The Working Mechanism Of Passive Pile Under Lateral Load And Instance Analysis

Asymmetric load is a common working condition in pile engineering, for example, unilateral preloading and excavation of foundation trench. If there is a soft layer under the surface of the earth, asymmetric load will result in the lateral movement of soft clay, which will increase the lateral soil pressure on the pile, and influence the stability of superstructure. So it is crucial to research the working mechanism of passive pile.Because of the complexity of the force characteristics of passive pile, there is no universal and accurate analytical model yet. A practical way is to treat the pile as a cantilever pile or grade beam, but both the two methods simplify the pile-soil interaction. The simplified model determines the accuracy of computed result. In this paper, a passive pile is divided into three parts:free-segment----the part above the ground of the pile, passive-segment----the part under the lateral pressure form liquid soft clay, and active-segment----the part under the passive-segment, and build analytical model respectively. The three parts will produce three results, which will coupled using matrix multiplication according to the continuity of the interfaces. That is the method to solve the internal force and displacement of a passive pile. Finally, two engineering projects are calculated by Fortran program to verify the validity of the method. The main achievement of this paper is:(1) A solution of the internal force and displacement of beam and grade beam in different working condition is deduced according to the force characteristics of passive pile. On the basis of different hypothesis of axial force, there are two kinds of solution of grade beam:the analytical solution when the axial force is constant, and the power series solution when the axial force is inconstant.(2) Two sets of methods are used to solve the passive pile according to different working conditions. When considering the layering of the soil, the pile----include the passive-segment and the active-segment----will be divided into some small segments in accordance with the soil layers, and every small segments will be solved by analytical method on condition that the modulus of resistance of ground is constant. When considering the yield of soil, m-method is used as the model of resistance of ground of the active-segment, and the solution is power series.(3) The solution of the internal force of bridge pile foundation with pile cap under different boundary conditions is deduced.(4) Two typical engineering projects of instability of bridge passive pile are used to verify the validity of the method in this paper, and reliable results have obtained.