Soil Compaction

# INTRODUCTION
The compact properties of soil is the compaction, if you visualized when any detachable material use to blows then comparessive force increses may result compact. In the engineering we  compact of soil for different purposes :
• To increse the shear strength.
• To increse bearing capacity.
• To decrease the permeability.

#Degree of compactness

Generally, degree of compactness is written in the term of dry density (Yd).
It may be written as,
         Yd = Y/1+w
Where,
   Yd = dry density
  Y = Bulk density
   w = water content

# laboratory compactness test :
• Standard proctor test
• Modified AASTHO test
(It explain in other page )

# Percentage of air void :
The percentage of air void may be defined as the ratio volume of the air in the soil void to the total volume.
    A = Va/ V

From phase diagram :
             Vs + Vw + Vs = V
Dividing both side by V
          Vs/V + Vw/V + Vs/V = 1
       
         Vs/ VGYw  + Ww/YwV = 1-A

      Ws / V×GYw  +   wWs/ YwV = 1-A
  
    Yd / GYw  + wYd / Yw = 1-A
 
    Yd (1/GYw  + w/ Yw) = 1-A
    
    Yd ( 1+w×G/GYw ) = 1-A

       Yd = (1-A)GYw/ (1+WG)

Which is required eqn of dry density in the term of A.

# Zero Air Void Line

The zero air Void line is the condition when all the air is expelled fron the void such that soil is fully saturated.

Note : for the fully saturated A= 0.

# Factor effect the compaction :
• Water content : while the increasing the water content the dry density is decreases.

• Types of soil : dry unit weight achieve also depend upon the types of soil.

• Admixture : lime, Butimin etc are the admixture which also depend on the dry density.

# Effect of compaction :
   .• Soil structure : due to compaction the soil structure may also changed due to the force, here force may be defined as compact load.
 
    • Compressibility : compressibility may also effect. As the compactness increse also compressibility of soil increases.

• Permeability : When the compact is done then the voids on the soil may go to fill up then that cause of decrease of permeability 

# Compaction control :

• Sand replacement method
• Core Cutter method