Analysis Of Seepage And Deformation Of Deep Excavation Of Foundation Pit

During the excavation of foundation pit, due to the wide variation in water lever, the huge head fall should result in drastic flow of the ground water, which will bring about a full influence on the deformation of the retaining wall and on the surrounding structures in a large-scale range. In the case of the solution of the problem, the effect of seepage, such as seepage force, should be paid a great attention to. Aiming at this problem in paper, the following contents are studied in detail:(1) Development status, chiefly existent problems, common studying means and numerical methods of foundation pit project are introduced briefly. Meanwhile superiority of applying finite element method to problems of seepage and deformation caused by water decreasing in foundation pit is pointed out.(2) By means of four nodal equal element, the finite element equations of constant and inconstant seepage are deduced first. Based on the corresponding two-dimensional finite element, program is compiled. And all kinds of boundary conditions are discussed in program, including disposing method of free face etc. Seepage field's characteristics of the foundation pit are addressed in emphasis.(3) FEM basic theory of foundation pit excavation stimulation is expounded, numerical model and method of construction simulation are determinated, which includes simplification of two -dimension problem and constitutive model of soil mass i.e. constitutive model of Duncan-Chang hyperbola model, numerical ways of initial situ stress, stimulation of equal nodal load of foundation pit excavation, nonlinear solutions of basic equations, FEM disposing of inner supporting and pre-axial force etc. Further FEM code of stimulation of foundation pit excavation is compiled.(4) FEM analysis on foundation pit of Nanjing Zhujianglu Subway station, deformational laws of foundation pit are concluded within three functions of seepage, no seepage, interaction of seepage and dryness. Meanwhile distributive laws of seepage force caused by every grade of water decreasing are still educed.(5) The effect of the supporting system on the deformation of the retaining structure is studied in detail.(6) The ratio of the maximum value of the ground surface settlement and the horizontal displacement of the retaining structure has been found to be constant in the condition of an universal clay soil, steel bracing, seepage force etc.