SOILS AND FOUNDATIONS Lesson 07 - ce.udel.edu 667 Geotech Design... · SOILS AND FOUNDATIONS...

SOILS AND FOUNDATIONSSOILS AND FOUNDATIONS

Testing

Experience

Theory

Lesson 07Lesson 07Chapter 7 Chapter 7 –– Approach Roadway DeformationsApproach Roadway Deformations

TopicsTopics

ggTopic 1 (Section 7.0 to 7.6)Topic 1 (Section 7.0 to 7.6)-- Approach roadway deformationsApproach roadway deformations

ggTopic 2 (Section 7.7, 7.8, 7.9)Topic 2 (Section 7.7, 7.8, 7.9)-- Mitigation of approach roadway deformationMitigation of approach roadway deformation-- Construction monitoring and quality assuranceConstruction monitoring and quality assurance

APPROACH ROADWAY APPROACH ROADWAY DEFORMATIONSDEFORMATIONS

Lesson 07 Lesson 07 -- Topic 1Topic 1Approach Roadway DeformationsApproach Roadway Deformations

Section 7.0 Section 7.0 –– 7.67.6

Learning OutcomesLearning Outcomes

gg At the end of this session, the participant will be At the end of this session, the participant will be able to:able to:-- Contrast internal and external deformationContrast internal and external deformation-- Recall techniques to minimize internal deformationRecall techniques to minimize internal deformation-- Compute vertical stress distribution beneath Compute vertical stress distribution beneath

embankmentsembankments-- Calculate settlement in coarseCalculate settlement in coarse--grained soilsgrained soils-- Calculate consolidation settlement magnitude and time in Calculate consolidation settlement magnitude and time in

finefine--grained soilsgrained soils-- Compare immediate, primary and secondary settlementsCompare immediate, primary and secondary settlements-- Discuss lateral squeezeDiscuss lateral squeeze

Stresses Imposed by StructuresStresses Imposed by Structures

ggThe approach embankments induce stresses The approach embankments induce stresses in the foundation soilin the foundation soil

Approach Roadway EmbankmentsApproach Roadway EmbankmentsMajor Design ConsiderationsMajor Design ConsiderationsggStabilityStabilityggDeformationsDeformations

-- VerticalVertical-- LateralLateral

ggEffects on the StructureEffects on the Structure-- Bump at the end of the bridgeBump at the end of the bridge-- TiltingTilting

Stability ProblemsStability Problems

Embankment Fill

Firm Soil

ggShallow Shallow translational translational failure (Infinite failure (Infinite Slope)Slope)

ggCircular Circular FailureFailure

Stability ProblemsStability Problems

ggSliding Sliding block block failurefailure

ggLateral Lateral squeezesqueeze-- Lesson 7Lesson 7

Approach Roadway DeformationsApproach Roadway Deformations

gg InternalInternal-- Within the embankment fillWithin the embankment fill

•• Due to compression of the fill materialsDue to compression of the fill materials•• Poor drainagePoor drainage

ggExternalExternal-- In the native soils below the embankment fillIn the native soils below the embankment fill

•• Vertical and lateral deformation of native soilsVertical and lateral deformation of native soils•• Vertical: Immediate and consolidation settlementsVertical: Immediate and consolidation settlements•• Lateral: Squeeze (cause tilting of structures)Lateral: Squeeze (cause tilting of structures)

Internal DeformationsInternal Deformations

Avoiding Internal DeformationsAvoiding Internal Deformations

ggNo organic or miscellaneous fill material No organic or miscellaneous fill material allowedallowed

ggControl fineControl fine--grained material usegrained material useggRequire compaction with proper moisture Require compaction with proper moisture

control control ggCompaction control testsCompaction control tests

To Eliminate Internal DeformationsTo Eliminate Internal Deformations

Select Structure Fill (100% T99)

Highway Embankment Material (90% T180)

Highway Embankment Material 6” Topsize (95% T180)

Suggested Approach Embankment Details (Figure 7-1)

6” Topsize

90% T180

50’ Minimum

5’ 100% T99

1

1

3

11

1

Bump at the End of a BridgeBump at the End of a Bridge

Reasons for “the Bump at the Reasons for “the Bump at the End of the Bridge”End of the Bridge”ggPoor compaction of embankment material Poor compaction of embankment material

near the structurenear the structureggMigration of fines into drainage material Migration of fines into drainage material

behind abutment behind abutment backwallbackwall

ggWhat is the solution?What is the solution?ggApproach slabApproach slab

““Bump at the End of the Bump at the End of the Approach Slab”Approach Slab”

To Prevent Bump at End of Bridge To Prevent Bump at End of Bridge

gg Use select structural fillUse select structural fillgg Use Use underdrainunderdrain filter filter

material material gg Use durable well Use durable well

graded granular for graded granular for high density w/min. high density w/min. compactivecompactive effort effort

gg Figure 7Figure 7--22

Underdrain Filter Material (6” Lifts)

Select Structural Fill (100 % T99)

Heel Projection + 3 ft

1’6”

Select Material SpecificationsSelect Material Specifications

ggSpecification ItemSpecification Item-- 6”6”--8” Lift Thickness8” Lift Thickness

-- Topsize RestrictionTopsize Restriction

-- Gradation RequirementGradation Requirement

-- Limit Percent FinesLimit Percent Fines

ggReason for ItemReason for Item-- Small Compaction Small Compaction

EquipmentEquipment

-- Less than 3/4 Lift Less than 3/4 Lift ThicknessThickness

-- CompactibilityCompactibility

-- Density/PipingDensity/Piping

Select Material Specification (Cont’d)Select Material Specification (Cont’d)

ggSpecification ItemSpecification Item-- DurabilityDurability

-- T99 Density ControlT99 Density Control

-- Compatible to Drain Compatible to Drain MaterialMaterial

ggReason for ItemReason for Item-- Minimize BreakdownMinimize Breakdown

-- Small Compaction Small Compaction EquipmentEquipment

-- Prevent PipingPrevent Piping

External DeformationsExternal Deformations

Avoid Major Subsoil SettlementAvoid Major Subsoil Settlement

gg Identify and provide treatment for organic Identify and provide treatment for organic soilssoils

ggAnalyze clay subsoil depositsAnalyze clay subsoil deposits

Types of DeformationsTypes of Deformations

gg Immediate (shortImmediate (short--term) deformationterm) deformationggConsolidation (longConsolidation (long--term) deformationterm) deformation

gg Immediate deformation occurs in ALL soils Immediate deformation occurs in ALL soils whether cohesive or whether cohesive or cohesionlesscohesionless

ggConsolidation deformation occurs only in Consolidation deformation occurs only in fine grained soils that are saturated at the fine grained soils that are saturated at the time of application of loadstime of application of loads

First Step in Evaluation of First Step in Evaluation of DeformationsDeformationsggUnder applied external loadings, estimate Under applied external loadings, estimate

the stress distribution with depththe stress distribution with depth

ggChapter 2: Stress and Strain in SoilsChapter 2: Stress and Strain in Soils-- Section 2.5Section 2.5-- Section 2.6Section 2.6

Vertical Vertical Stress Due Stress Due to External to External LoadingsLoadings

p = γthh

0.6p

0.4p

0.8p

0.2p

ggDepth of Depth of Significant Significant Influence Influence (DOSI), D(DOSI), Dss

Do you think there is a settlement Do you think there is a settlement problem for the case shown below?problem for the case shown below?

Soft Clay

Granular Fill

γ = 120 pcf24’

23’Sandy Gravel

γ = 120 pcf (γ’ = 60 pcf)

Sand6’

Combined Plot of StressesCombined Plot of StressesFigure 2Figure 2--1313

zw

po pt

Δp

Pressure

Depth, z

Legend:zw = depth to groundwaterpo = effective overburden pressurept = total overburden pressureΔp = pressure due to external loadspf = p0 + Δp

pf

Fundamental PrinciplesFundamental Principles

ggStresses induced in the soil from an Stresses induced in the soil from an embankment load are distributed with depth embankment load are distributed with depth in proportion to embankment widthin proportion to embankment width

ggThe additional stresses in the soil decrease The additional stresses in the soil decrease with depthwith depth

Stress Stress Distribution Distribution Under FillsUnder Fills

In each chart, the upper line gives the pressure under the centerline while the lower line gives the pressure under the mid-point of the side slope

ggSection 7.3.1Section 7.3.1ggFigure 7Figure 7--33

Example 7Example 7--11

ggFind the stress increase (Find the stress increase (ΔΔp) under the proposed p) under the proposed abutment abutment centroidcentroid (Point X) at a depth of 0.8 b(Point X) at a depth of 0.8 bffbelow the base of the fillbelow the base of the fill

Point X

30′ bf = 80′ 1

2

60′ 100′

hf

bf

Fill height hf = 30 ft; End and side slopes (1V:2H)Embankment top width =100 ft; Fill unit weight γf = 100 pcf

Stress Distribution Under FillsStress Distribution Under Fillsgg bbff=(100 ft /2) + (60 ft/2) = 80 ft=(100 ft /2) + (60 ft/2) = 80 ftgg Use chart for 0.8bUse chart for 0.8bff = 0.8 (80 ft)=64 ft and a distance = 0.8 (80 ft)=64 ft and a distance

measured from midmeasured from mid--point of end slope to Point X as multiple point of end slope to Point X as multiple of bof bff =(30 ft/80 =(30 ft/80 ft)bft)bff = 0.38b= 0.38bff

gg KKff=0.7=0.7gg ΔΔp= p= KKffγγffhhff = (0.7)(100 pcf)(30 ft)== (0.7)(100 pcf)(30 ft)=2,100 2,100 psfpsf

0.5

Mid Point ofEnd Slope

1.0

Mid Point ofSide Slope

0

1.0bf 0.5bf 0.5bf 1.0bf

Centerline0.38b

0.7

0.8bf = 64 ftDepth Below SurfacePr

essu

re C

oeff

icie

nt K

f

Computation of Immediate Computation of Immediate Settlement (Vertical Deformation)Settlement (Vertical Deformation)ggMany methods for estimating immediate Many methods for estimating immediate

settlement are availablesettlement are available

ggAll methods are based on some form of All methods are based on some form of estimate of soil compressibilityestimate of soil compressibility-- “Bearing Capacity Index”, “Compression Index”, “Bearing Capacity Index”, “Compression Index”,

“Elastic Modulus”, “Constrained Modulus”, etc.“Elastic Modulus”, “Constrained Modulus”, etc.

Computation of Immediate Computation of Immediate Settlement (Vertical Deformation)Settlement (Vertical Deformation)ggFor embankments use Hough’s methodFor embankments use Hough’s method

-- Simple to useSimple to use-- Settlement estimates are conservative by a Settlement estimates are conservative by a

factor of 2 (FHWA 1987)factor of 2 (FHWA 1987)

ggFor footings use more refined methodsFor footings use more refined methods-- SchmertmannSchmertmann (1978) (1978) ------------ Chapter 8Chapter 8

•• Considers strain distribution with depthConsiders strain distribution with depth-- D’AppoloniaD’Appolonia (1968)(1968)

•• Considers effect of Considers effect of preconsolidationpreconsolidation

Hough’s MethodHough’s Method

Step 1:Step 1: Determine bearing capacity index, CDetermine bearing capacity index, C′′,,Use N1Use N16060 value in Hough’s chartvalue in Hough’s chart

Step 2:Step 2: Subdivide soil layer into 10 ft Subdivide soil layer into 10 ft ±±increments and sum settlements for increments and sum settlements for all layers using following equation all layers using following equation for each layerfor each layer

0

010 p

Δpplog

C1HΔH

+⎟⎠⎞

⎜⎝⎛

′=

Hough’s ChartHough’s Chart

gg Inorganic SILT Inorganic SILT curve should curve should not be used for not be used for soils exhibiting soils exhibiting plasticityplasticity

CORRECTED SPT N-VALUE, N160


ggDetermine immediate settlement of a wide Determine immediate settlement of a wide embankment placed on embankment placed on siltysilty sandsand

20 ft

10 ft

γt = 120 pcf

Silty Sand γt = 120 pcf, N160 = 20

Example 7Example 7--2 2 –– Draw Draw ppoo diagramdiagramggAssume no dissipation of stress under the Assume no dissipation of stress under the

centerline of a “wide” embankmentcenterline of a “wide” embankment

pf po

0

Depth (ft)

Pressure (psf)

4000 3000 2000 1000

10

5 600 3000

Δp = 2400

Example 7Example 7--2 2 –– Draw Draw ppoo diagramdiagram

ggFor For N1N16060 = 20= 20 and and SiltySilty Sand, CSand, C′′ ≈≈ 58 from 58 from Figure 7Figure 7--4 (Hough4 (Hough’’s chart) s chart)

ggFind settlementFind settlement

600psf2400psf600psflog

581ft10ΔH 10

+⎟⎠⎞

⎜⎝⎛=

in1.44ft0.12ΔH ==

0

010 p

Δpplog

C1HΔH

+⎟⎠⎞

⎜⎝⎛

′=

Vertical Vertical Stress Due Stress Due to External to External LoadingsLoadings

p = γthh

0.6p

0.4p

0.8p

0.2p

gg Note the Note the variation of variation of vertical vertical stress under stress under a narrow a narrow embankmentembankment

Implications of Embankment Implications of Embankment SettlementSettlementggAt end of embankment construction, At end of embankment construction,

additional fill is required to reach final gradeadditional fill is required to reach final gradegg1 inch of settlement over 1 mile of 601 inch of settlement over 1 mile of 60--ft wide ft wide

embankment will need approximately 1000 embankment will need approximately 1000 cubic yards of additional fillcubic yards of additional fill

ggThis is sometimes referred to as This is sometimes referred to as “Compaction Factor” and is included in bid “Compaction Factor” and is included in bid documentsdocuments

Student Exercise 3Student Exercise 3gGIVEN: po values at the depths where SPTs

were taken; Soil is fine to coarse sand

Depth, ft SPT N60-values po (psf)5 6 550

10 10 110015 15 165020 17 220025 16 2438

gFIND: (a) N160 value(b) C′ (bearing capacity index) value

Student ExerciseStudent Exercise

ggSolutionSolution

Consolidation (LongConsolidation (Long--term) Deformationterm) Deformation

ggConsolidation deformation occurs only in Consolidation deformation occurs only in fine grained soils that are saturated at the fine grained soils that are saturated at the time of application of loadstime of application of loads

ggLaboratory estimates of settlements are Laboratory estimates of settlements are often inaccurateoften inaccurate

ggUse consolidation approach when S > 90%Use consolidation approach when S > 90%ggEffect of consolidation is 3Effect of consolidation is 3--D for limited D for limited

loaded areas typical of transportation loaded areas typical of transportation structuresstructures

Lateral Lateral Stress Due Stress Due to External to External LoadingsLoadingsggNote Lateral Note Lateral

Stresses Stresses Beyond Beyond Loaded Loaded AreaArea

Zone of Tensile Stresses

0.2p

0.4p0.6p

p = γthh

SoftLayer

Consolidation (LongConsolidation (Long--term) Deformationterm) Deformation

ggVertical component of 3Vertical component of 3--D D consoldationconsoldation is is estimated based on data from 1estimated based on data from 1--D laboratory D laboratory consolidation testconsolidation test

ggChapter 5, Section 5.4Chapter 5, Section 5.4

Normally Consolidated SoilsNormally Consolidated Soils

VERTICAL EFFECTIVE STRESS σ' v (LOG SCALE)

e = eo p

e f

o0.42e

(a)

Cc

1

VO

ID R

ATI

O, e

σ' = σ' p vo

Δσ' v

σ' vf

⎟⎟⎠

⎞⎜⎜⎝

⎛+

=∑o

f10o

n

i o

cc p

p log H

e1C

S

pfpo = pc

Δp

p

Over Consolidated (Over Consolidated (PreconsolidatedPreconsolidated) ) SoilsSoils

)pp log C

pp logC (

e 1H S

c

f10c

o

c10r

o

on

1+

+∑=

VERTICAL EFFECTIVE STRESS σ' v (LOG SCALE)

0.42e o

(a)

VO

ID R

ATI

O, e

e f

e p

c

1

C

Δσ' v vfσ'

o e1

γC

pσ'

σ' vo

pc

po Δp pf

p

Under Consolidated SoilsUnder Consolidated Soils

)pp

log C pp logC (

e 1H S

0

f10c

c

010c

o

on

1+

+∑=

VERTICAL EFFECTIVE STRESS p(LOG SCALE)

VO

ID R

ATI

O

ef

p

c1

C

1rC

σ´v 0σ´p

Δσ´v0

σ´v f

Δσ ve0

e

Δp

pc po pf

Δpo

Time Rate of ConsolidationTime Rate of Consolidation

SettlementSettlement--Time RelationshipTime Relationship

where:where:

t = Time for Settlementt = Time for Settlement

TTvv = Time Factor (dimensionless)= Time Factor (dimensionless)

HHdd = Vertical Drainage Path Length= Vertical Drainage Path Length

ccvv= Coefficient of Consolidation (e.g., ft= Coefficient of Consolidation (e.g., ft22/day)/day)

v

2dv

cHTt =

Embankment on Clay Subsoil Embankment on Clay Subsoil TimeTime--Settlement CurveSettlement Curve

Time (Months)Time (Months)11 22 33 44 55 66 77 88 99

00

1.01.02.02.0

3.03.0

4.04.0

5.05.0

6.06.0

7.07.0

Settl

emen

t (In

ches

)Se

ttlem

ent

(Inch

es)


ggDetermine magnitude and the time for 90% Determine magnitude and the time for 90% consolidation for the primary settlementconsolidation for the primary settlement

20′

10′

γt = 120 pcf

Clay (Normal Consolidated) γt = 120 pcf,

Cc = 0.5, e0 = 1.0, cv = 0.2 dayft 2

Rock


ggppoo diagramdiagram

pf po

0

Depth (ft)

Pressure (psf)

4000 3000 2000 1000

10

5 600 3000

Δp = 2400


ggFind primary settlementFind primary settlement

0

010

0

c

pΔpp

loge1

CHΔH

++

=

inches21ft75.1psf600

psf2400psf60010log

1.010.5ft10ΔH ==

+⎟⎠⎞

⎜⎝⎛

+=


ggFind time for 90% consolidation. Assume Find time for 90% consolidation. Assume single drainage due to impervious rock single drainage due to impervious rock underlying clay layer. Use underlying clay layer. Use

vc

2dHvT

90t =

days424day/ft2.0

)ft10)(848.0(t 2

290 ==

Student Student Exercise 4Exercise 4

Soil Profile

Pressure Diagram

24'

23'

6'

Granular Fill= 120 pcf

Sandy Gravel

T = 122 pcf

Soft Clay T = 104 pcf, e = 2.1, Cc = 1.1Sando Cv = 0.0175 ft2 /day

24'

23'

6'

Granular Fill= 120 pcf

Sandy Gravel

T = 122 pcf

Soft Clay T = 104 pcf, e = 2.1, Cc = 1.1Sando Cv = 0.0175 ft2 /day

po pF

Middle of clay layer

SandyGravel

ClayΔp

23’

29’

po pF

Middle of clay layer

SandyGravel

ClayΔp

23’

29’

Compute:Compute:(a)(a) Primary Primary

settlement settlement of NC clayof NC clay

(b)(b) Time in Time in months for months for 90% 90% primary primary settlementsettlement

Secondary CompressionSecondary Compression

ggSee Section 7.5.4See Section 7.5.4

Lateral SqueezeLateral Squeeze

Fill

be

Lateral Lateral SqueezeSqueezeggShortShort--term term

undrainedundrainedbearing bearing capacity capacity failurefailure

ggLongLong--term term drained 3drained 3--D D creepcreep

Zone of Tensile Stresses

0.2p

0.4p0.6p

p = γthh

SoftLayer

Abutment Tilting Due to Lateral Abutment Tilting Due to Lateral SqueezeSqueeze

Rotation of RockersRotation of Rockers

((γγFILLFILL)(H )(H FILLFILL) > 3c) > 3cuu

Threshold Condition for Lateral Threshold Condition for Lateral SqueezeSqueeze

Safety Factor against Lateral SqueezeSafety Factor against Lateral Squeeze

⎥⎦

⎤⎢⎣

⎡γ

+⎥⎦

⎤⎢⎣

⎡θγ

=H

c14.4tanDc2FS u

S

uSQ

Get fill settlement out before abutment deep Get fill settlement out before abutment deep foundations are constructedfoundations are constructed

Lateral Squeeze: Lateral Squeeze: How to Prevent Abutment RotationHow to Prevent Abutment Rotation


gg At the end of this session, the participant will be At the end of this session, the participant will be able to:able to:-- Contrast internal and external deformationContrast internal and external deformation-- Recall techniques to minimize internal deformationRecall techniques to minimize internal deformation-- Compute vertical stress distribution beneath Compute vertical stress distribution beneath

embankmentsembankments-- Calculate settlement in coarseCalculate settlement in coarse--grained soilsgrained soils-- Calculate consolidation settlement magnitude and time in Calculate consolidation settlement magnitude and time in

finefine--grained soilsgrained soils-- Compare immediate, primary and secondary settlementsCompare immediate, primary and secondary settlements-- Discuss lateral squeezeDiscuss lateral squeeze

Any Questions?Any Questions?

THE ROAD TOUNDERSTANDING

SOILSAND

FOUNDATIONS

APPROACH ROADWAY APPROACH ROADWAY DEFORMATIONSDEFORMATIONS

Lesson 07 Lesson 07 -- Topic 2Topic 2Mitigation of Approach Roadway DeformationsMitigation of Approach Roadway DeformationsConstruction Monitoring and Quality AssuranceConstruction Monitoring and Quality Assurance

Section 7.7, 7.8, 7.9Section 7.7, 7.8, 7.9


ggAt the end of this session, the participant will At the end of this session, the participant will be able to:be able to:-- Recall techniques for reducing settlement Recall techniques for reducing settlement

magnitudemagnitude-- Describe techniques for reducing time rate of Describe techniques for reducing time rate of

settlementsettlement-- Identify types of performance monitoring Identify types of performance monitoring

instrumentationinstrumentation-- Discuss importance of proper compactionDiscuss importance of proper compaction

Solutions for Settlement ProblemsSolutions for Settlement Problems

ggReduce Amount of SettlementReduce Amount of Settlement-- Category 1: Increasing the resistanceCategory 1: Increasing the resistance-- Category 2: Reducing the loadCategory 2: Reducing the load

ggReduce Settlement TimeReduce Settlement Time-- SurchargeSurcharge-- Vertical DrainsVertical Drains

Reduce Amount of SettlementReduce Amount of Settlement

ggCategory 1: Increasing the resistanceCategory 1: Increasing the resistance-- Excavation and Excavation and recompactionrecompaction-- Excavation and replacementExcavation and replacement-- Vertical inclusions, e.g., stone columnsVertical inclusions, e.g., stone columns-- Horizontal inclusions, e.g., geosyntheticsHorizontal inclusions, e.g., geosynthetics-- GroutingGrouting-- Dynamic compactionDynamic compaction

Reducing Amount of SettlementReducing Amount of Settlement

ggCategory 2: Reducing the loadCategory 2: Reducing the load-- Reduce grade lineReduce grade line-- Use lightweight fill, e.g., expanded shale, foamed Use lightweight fill, e.g., expanded shale, foamed

concrete, concrete, geofoamgeofoam-- Bypass soft layer with a deep foundationBypass soft layer with a deep foundation

•• Need load transfer platformNeed load transfer platform

Reducing Settlement TimeReducing Settlement Time

ggSurcharge treatmentSurcharge treatmentggVertical drainsVertical drains

Embankment on Clay FoundationEmbankment on Clay FoundationEffect of Surcharge TreatmentEffect of Surcharge Treatment

Without SurchargeWithout Surcharge

With SurchargeWith Surcharge

TimeTime Time for Total Settlement Without SurchargeTime for Total Settlement Without Surcharge

Time for Equivalent Settlement With Surcharge – Remove Surcharge at This Time

Time for Equivalent Settlement With Surcharge – Remove Surcharge at This Time

Settl

emen

tSe

ttlem

ent

SurchargeSurcharge

ClayClay

FillFill

Acceleration of Consolidation Acceleration of Consolidation Using Vertical DrainageUsing Vertical Drainage

Sand

Clay

Vertical DrainsVertical Drains

Settlement Platform Settlement Platform

Permanent Fill Permanent Fill

Soft Clay Soft Clay

Vertical Vertical Drain Drain

Surcharge Surcharge

Drainage Blanket Drainage Blanket

Piezometers Piezometers

Firm Soil Firm Soil

Not to ScaleNot to Scale

gg Position rig at drain locationPosition rig at drain locationgg Place anchor on drain endPlace anchor on drain endgg Penetrate mandrel to desired depthPenetrate mandrel to desired depthgg Withdraw mandrelWithdraw mandrelgg Cut drain material above drainage blanketCut drain material above drainage blanket

Vertical Drain Installation Vertical Drain Installation SequenceSequence

Construction Monitoring and QAConstruction Monitoring and QA

ggClearly specify line and grade on plansClearly specify line and grade on plansggDo not make frequent changes in details Do not make frequent changes in details

because repetition makes construction because repetition makes construction easiereasier

ggMake sure that embankments are compacted Make sure that embankments are compacted to meet the compaction requirements and to meet the compaction requirements and limits noted on the planslimits noted on the plans

Construction Monitoring by Construction Monitoring by InstrumentationInstrumentationggPiezometersPiezometersggSettlement platesSettlement platesgg InclinometersInclinometers

Typical Instrumentation PlanTypical Instrumentation Plan

Fill S.I. S.I.Original Ground

Soft Clay

Firm Soil Piezometers Settlement Plate Slope Inclinometer S.I.

H 4H

2H

H43

Settlement Platform SchematicSettlement Platform Schematic

Vertical InclinometerVertical Inclinometer

Embankment

Compressible Soil

Firm Soil

Principle of Inclinometer OperationPrinciple of Inclinometer Operation

ΣL Sinθ

L Sinθ

L θ

L = Distance between readings θ = Angle measured by sensor

PiezometerPiezometer

Compressible Soil

Embankment


ggAt the end of this session, the participant will At the end of this session, the participant will be able to:be able to:-- Recall techniques for reducing settlement Recall techniques for reducing settlement

magnitudemagnitude-- Describe techniques for reducing time rate of Describe techniques for reducing time rate of

settlementsettlement-- Identify types of performance monitoring Identify types of performance monitoring

instrumentationinstrumentation-- Discuss importance of proper compactionDiscuss importance of proper compaction



SOILSAND

FOUNDATIONS

Interstate 0 Interstate 0 –– Apple FreewayApple FreewayNote: Scale shown in Station FormNote: Scale shown in Station Form

Baseline Stationing

Baseline Stationing

S.B. Apple Frwy

N.B. Apple Frwy

Proposed Toe of SlopeProposed Toe of Slope

Existing Ground SurfaceExisting Ground Surface

12

Proposed Final GradeProposed Final GradeProposed AbutmentProposed Abutment

Interstate 0Interstate 0

9090 9191 9292 9393

Apple Freeway Apple Freeway ExerciseExerciseggAppendix AAppendix A

-- Section A.6Section A.6

Subsurface Explorations

Terrain reconnaissance Site inspection Subsurface borings

Basic Soil Properties Visual description

Classification tests Soil profile

Laboratory Testing Po diagram

Test request Consolidation results Strength results

Slope Stability

Design soil profile Circular arc analysis Sliding block analysis Lateral squeeze analysis

Approach Roadway Deformations

Design soil profile Magnitude and rate of settlement Surcharge Vertical drains

Spread Footing Design

Design soil profile Pier bearing capacity Pier settlement Abutment settlement Surcharge Vertical drains

Driven Pile Design Design soil profile

Static analysis – pier Pipe pile H – pile Static analysis – abutment Pipe pile H – pile Driving resistance Lateral movement - abutment

Construction Monitoring

Wave equation Hammer approval Embankment instrumentation

Design Soil Profile (East Approach Design Soil Profile (East Approach Embankment Settlement)Embankment Settlement)

2:1Fill

= 130 pcf= 400

c = 030'

3'7'

35'

Organic = 90 pcf w = 120% s.g. = 1.6

Sand = 110 pcf N = 17= 50pcf C' = 90

5'

Clay= 65 pcf

Cc = 0.35Cr = 0.035Cv = 0.6 ft 2 /dayw = 35%

s.g. = 2.78

Incompressible

2:1Fill

= 130 pcf= 400

c = 030'

3'7'

35'

Organic = 90 pcf w = 120% s.g. = 1.6

Sand = 110 pcf N = 17= 50pcf C' = 90

5'

Clay= 65 pcf

Cc = 0.35Cr = 0.035Cv = 0.6 ft 2 /dayw = 35%

s.g. = 2.78

Incompressible

pc

Po Diagram Pressure (psf)0 1000 2000 3000 4000 5000 6000

10

20

30

40po

xx

x

x

xx

x

x

x

x

135 4100

570

1020

1630

4460

4950

5300

58003600 pFx

OrganicSand

x4450Clay

2460

pc

Po Diagram Pressure (psf)0 1000 2000 3000 4000 5000 6000

10

20

30

40po

xx

x

x

xx

x

x

x

x

135 4100

570

1020

1630

4460

4950

5300

58003600 pFx

OrganicSand

x4450Clay

2460x

OrganicSand

x4450Clay

2460

Compute Total SettlementCompute Total Settlement

Total Settlement

Layer 1 - Organic (0' -3')

Layer 2 - Sand (3' - 10')

Layer 3 - Clay (10' - 18')

Clay (18' - 28')

Clay (28' - 45')

19.54"

0.83"

1.17"

2.55"

8.11"

Total 32.20"H

Total Settlement

Layer 1 - Organic (0' -3')

Layer 2 - Sand (3' - 10')

Layer 3 - Clay (10' - 18')

Clay (18' - 28')

Clay (28' - 45')

19.54"

0.83"

1.17"

2.55"

8.11"

Total 32.20"H

TimeTime--Settlement PlotSettlement Plot

100

90

Time - Settlement Plot

100 200 300 400 500

5

10

15

Time (days)

11.39"for sand +for clay

@ 433 days)

12.66" (max. H)

0.83

100

90


100 200 300 400 500

5

10

15

Time (days)

11.39"for sand +for clay

@ 433 days)

12.66" (max. H)

0.83

Assume:10’ high compacted surcharge ( = 130 pcf)Δ P of emb. (PF) + surch. (Ps) = 5200 psf

Assume:10’ high compacted surcharge ( = 130 pcf)Δ P of emb. (PF) + surch. (Ps) = 5200 psf


30’ Fill + 10’ Surcharge

180 Days


30’ Fill + 10’ Surcharge

180 Days

Recheck stability of 30’ Fill With 10' SurchargeF.S. = 1.33Bishop

Fill33'

7' Sand

35' Clay

DenseGravel

10'

25'

2:1

F.S. w/surcharge = 1.33 (1.63 w/o surcharge)

Recheck stability of 30’ Fill With 10' SurchargeF.S. = 1.33Bishop

Fill33'

7' Sand

35' Clay

DenseGravel

10'

25'

2:1Fill33'

7' Sand

35' Clay

DenseGravel

10'

25'

2:1

F.S. w/surcharge = 1.33 (1.63 w/o surcharge)


100 200 300 400 500

5

10

15

Time (days)

0.83

12.66"

180days

30' Fill

30' Fill + 10' Surcharge30' Fill w/Drains

Treatment

Fill only

Fill w/10' surcharge

fill w/ wick drain

90 (mo.)

14

6

2

Extra Cost

-

$120,000

$172,000

t


100 200 300 400 500

5

10

15

Time (days)

0.83

12.66"

180days

30' Fill



100 200 300 400 500

5

10

15

Time (days)

0.83

12.66"

180days

30' Fill


Treatment

Fill only

Fill w/10' surcharge

fill w/ wick drain

90 (mo.)

14

6

2

Extra Cost

-

$120,000

$172,000

t

SummarySummary Design Soil Profile

Soil layer consolidationproperties selected

Settlement

Vertical Drains

60 days for t90Cost $172,000 -> $385,000

Cost $120,000, F.S. = 1.33 O.K.10' surcharge improves t90 to 190 days

Time-Rate

Surcharge

32" settlement predictedRecommend organic excavationRec. waiting period @ abut.

433 days for t90

Design Soil Profile

Soil layer consolidationproperties selected

Settlement

Vertical Drains

60 days for t90Cost $172,000 -> $385,000

Cost $120,000, F.S. = 1.33 O.K.10' surcharge improves t90 to 190 days

Time-Rate

Surcharge

32" settlement predictedRecommend organic excavationRec. waiting period @ abut.

433 days for t90



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