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Stone Columns: An Overview
by
S.V. Abhishek & V. Tarachand

Department of Civil Engineering
College of Engineering (A)
And...
 Amongst

Stone Columns

various techniques for improving
in-situ ground conditions, stone columns are
probably the most ...
Applicable Soil Types
Soft,

Non-Compactible, Weak Soils
Granular
Soils with High Fines
Content (in excess of 15%)
Orga...
Functions
 Improve

the bearing capacity of weak soils.

 Carry

high shear stresses by acting as stiff
elements and hen...
Due to high angle of internal friction and stiffness of stone
column when compared to that of in-situ weak soil,
majority ...
Installation Patterns

Area of Influence = (√3/2)S2
De = 1.05S

Area of Influence = S2
De = 1.13S

Time required for conso...
Load Carrying Mechanism
Lateral earth pressure/radial confining
stress against bulging from surrounding
soil.
Surface re...
Estimation of Load Carrying Capacity
 Assumed

that foundation loads are carried only
by the stone columns with no contri...
Settlement Control
 Stone

columns should extend through weak
soil to harder firm strata to control
settlements.
 Provis...
Drainage Function of Stone Columns
 Load

carrying capacity of stone columns is
generated by the top section of the colum...
Failure Mechanism (IS: 15284 Part 1 – 2003)
Installation Techniques
1. Rammed Stone Column Technique
2. Vibro-Replacement

Wet Top-Feed Method
Dry Bottom-Feed Method
Rammed Stone Column by Cased Borehole Method
(Datye and Nagaraju, 1975)
Vibro-Replacement
The Depth Vibrator Principle:
Extension Tube

Coupling
Air or
Water
Supply
Motor
Excentric
Weight
Tip
Depth Vibrator (Courtesy of Keller Group)
Air Chamber and Lock

Extension Tube
Flexible Coupling

Electric Motor
Stone Fee...
Wet Top-Feed Method
(Courtesy of Keller Group)
Dry Bottom-Feed Method with Leader
Supported Rig (Courtesy of Keller Group)
Vibrocat (Courtesy of Keller Group)
Dry Bottom-Feed Crane Hung System
(Courtesy of Keller Group)
Quality Control - Production Monitoring

On-board M4 Computer: Depth, Compaction,
Length of Pull, Re-penetration, Increase...
Stone Column after Installation
Post-Installation Quality Control (Load Test)
Applications in Civil Engineering
 Rail

and Road Embankments
 Bridge Approaches and Abutments
 Offshore Bridge Abutmen...
Ipoh-Rawang Electrified Double Track
(Malaysia)
Ipoh-Rawang Electrified Double Track
(Malaysia)
KVMRT Kajang Maintenance Depot
(Malaysia)
Bridge Approaches and Abutments

Putrajaya, Malaysia
Putrajaya Bridge Approach
Embankment
R.C. Structure
RL +32.0

Top of Bridge Deck
Water Lev. RL +21.5

Embankment
RL +12.0
...
Offshore Bridge Abutments

Johor Bahru, Malaysia
Airport Runways and Taxiways

Alor Setar Airport Project, Malaysia
Storage Tanks

Hazira LNG Terminal, Gujarat
Case History of Highway
Embankment on Stone Column
Treated Ground in Queensland,
Australia (Oh et al. 2007)
Subsoil Properties
520 mm

Untreated

495 mm

SC @ 3m c/c

SC @ 2m c/c
390 mm
Lateral Displacement Profiles
Conclusions
Stone Columns are one of the most versatile
techniques for engineering the ground.
 They can be installed to ...
Acknowledgments

Prof. M.R. Madhav
Professor Emeritus, JNTU
Visiting Professor, IIT Hyderabad

Dr. V.R. Raju
Managing Dire...
Earthquake Rose

Thank

You
Stone columns -  an overview(Ground improvement)
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Stone columns - an overview(Ground improvement)

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Stone columns - an overview(Ground improvement)

  1. 1. Stone Columns: An Overview by S.V. Abhishek & V. Tarachand Department of Civil Engineering College of Engineering (A) Andhra University Visakhapatnam
  2. 2.  Amongst Stone Columns various techniques for improving in-situ ground conditions, stone columns are probably the most versatile, due to their ability to perform a variety of important geotechnical functions.  Origin Germany (1950s)  In India, the use of stone columns began in the early 1970s.  Load bearing columns of well compacted coarse aggregate installed in the ground to serve various purposes such as reinforcement, densification and drainage.
  3. 3. Applicable Soil Types Soft, Non-Compactible, Weak Soils Granular Soils with High Fines Content (in excess of 15%) Organic Soils Marine/Alluvial Clays Liquefiable Soils Waste Fills Reclaimed Fly Ash/Pond Ash Ponds
  4. 4. Functions  Improve the bearing capacity of weak soils.  Carry high shear stresses by acting as stiff elements and hence increase the stability of embankments founded on soft ground.  Facilitate radial drainage (by acting as vertical drains) and dissipate rapidly the excess pore water pressure leading to acceleration of consolidation process and reduced post-construction settlements.  Mitigate the potential for liquefaction and damage by preventing build up of high pore pressure, providing a drainage path and increasing the strength and stiffness of the ground.
  5. 5. Due to high angle of internal friction and stiffness of stone column when compared to that of in-situ weak soil, majority of applied load is transferred to stone column. As a result, less load is transferred to surrounding weak soil which leads to reduction in settlement.
  6. 6. Installation Patterns Area of Influence = (√3/2)S2 De = 1.05S Area of Influence = S2 De = 1.13S Time required for consolidation is directly proportional to square of the drainage path.
  7. 7. Load Carrying Mechanism Lateral earth pressure/radial confining stress against bulging from surrounding soil. Surface resistance or frictional resistance developed between the column material and surrounding weak soil acting upwards within the critical length. Passive resistance mobilized by column material. Load carrying capacity of stone columns = 100 to 400 kN. Note: End bearing is not considered in estimation of load carrying capacity because load carrying mechanism is local perimeter shear.
  8. 8. Estimation of Load Carrying Capacity  Assumed that foundation loads are carried only by the stone columns with no contribution from the intermediate ground. K p (4c + σ 'r )  Hughes & Withers (1974) qa = F.S. where, qa = allowable bearing capacity of stone column Kp = coefficient of passive earth pressure = tan2(45+φ/2) c = cohesion of soil σr’ = average effective radial stress over a depth of ‘4d’ where ‘d’ is the diameter of the column F.S. = factor of safety = 1.5 to 3.0
  9. 9. Settlement Control  Stone columns should extend through weak soil to harder firm strata to control settlements.  Provision of stone columns does not reduce the entire consolidation settlement. The reduction depends on the spacing of stone columns (generally 2.0 to 3.0 m c/c over the site).  Maximum percentage reduction of settlement is 75%.
  10. 10. Drainage Function of Stone Columns  Load carrying capacity of stone columns is generated by the top section of the column which extends to about 4 times the diameter of the stone column.  The length below 4d allows for radial drainage and acceleration of settlements.  To retain continuity of drainage path, it is necessary to provide a 150 mm thick drainage blanket on top of the stone columns.
  11. 11. Failure Mechanism (IS: 15284 Part 1 – 2003)
  12. 12. Installation Techniques 1. Rammed Stone Column Technique 2. Vibro-Replacement Wet Top-Feed Method Dry Bottom-Feed Method
  13. 13. Rammed Stone Column by Cased Borehole Method (Datye and Nagaraju, 1975)
  14. 14. Vibro-Replacement The Depth Vibrator Principle: Extension Tube Coupling Air or Water Supply Motor Excentric Weight Tip
  15. 15. Depth Vibrator (Courtesy of Keller Group) Air Chamber and Lock Extension Tube Flexible Coupling Electric Motor Stone Feeder Pipe Eccentric Weight Top-Feed Vibrator Bottom-Feed Vibrator
  16. 16. Wet Top-Feed Method (Courtesy of Keller Group)
  17. 17. Dry Bottom-Feed Method with Leader Supported Rig (Courtesy of Keller Group)
  18. 18. Vibrocat (Courtesy of Keller Group)
  19. 19. Dry Bottom-Feed Crane Hung System (Courtesy of Keller Group)
  20. 20. Quality Control - Production Monitoring On-board M4 Computer: Depth, Compaction, Length of Pull, Re-penetration, Increase in Power Consumption, Column Diameter
  21. 21. Stone Column after Installation
  22. 22. Post-Installation Quality Control (Load Test)
  23. 23. Applications in Civil Engineering  Rail and Road Embankments  Bridge Approaches and Abutments  Offshore Bridge Abutments  Airport Runways and Taxiways  Storage Tanks (LNG, Crude Oil, LPG etc)  Power Plants
  24. 24. Ipoh-Rawang Electrified Double Track (Malaysia)
  25. 25. Ipoh-Rawang Electrified Double Track (Malaysia)
  26. 26. KVMRT Kajang Maintenance Depot (Malaysia)
  27. 27. Bridge Approaches and Abutments Putrajaya, Malaysia
  28. 28. Putrajaya Bridge Approach Embankment R.C. Structure RL +32.0 Top of Bridge Deck Water Lev. RL +21.5 Embankment RL +12.0 Pile cap Stone columns Bored piles Stone columns
  29. 29. Offshore Bridge Abutments Johor Bahru, Malaysia
  30. 30. Airport Runways and Taxiways Alor Setar Airport Project, Malaysia
  31. 31. Storage Tanks Hazira LNG Terminal, Gujarat
  32. 32. Case History of Highway Embankment on Stone Column Treated Ground in Queensland, Australia (Oh et al. 2007)
  33. 33. Subsoil Properties
  34. 34. 520 mm Untreated 495 mm SC @ 3m c/c SC @ 2m c/c 390 mm
  35. 35. Lateral Displacement Profiles
  36. 36. Conclusions Stone Columns are one of the most versatile techniques for engineering the ground.  They can be installed to improve a variety of ground conditions through several variants of the technique such as rammed stone columns and vibro-replacement (wet top-feed and dry bottomfeed methods).  The in-situ ground is improved by reinforcement, densification and drainage functions performed by the stone columns.  From the case history, the embankment treated with stone columns spaced at 2 m centre to centre experienced the least settlement and lateral displacement when compared to the other cases. 
  37. 37. Acknowledgments Prof. M.R. Madhav Professor Emeritus, JNTU Visiting Professor, IIT Hyderabad Dr. V.R. Raju Managing Director Keller Asia
  38. 38. Earthquake Rose Thank You

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