stone column is very inportant site improvement technique

1. GROUND IMPROVEMENT USING
THE
VIBRO-STONE
COLUMN TECHNIQUE
By
SHUVANKAR DAS
M TECH
GEOTECHNICAL ENGINEERING
NIT AGARTALA

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

5. INFLUENCING FACTORS
 Soil
Treatment depth
Area of treatment

6. INSTALLATION TECHNIQUES
NON DISPLACEMENT METHOD
BORED RAMMED SYSTEM
DISPLACEMENT METHOD
VIBRO REPLACEMENT METHOD

7. INSTALLATION PROCEDURE
1. TOP FEED SYSTEM
2. BOTTOM FEED SYSTEM

8. TOP FEED SYSTEM
Penetration Stone Feeding Compaction Finishing

9. TOP FEED SYSTEM

10. BOTTOM FEED SYSTEM
Penetration Stone Feeding Compaction Finishing

11. BOTTOM FEED SYSTEM

12. DESIGN
 DESIGN PARAMETERS
1. Stone Column Diameter
2. Pattern Of Arrangement
D= stone diameter
D

13. 3. Spacing
4. Replacement ratio
K= π for square grids
= 2π/√3 for triangular
column grids
•LOADING PATTERN
•SITE CONDITION
•COLUMN FACTORS
•INSTALATION TECHNIQUE
•SETTLEMENT TOLERANCE

14. 5. Settlement
S= mvσgH

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)

16. 8. Aggregate

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

18. USES

19. LIMITATION
with sensitivity greater than 4
installed at a distance of less than 3.66m

20. CONCLUSION

21. THANK YOU