<span ">Soil friction angle is a shear strength parameter of soils. Its definition is derived from the Mohr-Coulomb failure criterion and it is used to describe the friction shear resistance of soils together with the normal effective stress.Soil friction angle is a shear strength parameter of soils. Its definition is derived from the Mohr-Coulomb failure criterion and it is used to describe the friction shear resistance of soils together with the normal effective stress.
In the stress plane of Shear stress-effective normal stress, the soil friction angle is the angle of inclination with respect to the horizontal axis of the Mohr-Coulomb shear resistance line.
Typical values of soil friction angle
Some typical values of soil friction angle are given below for different USCS soil types at normally consolidated condition unless otherwise stated. These values should be used only as guidline for geotechnical problems; however, specific conition of each engineering problem often needs to be considered for an appropriate choice of geotechnical parameters.
| Description | USCS | Soil friction angle [°] | Reference | ||
| min | max | Specific value | |||
| Well graded gravel, sandy gravel, with little or no fines | GW | 33 | 40 | [1],[2], | |
| Poorly graded gravel, sandy gravel, with little or no fines | GP | 32 | 44 | [1], | |
| Sandy gravels - Loose | (GW, GP) | 35 | [3 cited in 6] | ||
| Sandy gravels - Dense | (GW, GP) | 50 | [3 cited in 6] | ||
| Silty gravels, silty sandy gravels | GM | 30 | 40 | [1], | |
| Clayey gravels, clayey sandy gravels | GC | 28 | 35 | [1], | |
| Well graded sands, gravelly sands, with little or no fines | SW | 33 | 43 | [1], | |
| Well-graded clean sand, gravelly sands - Compacted | SW | - | - | 38 | [3 cited in 6] |
| Well-graded sand, angular grains - Loose | (SW) | 33 | [3 cited in 6] | ||
| Well-graded sand, angular grains - Dense | (SW) | 45 | [3 cited in 6] | ||
| Poorly graded sands, gravelly sands, with little or no fines | SP | 30 | 39 | [1], [2], | |
| Poorly-garded clean sand - Compacted | SP | - | - | 37 | [3 cited in 6] |
| Uniform sand, round grains - Loose | (SP) | 27 | [3 cited in 6] | ||
| Uniform sand, round grains - Dense | (SP) | 34 | [3 cited in 6] | ||
| Sand | SW, SP | 37 | 38 | [7], | |
| Loose sand | (SW, SP) | 29 | 30 | [5 cited in 6] | |
| Medium sand | (SW, SP) | 30 | 36 | [5 cited in 6] | |
| Dense sand | (SW, SP) | 36 | 41 | [5 cited in 6] | |
| Silty sands | SM | 32 | 35 | [1], | |
| Silty clays, sand-silt mix - Compacted | SM | - | - | 34 | [3 cited in 6] |
| Silty sand - Loose | SM | 27 | 33 | [3 cited in 6] | |
| Silty sand - Dense | SM | 30 | 34 | [3 cited in 6] | |
| Clayey sands | SC | 30 | 40 | [1], | |
| Calyey sands, sandy-clay mix - compacted | SC | 31 | [3 cited in 6] | ||
| Loamy sand, sandy clay Loam | SM, SC | 31 | 34 | [7], | |
| Inorganic silts, silty or clayey fine sands, with slight plasticity | ML | 27 | 41 | [1], | |
| Inorganic silt - Loose | ML | 27 | 30 | [3 cited in 6] | |
| Inorganic silt - Dense | ML | 30 | 35 | [3 cited in 6] | |
| Inorganic clays, silty clays, sandy clays of low plasticity | CL | 27 | 35 | [1], | |
| Clays of low plasticity - compacted | CL | 28 | [3 cited in 6] | ||
| Organic silts and organic silty clays of low plasticity | OL | 22 | 32 | [1], | |
| Inorganic silts of high plasticity | MH | 23 | 33 | [1], | |
| Clayey silts - compacted | MH | 25 | [3 cited in 6] | ||
| Silts and clayey silts - compacted | ML | 32 | [3 cited in 6] | ||
| Inorganic clays of high plasticity | CH | 17 | 31 | [1], | |
| Clays of high plasticity - compacted | CH | 19 | [3 cited in 6] | ||
| Organic clays of high plasticity | OH | 17 | 35 | [1], | |
| Loam | ML, OL, MH, OH | 28 | 32 | [7], | |
| Silt Loam | ML, OL, MH, OH | 25 | 32 | [7], | |
| Clay Loam, Silty Clay Loam | ML, OL, CL, MH, OH, CH | 18 | 32 | [7], | |
| Silty clay | OL, CL, OH, CH | 18 | 32 | [7], | |
| Clay | CL, CH, OH, OL | 18 | 28 | [7], | |
| Peat and other highly organic soils | Pt | 0 | 10 | [2], | |
Correlation between SPT-N value, friction angle, and relative density
| SPT N3 [Blows/0.3 m - 1 ft] |
Soi packing
|
Relative Density [%]
|
Friction angle
[°] |
|---|---|---|---|
|
< 4
|
Very loose
|
< 20
|
< 30
|
|
4 -10
|
Loose
|
20 - 40
|
30 - 35
|
|
10 - 30
|
Compact
|
40 - 60
|
35 - 40
|
|
30 - 50
|
Dense
|
60 - 80
|
40 - 45
|
|
> 50
|
Very Dense
|
> 80
|
> 45
|
Refrences
- Swiss Standard SN 670 010b, Characteristic Coefficients of soils, Association of Swiss Road and Traffic Engineers Swiss Standard SN 670 010b, Characteristic Coefficients of soils, Association of Swiss Road and Traffic Engineers
- JON W. KOLOSKI, SIGMUND D. SCHWARZ, and DONALD W. TUBBS, Geotechnical Properties of Geologic Materials, Engineering Geology in Washington, Volume 1, Washington Division of Geology and Earth Resources Bulletin 78, 1989, Link
- Carter, M. and Bentley, S. (1991). Correlations of soil properties. Penetech Press Publishers, London.
- Meyerhof, G. (1956). Penetration tests and bearing capacity of cohesionless soils. J Soils Mechanics and Foundation Division ASCE, 82(SM1).
- Peck, R., Hanson,W., and Thornburn, T. (1974). Foundation Engineering Handbook. Wiley, London.
- Obrzud R. & Truty, A.THE HARDENING SOIL MODEL - A PRACTICAL GUIDEBOOK Z Soil.PC 100701 report, revised 31.01.2012
- Minnesota Department of Transportation, Pavement Design, 2007