Analytical Formula of Pile and Stress Influence Coefficient for File Foundation Standard

In the Technical Code for Building Pile Foundations (JGJ 94—2008), the uniform distribution and the triangular distribution of pile side stress against depth were considered, and the uniform distribution of pile end stress affected by pile diameter was also taken into account. Meanwhile, the Geddes analytical formula was used in the pile side stress influence coefficient, and the formula (33) in the paper "Calculation Formula of Vertical Stress in Foundation Based on Mindlin Formula" published by Xu Zhiying in the fourth issue of Civil Engineering Journal in 1957 was used in the pile end stress influence coefficient. However, the square root property of √(z-L)²=|z-L|≠z-L was neglected in Xu’s formula (33), so this formula was only applicable to the case under the pile end (z>L). Therefore, the uniformly distributed stress at pile end affected by pile diameter was considered on the basis of the Mindlin stress solution of buried depth concentration force, and then the one-dimensional integral analytic general solution of pile end stress influence coefficient on pile axis was derived again. The solution function is discontinuous to variable z at the pile end (z=L), and the discontinuity point is a jump discontinuity point. Moreover, the calculation results of the general solution were compared and verified by the one-dimensional and two-dimensional numerical integral values, as well as the Standard’s tabulated values.