Geotechdata.info - Updated 18.11.2013
Soil porosity (n) is the ratio of the volume of voids to the total volume of the soil:
n = (V_v) / V
Where V_v is the volume of the voids (empty or filled with fluid), and V is the total volume of the soil.
Porosity is usually used in parallel with soil void ratio (e) , which is defined as the ratio of the volume of voids to the volume of solidsl. The posoity and the void ratio are inter-related as follows:
e = n /(1-n) and n = e / (1+e)
The soil prosoity depends on the consistence and packing of the soil. It is directly affacted by compaction.
Some typical values of soil porosity 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.
|Well graded gravel, sandy gravel, with little or no fines||GW||0.21||0.32||,|
|Poorly graded gravel, sandy gravel, with little or no fines||GP||0.21||0.32||,|
|Silty gravels, silty sandy gravels||GM||0.15||0.22||,|
|Clayey gravels, clayey sandy gravels||GC||0.17||0.27||,|
|Glatial till, very mixed grained||(GC)||-||-||0.20||[4 cited in 5]|
|Well graded sands, gravelly sands, with little or no fines||SW||0.22||0.42||, ,|
|Poorly graded sands, gravelly sands, with little or no fines||SP||0.23||0.43||, ,|
|Silty sands||SM||0.25||0.49||, ,|
|Inorganic silts, silty or clayey fine sands, with slight plasticity||ML||0.21||0.56||,|
|Uniform inorganic silt||(ML)||0.29||0.52||,|
|Inorganic clays, silty clays, sandy clays of low plasticity||CL||0.29||0.41||,|
|Organic silts and organic silty clays of low plasticity||OL||0.42||0.68||, ,|
|Silty or sandy clay||(CL-OL)||0.20||0.64||,|
|Inorganic silts of high plasticity||MH||0.53||0.68||,|
|Inorganic clays of high plasticity||CH||0.39||0.59||,|
|Soft glacial clay||-||-||-||0.55||[4 cited in 5]|
|Stiff glacial clay||-||-||-||0.38||[4 cited in 5]|
|Organic clays of high plasticity||OH||0.50||0.75||, ,|
|Soft slightly organic clay||(OH-OL)||-||-||0.66|| cited in |
|Peat and other highly organic soils||Pt||-||-||[4 cited in 5]|
|soft very organic clay||(Pt)||-||-||0.75|| cited in |
Geotechdata.info, Soil void ratio, http://geotechdata.info/parameter/soil-void-ratio.html (as of November 16, 2013).
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