Calculates skin friction capacity for bored piles in cohesionless soil from effective vertical stress and pile surface area. Unit skin friction = K × σ'v × tan(δ) where K is the earth pressure coefficient and δ is the pile-soil interface friction angle.
Inputs
Pile Diameter Mm
Distance across a circle through its centre. Always confirm units match the rest of the calculation.
Pile Length M
Linear measurement. Ensure consistent units: 1 m = 1,000 mm = 3.281 ft.
Soil Friction Angle Deg
Reference formula or conversion factor shown for context.
Unit Weight Kn M3
Body or object weight. For health calculators, usually in kg or lbs.
K0 Lateral Earth
Force per unit area (Pa). Atmospheric pressure at sea level: 101,325 Pa. Check whether gauge or absolute pressure is required.
Results
skin friction Qf (kN)
Sample size or count used in the calculation.
Ks = K₀(1+sinφ) (stress factor)
Internal force per unit area (Pa or MPa). Must stay below yield strength in service. Beyond yield: permanent deformation. Beyond tensile strength: fracture.
delta = 0.75φ (wall friction)
The change (final minus initial) in the quantity.
mean effective stress at pile mid (kPa)
Internal force per unit area (Pa or MPa). Must stay below yield strength in service. Beyond yield: permanent deformation. Beyond tensile strength: fracture.