Degree of Saturation, Air Content and Percentage Air Voids | Properties of Soil | Soil Mechanics

  Degree of Saturation  

It is defined as the ratio of the volume of water (Vw) to the volume of voids (Vv) present in a given soil mass. It is represented as ‘s’.

Phase Diagram,   Degree of Saturation  
Phase Diagram.

s = (Vw / Vv)*100.

Degree of Saturation is the Unit less.

0% ≤ s ≤ 100%.

Type of Soil According to Degree of Saturation

Depending upon the degree of saturation in a given soil mass it can be classified as:

Type of soilDegree of Saturation
dry soil ( s≤0)
humid soil(0<s<.25)
damp soil(.25<s<.5)
moist soil(.5<s<.75)
wet soil(.75<s<1)
saturated soil(s≥1)
Type of soil according to degree of saturation, Degree of Saturation, Air Content and Percentage Air Voids
Type of soil according to saturation

  Air Content (ac)  

It is defined as the ratio of the volume of air (Va) to the volume of voids (Vv) present in a given soil mass. It is represented as ‘ac’.

ac = (Va / Vv)*100.

Air Content (ac) is the Unit less.

0% ≤ ac ≤ 100%.

⇒Vv = Va + Vw.  (Divide by Vv on both side).

⇒Vv/Vv = Va/Vv +Vw/Vv.

⇒ac+ s =1.


  Percentage Air Voids (ηa)  

It is defined as the ratio of the volume of air (Va) to the volume of soil mass (V) present in a given soil mass. It is represented as ‘ηa’.

ηa= (Va / V)*100

Percentage Air Voids is the Unit less.

0% ≤ ηa < 100%.

ηa= Va/V.

ηa= (Va*Vv) / (V*Vv).  ( Multiply Numerator & Denominator by Vv.)

ηa= (Va/Vv) * (Vv/V).

ηa= ac×η.


SubjectSoil Mechanics
UnitSoil Formation & Properties of Soil
TopicDegree of Saturation, Air Content, Percentage Air Voids
Next TopicUnit Weight and Density
Previous TopicVoid Ratio and Porosity of Soil

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