Symbol Description
\(A_b\) area of pile base
\(A_s\) area of shaft surface
\(c_u\) undrained cohesion at the pile toe
\(c_{u\text{, avg}}\) average undrained cohesion of soil layer
\({FS}_b\) factor of safety for tip resistance
\({FS}_s\) factor of safety for skin friction
\(h_\text{penet.}\) depth of penetration into the layer
\(K\) coefficient of lateral earth pressure
\(N_c\) bearing capacity factor
\(N_q\) bearing capacity factor (function of shear resistance angle, see Table 1)
\(N_\text{SPT}\) standard penetration test blow count
\(p_a\) atmospheric pressure (101 kPa or 14.7 psi)
\(Q_a\) allowable bearing capacity
\(Q_b\) ultimate tip resistance
\(q_b\) ultimate unit tip resistance
\(Q_s\) ultimate skin friction
\(q_s\) ultimate unit skin friction
\(Q_u\) ultimate bearing capacity
\(W\) submerged pile weight
\(\alpha\) factor of adhesion (see Figure 1 for weak rock and IGMs)
\(\phi’\) effective angle of internal friction for the soil layer
\(\phi_\text{red} \) coefficient of diameter reduction for weak rock and IGMs
\(\sigma_c\) unconfined compressive strength of the weak rock or IGM
\(\sigma_v’\) vertical effective stress at the pile toe
\(\sigma_{v \text{, avg}}’\) average vertical effective stress along the layer