Correlations for Coefficient of Correlations for Coefficient of Consolidation, Consolidation, ccvvggFigure 5Figure 5--1010

Correlations for Coefficient of Correlations for Coefficient of Secondary Compression, CSecondary Compression, Cαα

ggFigure 5Figure 5--1111

Shear Strength of SoilsShear Strength of Soils

ggStrength due to frictionStrength due to frictionggStrength due to cohesionStrength due to cohesion

-- True cohesionTrue cohesion-- Apparent cohesionApparent cohesion-- BE CAREFUL OF USING COHESION IN DESIGNBE CAREFUL OF USING COHESION IN DESIGN

ggTable 5Table 5--88

Laboratory Shear Strength TestsLaboratory Shear Strength Tests

ggUnconfined compression testUnconfined compression testggTriaxialTriaxial compression testcompression testggDirect shear testDirect shear test

Unconfined Compression TestUnconfined Compression Test

ggUndrainedUndrained testtestggUnconfined compressive Unconfined compressive

strength, strength, qquu

ggUndrainedUndrained shear shear strength, strength, ssuu

ggssuu = q= quu/2/2ggCannot simulate depth Cannot simulate depth

effecteffect

Axial Stress

Axial Stress

Cylindrical Soil Sample

TriaxialTriaxial Compression TestCompression Test

Axial Stress

Axial Stress

Confining(lateral) Stress

TriaxialTriaxial Compression TestCompression Test

Types of Types of TriaxialTriaxial Compression TestsCompression Tests

ggUnconsolidatedUnconsolidated--UndrainedUndrained (UU)(UU)ggConsolidatedConsolidated--Drained (CD)Drained (CD)ggConsolidatedConsolidated--UndrainedUndrained (CU)(CU)

UnconsolidatedUnconsolidated--UndrainedUndrained (UU) Test(UU) Test

ggNo consolidation under confining pressureNo consolidation under confining pressureggNo drainage during shearNo drainage during shearggGives Gives undrainedundrained shear strength, shear strength, ssuu

ggModels rapid loading conditionsModels rapid loading conditions-- e.g., rapid construction of embankment over soft e.g., rapid construction of embankment over soft

clayclay

ConsolidatedConsolidated--Drained (CD) TestDrained (CD) Test

ggComplete consolidation under confining Complete consolidation under confining stressstress

ggApply shear stress at a slow rate so that Apply shear stress at a slow rate so that there is no buildthere is no build--up of excess pore water up of excess pore water pressurepressure

ggTest may take several months for low Test may take several months for low permeability soilspermeability soils

ggGives effective stress parameters, Gives effective stress parameters, cc′′ and and φφ′′

ConsolidatedConsolidated--UndrainedUndrained (CU) Test(CU) Test

gg Allow sample to consolidate under confining Allow sample to consolidate under confining pressurepressure

gg Shear without allowing drainage but measure the Shear without allowing drainage but measure the excess pore water pressure (u)excess pore water pressure (u)

gg Can obtain both total and effective stress Can obtain both total and effective stress parameters, parameters, -- cc′′ and and φφ′′-- ccuu and and φφuu

gg Test can be performed in a reasonable time frameTest can be performed in a reasonable time frame

Direct Shear TestDirect Shear Test

Normal Force, N

Tangential Shear Force, T

Side of bottom box fixed against lateral movement

Sample

Predetermined failure (shear) plane

Direct Shear TestDirect Shear Test

Direct Shear TestDirect Shear Test

ggPredetermined failure planePredetermined failure planeggNo way to control confining pressureNo way to control confining pressureggNo way to measure excess pore water No way to measure excess pore water

pressurepressureggUse is generally limited to Use is generally limited to cohesionlesscohesionless soils soils

or compacted soilsor compacted soilsggUseful for interface testing (e.g., Useful for interface testing (e.g.,

geosyntheticgeosynthetic liners)liners)

Comparison of Laboratory and Field Comparison of Laboratory and Field StrengthsStrengthsggField Vane Shear TestsField Vane Shear Tests

Correlations of Shear Strength with Correlations of Shear Strength with Index ParametersIndex ParametersggUndrainedUndrained Shear StrengthShear Strength

Correlations of Shear Strength with Correlations of Shear Strength with Index ParametersIndex ParametersggDrained Friction Angle of Cohesive SoilsDrained Friction Angle of Cohesive Soils

20

20

40

40

50

60 80 100 200 400 600 100000

10

Soft Clays

Mexico CityClay

Attapulgite

Soft and Stiff ClaysShalesClay Minerials

30

Fric

ttion

Ang

le,

(d

egre

es)

Plasticity Index, I (%)p

’

Correlations of Shear Strength with Correlations of Shear Strength with Index ParametersIndex ParametersggFriction Angle of Friction Angle of CohesionlessCohesionless SoilsSoils

Correlations of Shear Strength with Correlations of Shear Strength with Index ParametersIndex ParametersggRelative Density in terms of NRelative Density in terms of N--valuevalue

PermeabilityPermeability

ggAlso known as “Hydraulic Conductivity”Also known as “Hydraulic Conductivity”ggFlow rate through Flow rate through geomaterialgeomaterialggSignificantly influences the selection of Significantly influences the selection of

backfill materialbackfill materialggHazen’s equationHazen’s equation

k = C(D10)2

PermeametersPermeameters

Rigid WallRigid Wall Flexible WallFlexible Wall

PermeabilityPermeability

ggGranular soilsGranular soils

PermeabilityPermeability

PermeabilityPermeability

ggPermeabilitiesPermeabilities of common highway materialsof common highway materials

Materials Permeability (m/s) Uniformly graded coarse aggregate 0.4 - 4x10-3 Well-graded aggregate without fines 4x10-3 - 4x10-5 Concrete sand, low dust content 7x10-4 - 7x10-6 Concrete sand, high dust content 7x10-6 - 7x10-8 Silty and clayey sands 10-7 - 10-9 Compacted silt 7x10-8 - 7x10-10 Compacted clay less than 10-9 Bituminous concrete (new pavements)* 4x10-5 - 4x10-8 Portland cement concrete less than 10-10 * Values as low as 10-10 have been reported for sealed, traffic compacted highway pavement.

Volume ChangeVolume Change

ggSwellSwell-- ClaysClays-- Under moisture ingressUnder moisture ingress

ggCollapseCollapse-- Silts and claysSilts and clays-- Under load and/or moisture ingressUnder load and/or moisture ingress

Swell PotentialSwell Potential

ggClaysClaysggMoisture Moisture

ingressingressggConsolidometerConsolidometerggCA, WY, CO, TXCA, WY, CO, TXggDamage to Damage to

slabs and wallsslabs and walls

Collapse PotentialCollapse Potential

gg Silts and claysSilts and claysgg ConsolidometerConsolidometergg Load, moistureLoad, moisturegg Full saturation is Full saturation is

not necessarynot necessarygg Southwest, Southwest,

MidwestMidwestgg Damage to slabs Damage to slabs

and facilitiesand facilities

Collapse PotentialCollapse Potential

gg% collapse per foot basis% collapse per foot basisgg1% of 1 ft is 0.12”1% of 1 ft is 0.12”

Collapse Potential (CP) Severity of Problem 0 None

0.1 to 2% Slight 2.1 to 6% Moderate 6.1 to 10% Moderately Severe

>10% Severe

CompactionCompaction

ggOne of the most important elements in One of the most important elements in construction of soil structuresconstruction of soil structures

ggDensifyingDensifying the structure of soil by the structure of soil by application of external energyapplication of external energy

ggMeasured in laboratory by applying impact Measured in laboratory by applying impact energy to samples at various moisture energy to samples at various moisture contentscontents-- Standard Proctor testStandard Proctor test-- Modified Proctor testModified Proctor test

ggTable 5Table 5--1313

Compaction Moisture Content, w (%)

Dry

uni

t wei

ght (

dens

ity), γ d

, pcf

(Mg/

m3 )

Gs = 2.7

Specification for Field CompactionSpecification for Field Compaction

ggDisconnect between laboratory and field Disconnect between laboratory and field compaction energycompaction energy-- Laboratory is impact energyLaboratory is impact energy-- Field compaction is commonly by static load, Field compaction is commonly by static load,

vibration and/or kneading, vibration and/or kneading, ggEndEnd--product specificationproduct specification

-- Relative compactionRelative compaction-- % dry density compared to laboratory values% dry density compared to laboratory values

Relative Compaction, RCRelative Compaction, RC

ggA specification might say “ Achieve dry A specification might say “ Achieve dry density equivalent to 90% of the standard density equivalent to 90% of the standard proctor maximum dry density with moisture proctor maximum dry density with moisture content within content within ±±2% of optimum moisture 2% of optimum moisture contentcontent

%100xRCmaxd

fielddγ

γ=

Relative Compaction and Relative Relative Compaction and Relative DensityDensityggRelative Compaction, RC applied to most Relative Compaction, RC applied to most

soilssoilsggRelative Density, DRelative Density, DRR, applies to granular soils , applies to granular soils

onlyonlyDDRR=0% =0% for RC=80%for RC=80%DDRR=100%=100% for RC=100%for RC=100%

ggEvery 1% increase in RC beyond 80% Every 1% increase in RC beyond 80% increases Dincreases DRR by 5%by 5%

Every 1% increase in RC beyond 80% Every 1% increase in RC beyond 80% increases Dincreases DRR by 5% …….. What does by 5% …….. What does this mean?this mean?ggExample for SW soilsExample for SW soilsggEvery 1% increase in RC beyond 80% Every 1% increase in RC beyond 80%

increases 3.3% increase in shear strengthincreases 3.3% increase in shear strengthggGoing from DGoing from DRR of 50% to 100% increases of 50% to 100% increases

shear strength by 33%shear strength by 33%ggDDRR of 50% is RC = 90% for Modified Proctorof 50% is RC = 90% for Modified ProctorggDDRR of 100% is RC = 100% for Modified Proctorof 100% is RC = 100% for Modified Proctor

Properties of Compacted SoilsProperties of Compacted Soils

ggTable 5Table 5--1515

ggEffect of saturation on properties of Effect of saturation on properties of compacted soilscompacted soils

Common Sense Guidelines for Common Sense Guidelines for Laboratory Testing of SoilsLaboratory Testing of SoilsggTable 5Table 5--1616

Laboratory Tests for RocksLaboratory Tests for Rocks

ggTable 5Table 5--18 18

ggCompressive StrengthCompressive StrengthggDirect shear (for rock joints)Direct shear (for rock joints)ggDurabilityDurabilityggStrengthStrength--deformationdeformation

Point Load Strength TestPoint Load Strength Test

ggCorrelations with Correlations with unaxialunaxial compressive compressive strength testsstrength tests

Direct Shear TestDirect Shear Test(for rock joints)(for rock joints)

Common Sense Guidelines for Common Sense Guidelines for Laboratory Testing of RocksLaboratory Testing of RocksggTable 5Table 5--1919

Elastic Properties of Soils and RocksElastic Properties of Soils and Rocks

ggFor soils, Table 5For soils, Table 5--20 and 520 and 5--2121

ggFor rocks, Table 5For rocks, Table 5--22 and 522 and 5--2323

Elastic Modulus of Rock MassElastic Modulus of Rock Mass

ggRock mass controls engineering behavior of Rock mass controls engineering behavior of rockrock

ggEstimate Estimate EEmm in terms Rock Mass Rating in terms Rock Mass Rating (RMR) (RMR)

ggSee Table 5See Table 5--24 for 24 for EEmm in terms Rock Quality in terms Rock Quality Designation (RQD)Designation (RQD)

Em= 145000 x [10 (RMR-10)/40] in psi

Practical Aspects of Laboratory Practical Aspects of Laboratory TestingTestingggPrivate laboratories must be properly Private laboratories must be properly

certifiedcertified-- AASHTO, ASTM, Local DOT certificationsAASHTO, ASTM, Local DOT certifications

ggSchedule and perform the tests when they Schedule and perform the tests when they can be of maximum use in the designcan be of maximum use in the design

Variability of Measured PropertiesVariability of Measured PropertiesMeasured or interpreted parameter value Coefficient of Variation, V

(%)

Unit weight, γ 3 to 7 %

Buoyant unit weight, γb 0 to 10 %

Effective stress friction angle, φ′ 2 to 13 % Undrained shear strength, su 13 to 40 %

Undrained strength ratio (su/po) 5 to 15 % Compression index, Cc 10 to 37 %

Preconsolidation pressure, pc 10 to 35 % Hydraulic conductivity of saturated clay, k 68 to 90 %

Hydraulic conductivity of partially-saturated clay, k 130 to 240 % Coefficient of consolidation, cv 33 to 68 %

Standard penetration blow count, N 15 to 45 % Electric cone penetration test, qc 5 to 15 %

Mechanical cone penetration test, qc 15 to 37 % Vane shear test undrained strength, suVST 10 to 20 %

Learning OutcomesLearning Outcomes

ggAt the end of this session, the participant will At the end of this session, the participant will be able to:be able to:-- Contrast index and performance laboratory testsContrast index and performance laboratory tests-- Recall types of index testsRecall types of index tests-- Identify types of soil performance testsIdentify types of soil performance tests-- Describe soil consolidation testDescribe soil consolidation test-- Compare soil strength testsCompare soil strength tests-- Discuss soil compaction proceduresDiscuss soil compaction procedures-- Restate types of rock testsRestate types of rock tests

Any Questions?Any Questions?

THE ROAD TOUNDERSTANDING

SOILSAND

FOUNDATIONS

Any Questions?Any Questions?

THE ROAD TOUNDERSTANDING

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.4Section A.4

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 settlement

Design soil profile Magnitude of settlement 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

Step 1: Construct Step 1: Construct ppoo DiagramDiagram

gg See Table A.4See Table A.4--1 for 1 for unit weightsunit weights

gg See Table A.4See Table A.4--2 for 2 for computations for computations for ppoodiagramdiagram

gg Using Using ppoo values values specify loads, test specify loads, test duration and loading duration and loading pattern for pattern for consolidation test and consolidation test and confining pressures confining pressures for UU testsfor UU tests

psf

600(3x110)

Step 2: Prepare Laboratory RequestStep 2: Prepare Laboratory Request

Step 3: Determine Design ParametersStep 3: Determine Design Parameters

ggDetermine consolidation parameters from Determine consolidation parameters from the consolidation test (pthe consolidation test (ppp, C, Ccc, C, Crr, , ccvv))

ggPlot the values of the Plot the values of the preconsolidationpreconsolidationpressure (ppressure (ppp) on ) on ppoo diagramdiagram

ggDetermine Determine undrainedundrained shear strength shear strength ssuu and and ccuu from UU and CU tests, respectivelyfrom UU and CU tests, respectively

ggPlot the results of vane shear test (V), UU Plot the results of vane shear test (V), UU tests (U) and CU tests (CU) versus depth in tests (U) and CU tests (CU) versus depth in the clay layerthe clay layer

Plot of Plot of PreconsolidationPreconsolidationPressure on Pressure on ppoodiagramdiagramggSince pSince pcc is is

greater than greater than ppoo, , the the siltysilty clay is clay is overconsolidatedoverconsolidated

Plot of Variation of Plot of Variation of UndrainedUndrained Shear Shear StrengthStrengthggV: Vane V: Vane

Shear TestShear TestggU: UU testU: UU testggC: CU testC: CU test

Any Questions?Any Questions?

THE ROAD TOUNDERSTANDING

SOILSAND

FOUNDATIONS