Study On Long-narrow Foundation Enclosure System And Impervious System In The Environment Of Binary Geological

As the rapid development of the construction of urban subway and river-crossing tunnel in china, the development and utilization of large-scale building foundation and underground space promote the progress of deep foundation in support design and construction technology in china. However, because the engineering of deep foundation involving in complex geological condition have many uncertain factors,there are various questions in the support design and construction for foundation. Wuhan Changjiang tunnel is the first tunnel in Changjiang.the guide section,open-cut section and the section for shield well in Wuhan Changjinag tunnel in the environment of binary geological show the character of long-narrow. Doing well in the study of support system and impervious system have important reference and guiding significance.This paper carry out study relying on the foundation of Wuhan Changjiang tunnel.The main research works as follow:(1) According to the characters of controlling deformation strictly with the supports of piles pillared and wall pillared, starting with the required displacement of soil when the active earth Pressure,static earth Pressure or passive earth pressure happened, the model for the earth pressure distribution considering deformation is built, the study about earth pressure distribution in foundation is carried out.(2) According to the deformation character in force of row piles for supporting the soil behind pit, the reason for the formation of horizontal soil arch is analyzed in mechanism. Moreover, based on the character of soil in force for the three zones behind pit, which are the free zone, the zone generating soil arch and the stable zone respectively, the relative mechanical equilibrium equations and governing equations are set up, geometric parameters for soil arch and the earth pressures behind piles are derived, finally the pressures are substituted into free end method, equivalent beam method, elastic resistance method to calculate the internal force of supporting structural, and the support for row piles is designed.(3) In view of the mechanical property of statically indeterminate, in the premise of neglecting the friction effect in vertical between pile and soil and space effect, mechanical mechanism of supporting structure for double-row piles is analyzed, the finite element model of plane bar system for double-row piles which take soil effect between piles into account is set up. And centering on the key parameters of the finite element model of plane bar system for double-row piles, which are earth pressure distribution and elastic resistance coefficient, study is carried out. Finally relevant calculation program is compiled to make engineering calculation convenient.(4) Obtaining typical undisturbed cohesive soil samples from engineering site and processing into standard samples.Basic physical and mechanical features tests are carried out, as well as consolidated drained direct box shear strength tests, high pressure consolidation unloading tests and the tests in different pressures and different paths.Moreover, the results of unloading tests are analyzed in detail.Therefore,the deformation characteristics, strength characteristics and failure laws of soil in unloading response are obtained, as well as the change rule of tangent modulus in different unloading paths.In addition, the basic mechanical parameters for unloading nonlinear soil constitutive model are achieved to provide evidence for numerical calculation. (5) The results of soil unloading tests in different unloading paths are analyzed in detail. Based on the normalized study for the principal stress difference and the relation graph of axial strain, soil unloading nonlinear model are set up. And in the platform of FLAC3D which is a large finite difference soft, this model is second developed. Finally, the test section based on project is carried out relative numerical analysis calculation.(6) The impervious method for foundation and the control technology for groundwater are researched. On the basic of extensively investigating geological conditions and hydrological conditions in Wuhan area, the long-narrow foundation geological model in the environment of binary strata is generalized, percolation differential equation involving in the effect of foundation unloading is derived, relevant calculation program is compiled and improved. Moreover, by means of calculation analysis to analyze the influence of flow field and potential field of groundwater with foundation unloading, relevant groundwater control technology is put forward.(7) Centering on the uncertainty character for foundation pit, horizontal displacements of supporting structures in excavation during construction are track monitored, as well as brace forces and the deformation of surrounding buildings.And monitoring results are predicted with grey theory and time series and feedback analyzed. Besides, relevant theoretical research results are verified and improved to guide information construction.