Soil void ratio (e) is the ratio of the volume of voids to the volume of solids:
e = (V_v) / (V_s)
Where V_v is the volume of the voids (empty or filled with fluid), and V_s is the volume of solids.
Void ratio is usually used in parallel with soil porosity (n) , which is defined as the ratio of the volume of voids to the total volume of the soil. The posoity and the void ratio are inter-related as follows:
e = n /(1-n) and n = e / (1+e)
The value of void ratio depends on the consistence and packing of the soil. It is directly affacted by compaction. Some typical values of void ratio for different soils are given below only as general guidelines.
Typical values of soil void ratio for different soils
Some typical values of void ratio 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 | Void ratio [-] | Reference | ||
| min | max | Specific value | |||
| Well graded gravel, sandy gravel, with little or no fines | GW | 0.26 | 0.46 | [1], | |
| Poorly graded gravel, sandy gravel, with little or no fines | GP | 0.26 | 0.46 | [1], | |
| Silty gravels, silty sandy gravels | GM | 0.18 | 0.28 | [1], | |
| Gravel | (GW-GP) | 0.30 | 0.60 | [2], | |
| Clayey gravels, clayey sandy gravels | GC | 0.21 | 0.37 | [1], | |
| Glatial till, very mixed grained | (GC) | - | - | 0.25 | [4 cited in 5] |
| Well graded sands, gravelly sands, with little or no fines | SW | 0.29 | 0.74 | [1], [2], | |
| Coarse sand | (SW) | 0.35 | 0.75 | [2], | |
| Fine sand | (SW) | 0.40 | 0.85 | [2], | |
| Poorly graded sands, gravelly sands, with little or no fines | SP | 0.30 | 0.75 | [1], [2], | |
| Silty sands | SM | 0.33 | 0.98 | [1], [2], | |
| Clayey sands | SC | 0.17 | 0.59 | [1], | |
| Inorganic silts, silty or clayey fine sands, with slight plasticity | ML | 0.26 | 1.28 | [1], | |
| Uniform inorganic silt | (ML) | 0.40 | 1.10 | [3], | |
| Inorganic clays, silty clays, sandy clays of low plasticity | CL | 0.41 | 0.69 | [1], | |
| Organic silts and organic silty clays of low plasticity | OL | 0.74 | 2.26 | [1], [3], | |
| Silty or sandy clay | (CL-OL) | 0.25 | 1.80 | [3], | |
| Inorganic silts of high plasticity | MH | 1.14 | 2.10 | [1], | |
| Inorganic clays of high plasticity | CH | 0.63 | 1.45 | [1], | |
| Soft glacial clay | - | - | - | 1.20 | [4 cited in 5] |
| Stiff glacial clay | - | - | - | 0.60 | [4 cited in 5] |
| Organic clays of high plasticity | OH | 1.06 | 3.34 | [1], [3], | |
| Soft slightly organic clay | (OH-OL) | - | - | 1.90 | [4] cited in [5] |
| Peat and other highly organic soils | Pt | - | - | [4 cited in 5] | |
| soft very organic clay | (Pt) | - | - | 3.00 | [4] cited in [5] |
REFERENCES
- Swiss Standard SN 670 010b, Characteristic Coefficients of soils, Association of Swiss Road and Traffic Engineers
- Das, B., Advanced Soil Mechanics. Taylor & Francis, London & New York, 2008.
- Hough, B., Basic soil engineering. Ronald Press Company, New York, 1969.
- Terzaghi, K., Peck, R., and Mesri, G., Soil Mechanics in Engineering Practice. Wiley, New York, 1996.
- Obrzud R. & Truty, A.THE HARDENING SOIL MODEL - A PRACTICAL GUIDEBOOK Z Soil.PC 100701 report, revised 31.01.2012
Citation :
Geotechdata.info, Soil void ratio, http://geotechdata.info/parameter/soil-void-ratio.html (as of November 16, 2013).