Study On Soil Deformation Analysis Induced By Shield Tunnel

Shield tunneling is more and more applied during utilizing and exploiture of city underground space, with the development of urbanization and maturation of shield construction technique in China. It's well-known that, shield tunneling has a unique excellence. It has the extensive applicability the little influence to the normal enginery of the city satisfying the requirements of peculiar engineering and so on. At the same time, shield tunneling would induce soil movement inevitably. As we always focused, the construction or buried pipelines around it would damaged while the ground displacement is big enough.In this dissertation, some researches were made about the movement caused by shield construction. The grope of shield tunnel ground maximal settlement during construction, the three-dimensional analytic solution of the soil displacement, the post-construction question of the tunnel engineering and predicting the movements of the shield tunnel with the radial-basis function neural network theory. I brought forward my viewpoints in the following aspects in my dissertation.(1) The academic supporting for the most important parameter S_max in Peck formula, which is the classical shield tunnel settlement prediction formula, is attempted to get in this dissertation. A simple model was gained based on the practical construction process, and the analytic formula was deduced then. It was shown in analytical calculation that, the precision prediction of maximal settlement using this formula can satisfy the engineering precision need.(2) Sagaseta got the soil loss distributing formula along the forward direction using mirror image method. Combining the result, Loganathan formula (planar soil movement formula) was expanded to three-Dimensional analytic formula of the soil displacement. Then, it is very easy to get the soil movement of arbitrary point induced by shield construction. And the movement involves the vertical settlement and the horizontal displacement which perpendicular to the tunnel direction. And the horizontal displacement is the emphasis in this dissertation.It was shown in analytical calculation that, the vertical settlement prediction value has a good consistency with the field data, the horizontal prediction value has a little difference yet at certain points. And the attitude deviation of the shield advancing partly overbreak and underbreak maybe are the possible reasons for the difference.(3) In this dissertation, other 8 mathematic prediction models were collected, which were applied in the post-construction settlement prediction in highway roadbeds and building foundations. And these 8 models were applied in shield tunnel long-term settlement prediction for the first time. Included the hyperbola model, these 9 models were checked up with 11 examples calculation. Based on the results, and according to the degree of approaching the actual data, the 10 models were classified to 3 kinds. It was advised that, the first kind (involving the DENG Ying-er model and the Mmrgan—Mercer—Flodin model) can be applied to the long-term settlement prediction in tunnel engineering.(4) The program, for the prediction the long-term settlement caused by shield tunnel, was made with Matlab software, and taking advance of the radical-basis function network. In operation, the training (the fitness) and the simulating (the prediction) were combined, and the precise prediction was got as a result then. It was shown after 11 analytical calculation examples that, a very satisfactory result of the the shield settlement prediction would gain by the artificial neural network.