Unit Weight of Soil
About Unit Weight of Soil tool
The unit weight of soil, also known as bulk density, is defined as the weight per unit volume of soil. It represents the average weight of soil particles, including solids and voids, within a given volume. The unit weight of soil is expressed in terms of mass per unit volume, typically in metric units such as kilograms per cubic meter (kg/m3) or force per cubic meter (kN/m3). The unit weight of soil can vary depending on several factors, including the type of soil, its gradation, moisture content, compaction, and the presence of organic matter or other constituents.
This tool estimates the unit weight of soil from N SPT number. Typical ranges of unit weight values per soil type are reported below.
Table 1: Typical values of unit weight of soil from Bowels, Foundation Analysis, 1997.
| N SPT | Unit Weight, γtotal lb/ft3 |
Unit Weight, γtotal kN/m3 |
|---|---|---|
| 0 to 4 | 70 to 100 | 11.0 to 15.7 |
| 4 to 10 | 90 to 115 | 14.1 to 18.1 |
| 10 to 30 | 110 to 130 | 17.3 to 20.4 |
| 30 to 50 | 110 to 140 | 17.3 to 22.0 |
| > 50 | 130 to 150 | 20.4 to 23.6 |
Table 2: Typical values of unit weight of soil from Lindeburg, Civil Engineering Reference Manual for the PE Exam, 8th Edition.
| Soil Type | Unit Weight, γtotal lb/ft3 |
Unit Weight, γtotal kN/m3 |
|---|---|---|
| Loose, uniform Sand | 90 to 118 | 14.1 to 18.5 |
| Dense, uniform Sand | 109 to 130 | 17.1 to 20.4 |
| Loose, well graded Sand | 99 to 124 | 15.6 to 19.5 |
| Dense, well graded sand | 116 to 135 | 18.2 to 21.2 |
| Soft Clay | 130 to 110 | 20.4 to 17.3 |
| Stiff Clay | 106 to 125 | 16.7 to 19.6 |
Table 3: Typical values of unit weight of soil from Soil Mechanics Design Manual, NAVFA 7.01, 1986.
| Soil Type | Unit Weight, γtotal lb/ft3 |
Unit Weight, γtotal kN/m3 |
|---|---|---|
| Uniform, fine to medium Sand | 84 to 136 | 13.2 to 21.4 |
| Uniform Silt | 81 to 136 | 12.7 to 21.4 |
| Silty Sand | 88 to 142 | 13.8 to 22.3 |
| Well-graded Sand | 86 to 148 | 13.5 to 23.2 |
| Silty Sand and Gravel | 90 to 155 | 14.1 to 24.3 |
| Sandy or Silty Clay | 100 to 147 | 15.7 to 23.1 |
| Uniform Silty Clay with Gravel | 115 to 151 | 18.1 to 23.7 |
| Well graded Gravel, Sand, Silt and Clay | 125 to 156 | 19.6 to 24.5 |
| Clay | 94 to 133 | 14.8 to 20.9 |
| Organic Silt | 87 to 131 | 13.7 to 20.6 |
| Organic Clay | 81 to 125 | 12.7 to 19.6 |
References
- P. Anbazhagan et al., 2016, Correlation of densities with shear wave velocities and SPT N values.
- Hoek, E. and Bray, J.W. 1981. Rock Slope Engineering. 3rd Ed. The Institution of Mining and Metallurgy, London.
- Joseph E. Bowles, P.E., S.E., 1997, Foundation Analysis and Design, Fifth Edition.
Activated ags files
| # | Project | Ags Name | Method | Actions |
|---|
| SN | Description/ Soil Type | N SPT Value (N) | Unit weight of soil or bulk density (kN/m3) |
|---|