Stone column

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

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 = 2 π/√ 3 for triangular column grids LOADING PATTERN SITE CONDITION COLUMN FACTORS INSTALATION TECHNIQUE SETTLEMENT TOLERANCE

14. 5. Settlement S= m v σ g H

15. 6. Stress Concentration factor m=σ s / σ g Where, m = Stress concentration factor σ s = Average stress in the stone Column σ g = 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'= T he friction angle of the stone infill σ' ro =the free-field lateral effective stress c u = 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