Analysis Of A Single Pile And Pile Groups Subjected To Axial Loads In Layered Soils

The foundation soil is a sedimentary deposit and a non-homogeneous medium. Usually in the vertical direction, the foundation soil is evenly divided into several layers or the elastic modulus of soil is the continuous function of the foundation depth. In analyzing the pile-foundation interaction, the non-homogeneous properties of the foundation should be considered.This paper presents the numerical method for analyzing the pile-foundation interaction considering the non-homogeneous properties of the foundation soil. In the proposed numerical method, the generalized Kelvin fundamental solutions of layered solids are applied. The interface coordination of stress and displacement has been considered in the generalized Kelvin solutions, therefore the integral along the interface can be avoided. Thus, a single pile and pile groups in non-homogeneous soils can be easily analyzed.The pile is discretized into cylinder and circular elements, and the corresponding soil foundation is also discretized into the elements of the same amount and type. First of all, based on the generalized Kelvin solutions, the equations of stress and displacements are established for piles and soil foundation, respectively. The beam theory is used to establish the pile equation of stress and displacements, and the fundamental solutions of layered solids are used to establish the pile equation. Then, the global equation for obtaining stress and displacements of pile-foundation interaction are presented by using displacement compatibility. The corresponding programs are written in Fortran 90. The verification of the proposed numerical methods is executed by analyzing the three examples of a single pile and pile groups. It can be found that the results obtained by the proposed method are satisfactory. Using the numerical method, the impact of main factors on a single pile and pile groups in the layered soil foundation are further analyzed in detail. Some conclusions of linear elastic conditions are obtained, which can be used for pile design and constructions.With the loads on the pile increasing, the lateral shear stresses along the pile increase. The slipping along the interface of the pile-foundation occurs when the lateral shear stresses are equal to the critical values of the pile-foundation interface. Considering this phenomenon, the proposed numerical method is modified. The verifications are executed by two examples. It can be shown that the proposed method is effective. The impact of main factors on a single pile, such as, the hard depth and the end expanding, is calculated by using this method. Some conclusions are obtained, which can be used for design and constructions of pile foundation.