Test of Specific Gravity | Properties of Soil | Soil Mechanics

  Test of Specific Gravity  

  • The specific gravity of soil can be computed using a 50 ml density bottle, 500 ml flask, or by pycnometer.
  • The density bottle method is the most accurate among all & is suitable for all types of soil.
  • Flask & Pycnometer is suitable to be used for coarse-grained soil &  If it is used for fine-grained soil then kerosene is used in the test instead of water  (  as kerosene is a better wetting reagent than water)
  • In the density bottle, only kerosene is used.
  • Steps of observation in all same.

Density bottle⇒all types of soil ⇒ only kerosene used.

Flask & Pycnometer 

  • Coarse-Grained soil ⇒ Water /Kerosene.
  • Fine-Grained soil ⇒Only Kerosene Used.

The process of determining specific gravity are same for a 50 ml density bottle, 500 ml flask, or Pycnometer. Here we use a pycnometer.

Specific Gravity Test
Specific Gravity Test

W1=Weight of the empty pycnometer.

W2= Weight of pycnometer + Dry soil.

W3= Weight of pycnometer + Dry soil + water.

W4= Weight of pycnometer + water.


\(\mathrm{G} / \mathrm{GS}=\frac{\text { Weight of solid of given soil }}{\text { weight of standard fluid of same volume }}\)

Standard Fluid=Water

\(G=\frac{Ws}{Ww orWk}\) \(G=\frac{ρ_s}{ρ_w  or ρ_k}\) \(G=\frac{Ms}{Mw  or Mk}\)

Mass of solids Ms = M1-M2 =Mass of dry soil =Md

Mass of water in stage 3 = M3-M2

Mass of water in stage 4 = M4-M1

(Mass of water having volume same as that of solids= Mass of water in stage 4 -Mass of water in stage in stage 3)

Mass of water having volume same as that of solids= (M4-M1)-(M3-M2)



Or M4+M3-Md+Mw(whose volume is the same as that of solids )



\(G=\frac{Md}{M4-M3+Md}\)  ***

G = Specific Gravity of solid.

Note: Kerosene is used instead of water for fine-grained soil. Then Specific Gravity is calculated as

\(G=\frac{M2-M1}{M4-M3+M2-M1}×Gk\)  ***

Gk = Specific Gravity of Kerosene.

SubjectSoil Mechanics
UnitSoil Formation & Properties of Soil
TopicTest of Specific Gravity
Next TopicTest of Unit Weight of Soil
Previous TopicInterrelationship Between the Properties of Soil


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