Soil Water & Types of Soil Water | Properties of Soil | Soil Mechanics

  Soil water & Types of soil  

Water present in the soil in any form is termed soil water. Many types of sοil water.

• Ground / Free / Gravity water
• Capillary water
• Structural water
• Adsorbed water

Ground / Free / Gravity water:

• It is subsurface water that fills the voids continuously up to groundwater table level ( So is called ground water ) .
• This water is subjected to no force ( So is called free water ) other than its own weight ( So is called gravity water )  .
• It obeys all the laws of hydraulics and is capable of moving under hydrodynamic force.

Capillary water:

• It’s the water which is lifted above ground water table level by capillary force.
• It remained in suspension in the voids of soil.
• It also obeys laws of hydraulic and  moves under hydrodynamic force.

Note: Groundwater and capillary water are also terms as pore water.

Structural water

• It is the water which is chemically combined with crystal structure of the soil.
• Under loading conditions observed in engineering, structural water cannot be removed  even by increased temperature at 105 to 110 degree.

Adsorbed water / Pellicular water 

1. Hygroscopic water
2. Film water

Hygroscopic water

• It is the water which is adsorbed by soil solids  from the atmosphere by physical force of attraction and is held over its surface due to adhesion.
• The extent of water adsorbed by the soil solid ∝ ( 1/size .d) ∝ surface area.
• Hygroscopic water is not affected by Gravity or capillary forces.
• It has higher density, viscosity & boiling point and lesser freezing point than groundwater.
• The hygroscopic adsorption capacity of different soil.

1. The water adsorption capacity for clay⇒  16 – 17 %.
2. The water adsorption capacity for silt⇒  6 – 7 %.
3. The water adsorption capacity for Sand⇒  1-2 %.

Film water

• It is the water that is present as a film over the layer of hygroscopic water.
• It is formed due to the condensation of aqueous vapor.
• It is also held by soil solids but has lesser adhesion than hygroscopic water.

Hygroscopic water & Film water not followed the law of Hydrodynamics.

Soil Water & Types of Soil Water

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