Abstract: In order to reduce the influences of side friction resistance for pile body during the determination process of equilibrium point of self-balanced method, the finite element simulation was used, the finite element model of pile-soil was established and the equilibrium point positions of pile under the different conditions of foundation bearing capacity, pile lengths and pile diameters were analyzed. When the bearing capacity of loess is 120 kPa, the pile length is 75m and the pile diameter is 800mm, the 1/3, 1/7, 7/25, 21/100 and 17/100 points of pile body are selected as the calculation nodes of equilibrium point according to the site test results and the principle of bisection method. The displacements of the upper and lower piles are 4 mm and 4.1 mm respectively when the 17/100 point of pile body is selected as the calculation node of equilibrium point, and the result is reasonable. According to the established finite element model, the equilibrium points were obtained under the different working conditions such as when the foundation bearing capacity increases from 110 to 250 kPa, the pile length increases from 30 to 110 m, and the pile diameter increases from 600 to 1 500 mm, a series of equilibrium diagrams were drawn. Equilibrium diagrams can provide a reference for the determination equilibrium point in the self-balancing method.

Key words: pile foundation, finite element simulation, self-balancing test, extremely long piles, equilibrium point