Vibro replacement stone columns are a ground improvement technique to improve the load bearing capacity and reduce the settlement of the soil. On many occasions, it is noted that the local soil is, by nature, unable to bear the proposed structure, so the use of ground improvement techniques may be necessary. Use of stone columns is one such technique. The stone column consists of crushed coarse aggregates of various sizes. The ratio in which the stones of different sizes will be mixed is decided by design criteria
2. WHAT IS THE REQUIREMENT OF
GROUND IMPROVEMENT?
To alter the natural properties of rock or soil
Reducing compressibility and permeability
Increasing strength ,bearing capacity
3. WHY STONE COLUMNS?
Offer alternative foundation system to the conventional pile
foundation system
4. WHAT IS STONE COLUMN?
A ground improvement technique
to improve the load bearing capacity
and reduce the settlement of the soil
Stone column consists of crushed
coarse aggregates of various sizes
15. 6. Stress Concentration factor
m=σs/ σg
Where,
m = Stress concentration factor
σs = Average stress in the stone
Column
σg = The stress in the soil within
the unit cell
The value of m generally lies between 2.5 and 5 at the ground surface
7. Bearing Capacity q = ultimate vertical stress
φ'= The friction angle of the stone
infill
σ'ro =the free-field lateral effective
stress
cu = is the undrained shear
strength
Hughes and Witches(1974)
17. FUNCTIONS AND USES
1. To increase the bearing capacity
2. Improves the stiffness of subsoil to decrease settlements
3. To carry very high loads
4. More economical than piling
5. No waiting period after installation
6. homogenizes variable soil properties