Abstract
This paper attempts to propose the formulas for estimating vertical spring constants of the pile top under a condition named the elastic limit state as well as to grasp quantitatively this limit state against the vertical force of a single pile.
On the basis of a new definition of the ultimate bearing capacity through the settlement level (settlement of the pile top/diameter of pile), we present an equation for predicting the ultimate bearing capacity which is applicable irrespectively of the supporting system of piles.
Then, evaluation of safety factors for the ultimate limit state is made by considering accuracy in this equation.
