General Approach

Let’s start with simple clarifications for the sake of establishing a common understanding of the terms which are going to be used frequently throughout this manual.

Ultimate and allowable compressive load bearing capacities of bored piles (drilled shafts) with elements for skin friction and tip resistance, are defined below:

$$Q_u = Q_s + Q_b - W$$

$$Q_a = \frac{q_s \cdot A_s}{{FS}_s} + \frac{q_b \cdot A_b}{{FS}_b} - W$$

Please note that limiting values for ultimate skin friction and tip resistance, which will be given in the following chapters, are derived from Budhu (2011), pp. 544-545 except where noted.