Friction Angle

About Friction Angle

Friction angle together with cohesion define the shear strength parameters of soil. For granular / cohesionless soil (c = 0) friction angle is mainly estimated either from laboratory tests or from correlations with N SPT number.
There are many correlations to estimate friction angle for granular material from N SPT values. They are based on the uncorrected N SPT (field measurements) or based on the corrected (N1)60 value.

  Method 2: CIRIA 143 (1995)

Method 1 : Peck, Hanson and Thornburn (1974)

\(ϕ′=27.1+0.3N′+0.00054N^{r2}\)

Note: Above an N SPT of 60 values are reduced to a more conservative estimate of
friction angles.

Method 2 : Defines friction angle from CIRIA Report 143 (1995) after Peck, Hanson and Thornburn.

Method 3 : Defines friction angle as per Terzaghi, Peck & Mersi (1996). Three curves are presented for fine, coarse
and average soil particles.

Method 4 : Defines friction angle as per Meyerhof (1986).

Method 5 : Defines friction angle as per Dunham (1954).

\( ϕ′=\sqrt{12N}+20\)

Method 6 : Defines friction angle as per Osaki et al. (1959)

Method 3: Terzaghi, Peck & Mersi (1996)

\(ϕ′=(20⋅N)^{0.5}+15\)

Typical friction angle values and density versus N SPT number are presented in a tabulated format at table below:

N value
(blows/ft or 305 mm)		 Relative
Density		 Approximate \(ϕ′_{tc}\)(degrees)
Method 1 Method 4
0 to 4 very loose < 28 < 30
4 to 10 loose 28 to 30 30 to 35
10 to 30 medium 30 to 36 35 to 40
30 to 50 dense 36 to 41 40 to 45
> 50 very dense > 41 > 45
   

References

  1. Terzaghi, K. and Peck, R.B. (1967) Soil Mechanics in Engineering Practice. John Wiley & Sons, New York.
  2. Peck, R.B., Hanson, W.E., and Thornburn, T.H., (1974), “Foundation Engineering”, John Wiley & Sons, 514p.
  3. Meyerhof, G.G., (1956), “Penetration Tests and Bearing Capacity of Cohesionless Soils”, Jnl. Soil Mech. & Found. Div., ASCE, Vol. 82, No. SM1.
  4. EPRI EL-6800, Project 1493-6, Final Report, Aug 1990, Manual on Estimating Soil Properties for Foundation Design.
  5. CIRIA Report 143, 1995, The Standard Penetration Test (SPT): Methods and Use.
Activated ags files
# Project Ags Name Method Actions
SN Method NSPT Value Friction Angleo
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