Abstract: When the top of a pile in soft ground is subjected to a large horizontal load, the traditional m method would underestimate the bending moment and deformation of the pile element. Therefore, it is necessary to propose relevant calculation methods for this problem. Simplifying the soft ground to an ideal elastoplastic body, and assume that there exists a critical point at a certain depth of the ground where the soil mass above the critical point behaves plastically and the soil mass below the point behaves elastically. The deflection differential control equation of the pile is established and a simplified elastoplastic calculation method for the horizontally loaded single pile is proposed. The results of field measurements and parametric study show that the maximum bending moment calculated by the simplified elastoplastic calculation method is 38.1% more accurate to field measurement in comparison with the traditional m method, and the calculation accuracy of the maximum horizontal displacement of the pile is improved by 22.3%. It indicates that the boundary conditions at pile top have significant impact on the distribution of lateral deflection and bending moment along the pile. Moreover, parameters of soil limit resistance and soil shape have remarkable influence on the maximum bending moment and lateral deflection and it is recommended to choose the lower values in pile design.

Key words: pile foundations, laterally loaded pile, large displacement, simplified elastoplastic calculation method, m-method