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External Friction Angle

External Friction

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External Friction Angle

The external friction angle, d, or friction between a soil medium and a material such as the composition from a retaining wall or pile may be expressed in degrees as the following:

### Piles

20 degrees for steel piles (NAVFAC)

0.67f - 0.83f (USACE)

20 degrees for steel (Broms)
f3/4 for concrete (Broms)
f2/3 for timber (Broms)

0.67f (Lindeburg)

Nordlund attempts to more precisely quantify the external friction angle, d, by using various charts based on the angle of internal friction, f, and volume of pile

where f = angle of internal friction of the soil (degrees)

### Retaining Walls

d = 2f         for concrete walls (Coulomb)
3

where f = angle of internal friction of the soil (degrees)

Other soil and soil related properties are listed below:

Angle of Internal Friction
Bearing Capacity Factors
Cohesion
External Friction Angle
Factor of Safety
Lateral Earth Pressure Coefficients
Soil Unit Weights
Young's Modulus or modulus of elasticity

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