Analysis Of Deformation And Stress Due To Deep Excavation Considering Different Deformation And Strength Parameters Of Soil And Space Effect Of Excavation And Retaining Structure

Nowadays, the new coastal region of Tianjin is developing greatly. On basis of the present research and the key problems in foundation pit in soft soil, the main work of this thesis is as follows:Based on summarizing the stress paths under unloading state during excavation, the soft clay samples in the new coastal region of tianjin are obtained by using thin wall sampler and a series of K0 consolidation stress path tests have been carried out according to different unloading stress ration to study the unloading deformation properties of foundation pit in different unloading stress paths. The soil calculation formula of the initial unloading modulus is induced and the values of the initial unloading modulus under different unloading stress path are given. In combination with one foundation pit project in the new coastal region of Tianjin, the general tri-axial tests and K0 consolidation stress path tests have been done in the soft soil layer of the foundation pit. The comparative analysis of the difference of the shear strength parameters in various consolidation pressures and stress paths is made and the influence of the stress path to the soft soil strength properties in the new coastal region of Tianjin is preliminaryly studied.According to the results of tri-axial tests, the finite element analysis is made by using hardening-soil model, and the influence of the values of model parameters in finite element calculation is analyzed. In combination with a deep foundation pit project in Tianjin Economic Technique Development Area, the modulus of hardening-soil model are determined and the relationship between the modulus of hardening model and the compression modulus is attempted to be found. The project is simulated by finite element method with different strengths according to direct shear consolidation fast test and regular tri-axial consolidation undrained test and K0 consolidation unloading undrained test. The influence of different strength parameters to the result of finite element calculation is analyzed and the calculation result is comprised to the result of the project monitoring.In order to find the interactional mechanism of soil and the foundation pit retaining structure ,the influence rules of the width and the slope and the height etc of the berm earth to the displacement and internal force of the retaining structure is analyzed with finite element method. The relationship between the optimal section parameters and the height of the foundation pit is found and the simplified elastic reaction method which reflects the interaction of the berm earth and the retaining structure is given. The effect of the berm earth is simulated by spring and the method of confirming the spring is given. A centrifugal model test and two typical projects are simulated by using the simplified calculation method in this thesis. The simplified calculation result is contrasted to the finite element calculation result and the monitoring result.Based on realizing the status of the earth pressure calculation theory and method, the linear and non-linear earth pressure calculation formulas considering the influence of the retaining structure displacement are found and the finite element program is made. For the first time, the influence of the linear and non-linear(trigonometric function method and hyperbola method) active region earth pressure models to the retaining structure inter force and displacement is analyzed and the effect of the parameter values is explored. Based on the analysis of foundation pit retaining plane problem, a space calculation software with linear and non-linear earth pressure and with preprocessing and postprocessing is made. By using the software , a foundation pit with different excavated depthes and a real project are calculated and analyzed, and some useful conclusions are gained.