Design situation

Geometry
Pile length

Outside pile diameter

Wall thickness

Gross cross-sectional area of pile base

Nett (i.e. annular) cross-sectional area of pile base

Material properties
Unit weight of soil below water table

Undrained shear strength of soil

Effective unit weight of soil

Unit weight of water

Calculation of bearing capacity

Shaft resistance
(Values in right-hand column apply at reference depth)

Vertical effective stress in free-field at any depth z is:

Normalised undrained strength at depth z is:

Shaft adhesion factor at depth z is:

Ref: API RP 2A-WSD (2002), §6.4.2 (6.4.2-2)

Skin friction at depth z is:

Ref: API RP 2A-WSD (2002), §6.4.2 (6.4.2-1)

Total shaft resistance is then:

Base resistance
Ultimate bearing pressure

Ref: API RP 2A-WSD (2002), §6.4.2 (6.4.2-3)
Total base resistance (assuming pile is plugged) is then:

Total resistance

Revision history
1.00 27/01/2005 AJB created