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


  1. Swiss Standard SN 670 010b, Characteristic Coefficients of soils, Association of Swiss Road and Traffic Engineers
  2. Das, B., Advanced Soil Mechanics. Taylor & Francis, London & New York, 2008.
  3. Hough, B., Basic soil engineering. Ronald Press Company, New York, 1969.
  4. Terzaghi, K., Peck, R., and Mesri, G., Soil Mechanics in Engineering Practice. Wiley, New York, 1996.
  5. 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).

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