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Treatment of Peaty Clays using Grouted Stone Columns

Treatment of Peaty Clays usingTreatment of Peaty Clays usingTreatment of Peaty Clays using Treatment of Peaty Clays using Grouted Stone ColumnsGrouted Stone Columns

Dr. V. R. RajuDr. V. R. RajuManaging DirectorKeller Asia

Treatment of Peaty Clays using Grouted Stone Columns

ContentContento Introduction to Peaty Soils

o Common Treatment Solutions for Peaty Soil

o Introduction to Grouted Stone Columns (GSC)

o Applications of GSC

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Treatment of Peaty Clays using Grouted Stone Columns

Introduction to Introduction to Peaty SoilsPeaty Soils

Treatment of Peaty Clays using Grouted Stone Columns

Origin of PeatOrigin of Peat

Lake developed in low laying area

Plants grew along lake’s bank, Plants died &

Dead plants fill d th Plants died &

accumulated at the bottom of lake

filled up the entire lake

Swamp / Wetland

New plants grew, died & accumulated on top. Swamp / Wetland

become elevated. Peat layer is formed deep in the ground.

Source: www.roadex.org

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Treatment of Peaty Clays using Grouted Stone Columns

o Soil with organic content• Organic Soil (5% - 50% organic content)

What is Peat ?What is Peat ?

• Highly Organic Soil (> 50% organic content)

o In geotechnical engineering, “peat” refers to soils with more than 20% organic content.

o Typical Characteristics of Peat• Low bulk density (900 1 100 kg/m3)

Source: Peat Engineering Handbook by S.Noto

• Low bulk density (900 - 1,100 kg/m3)• High water content (200% - 2,000%)• High permeability / Large void ratio (e0 = 7.5-30)• Low shear strength• High compressibility• Highly acidic

Treatment of Peaty Clays using Grouted Stone Columns

Peaty ClayPeaty Clay

o Typical Characteristics of Peaty ClayClay• Organic Content (10 - 30 %)• Bulk density (1,300 - 1,500 kg/m3)• Water content (70 - 110%)• Shear strength (15 – 25 kPa)

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Treatment of Peaty Clays using Grouted Stone Columns

Common Treatment SolutionsCommon Treatment Solutionsfor Peaty Soilfor Peaty Soil

Treatment of Peaty Clays using Grouted Stone Columns

Remove & ReplaceRemove & ReplacePros :o Economicalo Economical

Cons :o Limited deptho Relatively slow for

large area D i io Dumping issues

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Treatment of Peaty Clays using Grouted Stone Columns

Pros :o Relatively

PVD & Heavy SurchargePVD & Heavy Surcharge

o Relatively economical

Cons :o Long treatment

periodo Large area treatment

Treatment of Peaty Clays using Grouted Stone Columns

Pros :o Low settlemento Load transfer to hard

PilingPiling

o Load transfer to hard stratum

o Does not require support of surrounding soil

Conso High costo High costo Requires use of

suspended slab

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Treatment of Peaty Clays using Grouted Stone Columns

Pros :o Improve Strength

Deep Soil Mixing (DSM)Deep Soil Mixing (DSM)

o Improve Strength, Stiffness & Permeability

o Deep treatment

Cons :o High Cement / limeo High Cement / lime

content required o Unpredictable strength

gain / Low strength

Treatment of Peaty Clays using Grouted Stone Columns

Effect of Cement mixing in Peaty soilEffect of Cement mixing in Peaty soil

UCS[MPa]

Clay

Sand

Cement content [kg/m3]

Peat

C ay

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Treatment of Peaty Clays using Grouted Stone Columns

Introduction toIntroduction toGrouted Stone Columns Grouted Stone Columns

Treatment of Peaty Clays using Grouted Stone Columns

Reinforcement using Stone ColumnsReinforcement using Stone Columns

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Treatment of Peaty Clays using Grouted Stone Columns

Penetration Material charging & Toe formation

ConstructingGSC

Construction Sequence of GSCConstruction Sequence of GSC

Treatment of Peaty Clays using Grouted Stone Columns

Vibrocat

EquipmentEquipment

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Treatment of Peaty Clays using Grouted Stone Columns

Completed GSCsCompleted GSCs

o Reinforcement by stiff, self-supporting columnscolumns

o Compaction of in-situ ground due to lateral displacement of GSC

Caution: Since the columns are unreinforced, they should not be subject to tension forces.

Treatment of Peaty Clays using Grouted Stone Columns

Key Aspects of GSC InstallationKey Aspects of GSC Installationo Installation is governed by BS EN 14731:2005, which require the use of

a deep vibratora deep vibrator.

o The compacted column has to be built up by adding successive discrete charges of specific granular material and compacting each one to a chosen level of power consumption, ensuring proper column compaction.

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Treatment of Peaty Clays using Grouted Stone Columns

Depth of treatment AmperageQuality ControlQuality Control

Charge of grouted stones

Column

Tim

e

o Real time monitoringColumn Construction

o Print-out of each GSC built

Treatment of Peaty Clays using Grouted Stone Columns

Load TestsLoad Tests

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Treatment of Peaty Clays using Grouted Stone Columns

Strength TestsStrength Tests

Treatment of Peaty Clays using Grouted Stone Columns

Applications of GSCApplications of GSC

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Treatment of Peaty Clays using Grouted Stone Columns

o High speed railway constructed adjacent existing railway embankment in Hamburg, Germany

GSC for Railway EmbankmentGSC for Railway Embankment

o Typical soil : 2.5m (Loose sand) and 3m (Organic clay)

o GSC to prevent long term settlement & address the embankment stability

Treatment of Peaty Clays using Grouted Stone Columns

GSC for REGSC for RE--WallWall

N b id b k t (4 lo New bridge embankment (4-lane driveway) in USA

o Height Fill-embankment ~ 3–8.5m

o GSC to prevent uneven settlement

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Treatment of Peaty Clays using Grouted Stone Columns

o 30-unit condominium in USA

o Soil : 5 5m of sandy fill and 4 0m of organic clay

GSC for Building raft foundationGSC for Building raft foundation

o Soil : 5.5m of sandy fill and 4.0m of organic clay

o GSC to improve bearing capacity and control settlements

Treatment of Peaty Clays using Grouted Stone Columns

GSC for Driveways

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Treatment of Peaty Clays using Grouted Stone Columns

DescriptionDescription

o ~865 m – Proposed Driveways

o Minimizing the settlement under 20 kPa load.

o Allowable settlement : 40mm

Treatment of Peaty Clays using Grouted Stone Columns

GSC Treatment SchemeGSC Treatment Scheme

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Treatment of Peaty Clays using Grouted Stone Columns

ConstructionConstruction

Treatment of Peaty Clays using Grouted Stone Columns

QA / QCQA / QC

Cube test

Plate Load test :o Settlement : 3 -11 mmo Average : 6 mm

Cube testo Strength : 8 – 25 MPa

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Treatment of Peaty Clays using Grouted Stone Columns

GSC for RC Tank Foundation

Treatment of Peaty Clays using Grouted Stone Columns

Jelutong Sewarage Treatment Planto Upgrading old sewerage system for Georgetown (Penang)

DescriptionDescription

o Sequential Batch Reactor (SBR) Tanks, with load = 96-126 kPa

o Allowable total settlement : 75mm

o Differential settlement < 1:360

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Treatment of Peaty Clays using Grouted Stone Columns

Aerial View of SiteAerial View of Site

Treatment of Peaty Clays using Grouted Stone Columns

Typical Soil ConditionTypical Soil ConditionDepth [m] Description Average

SPTFill Material: loose

0.00Fill Material: loose Silty Sand, occasionalrubbish

6 -10

5.00 Soft Silty Clay 3 -4

8.00 Medium Stiff Sandy Clay 6 -8

10.00 Stiff Sandy Clay 12 -16

15.00 Very Stiff Sandy Clay 1 20 -25

25.00 Very Stiff Sandy Clay 2 25 -30

40.00 Very Stiff Sandy Clay 3 30 -32

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Treatment of Peaty Clays using Grouted Stone Columns

Ground Improvement schemesGround Improvement schemes

Stone Column (SC(Grouted Stone Column (GSC)Deep Soil Mixing (DSM)

Treatment of Peaty Clays using Grouted Stone Columns

-5

00 5 10 15 20 25 30 35 40 45 50 55 60

Load (Tons)

QA / QCQA / QC

Jelutong STP Penang : VCC : SBR 4 - Column No. 1666

-25

-20

-15

-10

Settl

emen

t (m

m)

1st Cycle (100% - 35T) 2nd Cycle (125% - 44T) 3rd Cycle (150% - 52.5T)

00 25 50 75 100 125 150 175 200 225 250

Load (Tons)

o Max Load Test 150% : 52.5 T (single column)

Jelutong STP Penang : VCC : SBR 7 - Columns Nos. 825, 826, 860, 861

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

Settl

emen

t (m

m)

1st Cycle (100% - 140T 2nd Cycle (125% - 175T) 3rd Cycle (150% - 210T)

o Max Load Test 150% : 210 T

(4-column group)

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Treatment of Peaty Clays using Grouted Stone Columns

HydrotestHydrotestFull water Height:6.4m6.4m

Settlement :5 – 8 mm

Treatment of Peaty Clays using Grouted Stone Columns

Completed Sewerage Treatment PlantCompleted Sewerage Treatment Plant

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Treatment of Peaty Clays using Grouted Stone Columns

GSC for RC Tank Foundation

Treatment of Peaty Clays using Grouted Stone Columns

DescriptionDescriptionDesigned soil improvement under 3 biological blocks (125 x 35 each)

- Test fields

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Treatment of Peaty Clays using Grouted Stone Columns

DescriptionDescriptionPomorzany Waste Water Treatment Planto Located at Szczecin, Poland

Typical Soil ConditionTypical Soil ConditionDepth (m) Description

,o 3 nos Biological Tankso Load = 102 kPa

0 – 9 Filling9 – 10 Peat

10 – 12.3 Organic Mud12.3 – 19.8 Sand

Treatment of Peaty Clays using Grouted Stone Columns

DescriptionDescription

Field 2 (GSC) Field 1 (SC)

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Treatment of Peaty Clays using Grouted Stone Columns

ConstructionConstruction

Treatment of Peaty Clays using Grouted Stone Columns

Completed Water Treatment PlantCompleted Water Treatment Plant

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Treatment of Peaty Clays using Grouted Stone Columns

ConclusionsConclusions

o Peats and organic clays pose a special problems for engineers, because of exceptionally high water contents and decomposition p y g pwith time.

o Treatment with chemical binders (e.g. cement) has only limited effectiveness.

o Where removal is not possible, displacement using techniques such as vibro stone columns are suitable.

o In peaty soils it is often necessary to grout the stone column, to make them self-supporting

Treatment of Peaty Clays using Grouted Stone Columns

THANK YOUTHANK YOU