Research On The Surface Settlement Estimation Methods Of Deep Foundation Pit On The Interurban Railway

The demand for transportation has increased massively with the rapid development of society and economy. Major cities compete to develop and construct rail transit in order to meet multi-level travel demands and optimize the spatial layout, to promote the development and utilization of land as well as build a perfect spatial system, besides, to achieve the needs of national sustainable development strategy. And the construction of underground station can’t be separated from foundation pit engineering which should take note of deformation of surrounding buildings due to the restrictions of surrounding environment. Now the design for support of foundation pit has become from intensity control to deformation control. Under the premise of ensuring the stability of the foundation pit, and with the goal of controlling deformation, how to make rational support scheme and to realize the target that the support structure corresponds to the requirements of surrounding environment on the deformation of foundation pit according to the hydrogeological conditions of the site, the engineering geological conditions and environmental conditions, has become the development tendency of the design for support structure of foundation pit. Based on the above reasons, the thesis focuses on the subject of deformation control design to study the space effect of foundation pit, deformation control measures and surface settlement estimation methods by adopting numerical analysis and theoretical analysis and so on. And the main research contents and results are as follows:(1) The empirical method of surface settlement is mainly studied in this part:first in the ground loss method, the ratio of the horizontal displacement area of support structure and the ground vertical area has been studied. And then by introducing Poisson’s ratio parameters, the formula of surface settlement envelope area has been deduced and, the formula of area ratio under the ground of monolayer and multilayer has been given.(2) The theoretical method of surface settlement is mainly studied in this part. The change of soil effective stress caused by precipitation has been analyzed in detail and then the formula of effective stress has been deduced. Besides, through introducing stochastic medium theory and considering some influencing factors such as earth interaction and so on, the theoretical formula of surface settlement has been gotten.(3) By using FLAC3D software, the3D model of station’s narrow foundation pit has been established, and the space effect of that has been analyzed well. Besides, the spatial distribution rule and pit angle effect of support structure deformation have been studied. Then, the influence of segmentation excavation length and the block excavation upon foundation pit deformation have been studied as well. Last, the author puts forward relevant deformation control measures according to the analysis on the space effect of foundation pit.