAC3D Program Compared with the measured result, it was shown that the calculation results is reasonable.With the above calculation method and model, the law of the influence on environment by shield tunneling construction with different parameters and conditions was studied. Some valuable conclusion was achieved and those conclusion have the significance for the guidance to the shield tunneling construction. The main research work of this paper is as follow:1. The development of shield construction technology and its application in China was described. The mechanism of soil-disturbing and the range of the ground subsidence were analyzed resulting from the tunnel construction. Also the research methods about disturbance of surrounding soil caused by shield tunneling were generalized.2. The characteristic of FLAC3D program was introduced. And the method of fluid-saturated solid coupling numerical simulation and the principles and process of the simulation was illustrated.3. A shield model which combined with every kind of impact factors was established based on the analysis of characteristic of construction and mechanical behavior of shield tunnel. 4. According to the shield drivage process of a 90 meters long tunnel with Saturated Sandy Stratum conditions in Line 2 Shenzhen Metro project, the law of prop pressure changes and ground subsidence which caused by excavation was calculated with principle of effictive stress in consideration of Fluid-solid Coupling interaction. Compared the calculated result and the measurement results, the value were similar and tendency got good agreement. So it was confirmed that the numerical simulation method and the parameter which was used in the model was rational.5. With the calculation model and method above, the law of impaction on the environment from the difference construction conditions and driving parameters was simulated. According to the above study, some new conclusion was drawn and the new achievement of this study can be used as guide to the construction of shield tunneling in similar stratum.