Stone columns Anoverview 140117085610 Phpapp01

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Stone Columns: An Overview

byS.V. Abhishek & V. Tarachand

Department o Civil !n"ineerin"Colle"e o !n"ineerin" #A$Andhra %niversity

Visakhapatnam


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p

Stone ColumnsAmongst various techniques for improving in-

situ ground conditions, stone columns are probablythe most versatile, due to their ability to perform avariety of important geotechnical functions.

Origin Germany (19!s" #n #ndia, the use of stone columns began in the

early 19$!s.%oad bearing columns of &ell compacted coarse

aggregate installed in the ground to serve variouspurposes such as reinforcement, densification anddrainage.


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unctions #mprove the bearing capacity of &ea+ soils.

)arry high shear stresses by acting as stiffelements and hence increase the stability ofemban+ments founded on soft ground.

acilitate radial drainage (by acting as verticaldrains" and dissipate rapidly the ecess pore &aterpressure leading to acceleration of consolidationprocess and reduced post-construction settlements.0itigate the potential for liquefaction and damageby preventing build up of high pore pressure,providing a drainage path and increasing thestrength and stiffness of the ground.


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4ue to high angle of internal friction and stiffness of stonecolumn &hen compared to that of in-situ &ea+ soil,ma5ority of applied load is transferred to stone column.

As a result, less load is transferred to surrounding &ea+soil &hich leads to reduction in settlement.


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'nstallation (atterns

Area of #nfluence 6 (78"' Area of #nfluence 6 '

4e6 1.!' 4e6 1.18'

:ime required for consolidation is directly proportionalto square of the drainage path.


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)oad Carryin" *echanism%ateral earth pressureradial confiningstress against bulging from surrounding

soil.'urface resistance or frictionalresistance developed bet&een thecolumn material and surrounding &ea+

soil acting up&ards &ithin the criticallength.

3assive resistance mobili;ed bycolumn material.

%oad carrying capacity of stonecolumns 6 1!! to

ote= >nd bearing is not considered inestimation of load carrying capacity

because load carrying mechanism islocal perimeter shear.


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!stimation o )oad Carryin" CapacityAssumed that foundation loads are carried onlyby the stone columns &ith no contribution fromthe intermediate ground.

ughes ? *ithers (19$


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Settlement Control'tone columns should etend through &ea+

soil to harder firm strata to controlsettlements.

3rovision of stone columns does not reducethe entire consolidation settlement. :hereduction depends on the spacing of stonecolumns (generally .! to 8.! m cc over thesite".

0aimum percentage reduction of settlementis $/.


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Draina"e unction o Stone Columns

%oad carrying capacity of stone columns is

generated by the top section of the column&hich etends to about < times the diameterof the stone column.

:he length belo&


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ailure *echanism #'S: +,-/ (art + 0 -112$


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'nstallation Techni3ues

1. 2ammed 'tone )olumn :echnique

. ibro-2eplacement

*et :op-eed 0ethod

4ry Hottom-eed 0ethod


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4ammed Stone Column by Cased 5orehole *ethod

#Datye and 6a"ara7u8 +9,$


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Vibro;4eplacement

Extension Tube

Coupling

Air or

Water

Supply

Motor

Excentric

Weight

Tip

:he 4epth ibrator 3rinciple=


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Depth Vibrator #Courtesy o


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>et Top;eed *ethod

#Courtesy o


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Dry 5ottom;eed *ethod with )eader

Supported 4i" #Courtesy o


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Vibrocat #Courtesy o


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Dry 5ottom;eed Crane ?un" System

#Courtesy o


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@uality Control ; (roduction *onitorin"

On-board 0< )omputer= 4epth, )ompaction,%ength of 3ull, 2e-penetration, #ncrease in 3o&er

)onsumption, )olumn 4iameter


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Stone Column ater 'nstallation


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(ost;'nstallation @uality Control #)oad Test$


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Applications in Civil !n"ineerin"

2ail and 2oad >mban+mentsHridge Approaches and AbutmentsOffshore Hridge Abutments

Airport 2un&ays and :ai&ays'torage :an+s (%G, )rude Oil, %3G etc"3o&er 3lants


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'poh;4awan" !lectriied Double Track#*alaysia$


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'poh;4awan" !lectriied Double Track#*alaysia$

7 i


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5rid"e Approaches and Abutments

3utra5aya, 0alaysia


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(utra7aya 5rid"e Approach

!mbankment

L !"#$%

Top o& 'ridge (eck

'ored piles

Water Le)$ L !#"$*

3ile cap

EEmmbbaannkkmmeenntt

$C$ Structure

Stone columnsStone columns

L !+#$%

O h 5 id Ab


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Oshore 5rid"e Abutments

Iohor Hahru, 0alaysia

Ai 4 d T i


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Airport 4unways and Taiways

Alor 'etar Airport 3ro5ect, 0alaysia

S T k


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Stora"e Tanks

a;ira %G :erminal, Gu5arat


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Case ?istory o ?i"hway

!mbankment on Stone Column

Treated =round in @ueensland8Australia #Oh et al. -11$


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Subsoil (roperties


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Jntreated ') K 8m cc

') K m cc

! mm


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)ateral Displacement (roiles

Concl sions


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ConclusionsStone 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 bottom-

feed 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.


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Acknowled"ments

3rof. 0.2. 0adhav

3rofessor >meritus, I:Jisiting 3rofessor, ##: yderabad

4r. .2. 2a5u

0anaging 4irector@eller Asia


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!arth3uake 4ose

Thank Bou

Stone columns Anoverview 140117085610 Phpapp01

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