Study On Behavior Of Single Pile Under Lateral Loading

The majority of piles are designed to support vertical loads which are created by the weights of themselves and superstructures. However, in many cases, piles are also subjected to the lateral loads created by waves, wind, earthquake, earth pressures, impacts of ships, etc. With the fast increase of the economy in our country, the laterally loaded piles are used more and more widely, but there are still too many questions needed to be solved in the design and calculation. Therefore, to investigate the behavior of piles under lateral loads and the calculation methods is very important no matter in theory or in application. Based on the systematic overview of theoretical analyses, numerical analyses, lab tests and field studies, the main original works and obtained achievements in this paper are as follows:1. Based on the subgrade reaction method, the differential equation for the pile deflection under lateral loads is deduced, in which the coefficient of subgrade reaction is expressed using the three-parameter method. The pile shaft is divided into many small segments and the coefficient of subgrade reaction corresponding to each segment is assumed to be a constant. By making use of the analytical solutions when the coefficient of subgrade reaction is a constant and the continuity of pile responses, the unknown boundary conditions at the pile head are obtained using the iterative method according to the known boundary conditions at the pile head and tip. The semi-analytical solutions of the deflection and inner force of the pile are obtained subsequently.2. The differential equations for the deflection of the pile shafts above and under the ground are deduced respectively, in which the coefficient of subgrade reaction is expressed using the three-parameter method and the P-?effect caused by the vertical load is considered. By making use of the analytical solutions of pile responses under combined vertical and lateral loads when the coefficient of subgrade reaction is a constant and the boundary conditions at the pile head and tip, the power series solutions for the pile shaft above the ground and the semi-analytical solutions for the pile shaft under the ground are obtained.3. The yielding of soil is considered, and then the differential equations for the deflection of laterally loaded pile shafts in the plastic and elastic zones of soil are deduced respectively, in which the coefficient of sugbrade reaction increases linearly with the depth(not equal to zero at the ground surface) and is expressed using the three-parameter method respectively. Together with the boundary conditions at the pile head and tip, solutions of the deflection and inner force of the pile are obtained.4. By assuming the coefficient of subgrade reaction to be a constant, the differential equations for the pile deflection under combined vertical and lateral loads are deduced, in which the yielding of soil is considered and the self-weight of the pile and the friction between the pile and soil are neglected. Thereafter, solutions of the deflection and inner force of the long pile are obtained. By assuming that the coefficient of subgrade reaction is not equal to zero at the ground and increases linearly with the depth, the differential equations for the pile deflection under combined vertical and lateral loads are deduced and the power series solutions of pile responses are obtained subsequently, in which the yielding of soil, the self-weight of the pile and the friction between the pile and soil are considered.5. The soil is assumed to be an ideal, elastic homogeneous, isotropic mass, and the pile is seen as a beam partially embedded in the ground. Solutions of the deflection and inner force of the single pile under combined vertical and lateral loads are obtained by using the finite difference method and integrating the Mindlin displacement solutions.6. Based on the obtained solutions, relevant computer programs are developed by Fortran programming. And then comparisons between the obtained solutions and the pre-existing solutions, the model test results and the field test results are made to show the validity of the obtained solutions.7. Through numerical examples, influences of lateral loads, vertical load, boundary conditions at the pile head and tip, pile stiffness, pile length above ground, parameters in the coefficient of subgrade reaction, yielding displacement of soil, elastic module and Poisson's ratio of the soil on pile responses are analyzed.