Abstract: The buckling stability of extra-long pile which has been increasingly used in high-rise buildings has emerged as a crucial engineering issue. In this research, the formula of critical buckling load of extra-long pile is acquired via energy approach by establishing a model in which the soil resistance is calculated by combining the C method and the constant number method. The self-weight together with side frictional resistance of pile is taking into consideration. Furthermore, the impacts of influential factors on the buckling stability are examined. Results reveal that the influences of unit side friction and self-weight of extra-pile are negligible. The more the number of flexural function items and the smaller the soil resistance, the smaller the buckling critical load is; the larger the pile length and diameter, the larger the buckling critical load is; and the larger the ground soil proportion coefficient, the greater the critical buckling load is. Therefore, in terms of the buckling stability of extra-long pile, large-size extra-long piles have the greatest performance against buckling failure when applied to hard foundations.

Key words: extra-long pile, energy method, critical buckling load, side soil property, pile property