In comparing the second and third term in Eq. 6.14, the value of B (width of pile) is much less
than the embedment depth Df of the pile. Therefore, the first term in Eq. 6.14 can be neglected.
The value of gt Df in the second term in Eq. 6.14 is equivalent to the total vertical stress sv at the
pile tip. For cohesionless soil and using an effective stress analysis, the groundwater table must be
included and hence the vertical effective stress s′ v can be substituted for sv. Equation 6.14 reduces to