advance foundation engineering design principles.pdf
TRANSCRIPT
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ADVANCE FOUNDATIONADVANCE FOUNDATIONENGINEERINGENGINEERING
ASSOC. PROF. Ir. DR. RAMLIASSOC. PROF. Ir. DR. RAMLI NAZIRNAZIR
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SUCCESSFUL FOUNDATIONENGINEERING FAILURE
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Normally there are 3 stages of design i.eNormally there are 3 stages of design i.e
1.1. PRE DESIGN STAGEPRE DESIGN STAGE
2.2. CONSTRUCTION STAGECONSTRUCTION STAGE
3.3. POST DESIGN STAGEPOST DESIGN STAGE
Accurate and reliable SI data is vital.Accurate and reliable SI data is vital.
Type of foundation use for the structure is based from theType of foundation use for the structure is based from the
a ove.a ove.An overall aspect and anticipation during construction has to beAn overall aspect and anticipation during construction has to be
. .
During this stage, loading, foundation arrangement and location,During this stage, loading, foundation arrangement and location,. .
Anticipation of the problem in foundation construction workAnticipation of the problem in foundation construction workshould be reco nised and overcomin the roblem should beshould be reco nised and overcomin the roblem should be
readily available.readily available.
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Which one to use???Which one to use???
OTAL STRESS ANALYSISOTAL STRESS ANALYSIS
OrOr
EFFECTIVE STRESS ANALYSISEFFECTIVE STRESS ANALYSIS
This type of analysis uses the undrained shear strength of theThis type of analysis uses the undrained shear strength of thecohesive soil and also known as short term analysis.cohesive soil and also known as short term analysis.
e un ra ne s ear strengt , ce un ra ne s ear strengt , cuu can e o ta ne rom e succan e o ta ne rom e sucas vane shear and laboratory such as unconfined compressionas vane shear and laboratory such as unconfined compression..
depth then cdepth then cuu = c and= c and =0=0oo. The use of unconsolidated. The use of unconsolidated
undrained triaxial compression test is also applicable providedundrained triaxial compression test is also applicable providedthat it is saturated plastic soil.that it is saturated plastic soil.
The groundwater does not have an effect in the use of totalThe groundwater does not have an effect in the use of totalstress parameters.stress parameters.
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This type of analysis uses the drained shear strength, c andThis type of analysis uses the drained shear strength, c and of ofthe plastic soil.the plastic soil.
The drained shear strength could be obtained from triaxialThe drained shear strength could be obtained from triaxialcompress on test w t pore pressure measurement teste on acompress on test w t pore pressure measurement teste on afully saturated specimen of the plastic soil.fully saturated specimen of the plastic soil.
--water pressure (positive or negative) from the loading haswater pressure (positive or negative) from the loading hasdissi ated and the h drostatic ore ressure conditions nowdissi ated and the h drostatic ore ressure conditions nowprevail in the field.prevail in the field.
Thus the location of the water table is significant in consideringThus the location of the water table is significant in consideringin the analysis.in the analysis.
Governing Conditions (TSA and ESA)Governing Conditions (TSA and ESA)Total stress analysis will provide a lower allowable bearingTotal stress analysis will provide a lower allowable bearingcapacity for soft or very soft saturated plastic soils.capacity for soft or very soft saturated plastic soils.
s s ue o e oa rom oun a on a w conso a e es s ue o e oa rom oun a on a w conso a e eplastic soil leading to an increase in shear strength as time passes.plastic soil leading to an increase in shear strength as time passes.
For Effective stress anal sis the shear stren th is hi her for softFor Effective stress anal sis the shear stren th is hi her for soft
or very soft saturated plastic soils which will results in higheror very soft saturated plastic soils which will results in higherbearing capacity.bearing capacity.
Effective stress analysis will provide lower bearing capacity forEffective stress analysis will provide lower bearing capacity forvery stiff or hard saturated plastic soils.very stiff or hard saturated plastic soils.
deformation since the soil are usually heavily overconsolidated.deformation since the soil are usually heavily overconsolidated.
As the soil dilates it tends to develo ne ative ore ressure. AsAs the soil dilates it tends to develo ne ative ore ressure. As
these pressure dissipates with times the shear strength of thethese pressure dissipates with times the shear strength of theheavily overconsolidated plastic soil will decrease. This will lowerheavily overconsolidated plastic soil will decrease. This will lower. .
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Firm to stiff saturated lastic soils are intermediate conditions.Firm to stiff saturated lastic soils are intermediate conditions.
The OCR and the tendency of the saturated plastics soiltoThe OCR and the tendency of the saturated plastics soiltoconsolidate will determine whether the TSA or ESA provides theconsolidate will determine whether the TSA or ESA provides thelower bearing capacity.lower bearing capacity.
SITE INVESTIGATIONSITE INVESTIGATION
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AA processprocess ofof sitesite explorationexploration consistingconsisting ofof boring,boring, samplingsampling andand
testingtesting soso asas toto obtainobtain geotechnicalgeotechnical informationinformation forfor aa safe,safe,..
conditionsconditions..
InIn otherother wordswords thethe mainmain purposepurpose ofof sitesite investigationinvestigation isis toto
determinedetermine ithinithin racticalractical limitslimits thethe de thde th thicknessthickness extentextent andandcompositionscompositions ofof eacheach subsoilsubsoil stratum,stratum, thethe depthdepth andand typetype ofof rock,rock,thethe depthdepth andand compositioncomposition ofof groundground water,water, thethe strength,strength,compressibilitycompressibility andand hydraulichydraulic charactristicscharactristics ofof soilsoil stratastrata asasrequiredrequired byby geotechnicalgeotechnical engineersengineers..
To study the general suitability of the site for an engineeringTo study the general suitability of the site for an engineeringproject. (FEED Program)project. (FEED Program)-- FRONTIER EVALUATIONFRONTIER EVALUATION
..
, . , .
o e erm ne e poss e cu es a may e encoun ereo e erm ne e poss e cu es a may e encoun ereby a specific construction method.by a specific construction method.
To study the suitability of construction material (soil or rock).To study the suitability of construction material (soil or rock).
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..
This is a part of geotechnical processes.This is a part of geotechnical processes.
Lack of geotechnical processes will lead to a:Lack of geotechnical processes will lead to a:--
Failures where many case histories areFailures where many case histories areavailable.available.
Si nificant dela and increase in constructionSi nificant dela and increase in constructioncosts when the design has to be revised orcosts when the design has to be revised or
ammended.ammended.
project thus it only comprises from only 0.1% to 5% of theproject thus it only comprises from only 0.1% to 5% of theproject cost.project cost.
YOU HAVE TO PAY FOR THE S.IYOU HAVE TO PAY FOR THE S.I
WHETHER YOU LIKE IT OR NOT!!WHETHER YOU LIKE IT OR NOT!!
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FACTORS INFLUENCING SELECTION OFFACTORS INFLUENCING SELECTION OFSI METHODSSI METHODS
Geological nature of site.Geological nature of site.
Topographical Nature of the siteTopographical Nature of the site
Type of information requiredType of information required
Financial Constraint and Time Restriction.Financial Constraint and Time Restriction.
WORK PROCEDURE FOR SITEWORK PROCEDURE FOR SITEINVESTIGATIONINVESTIGATION
Desk study to collect all the relevant data and informationDesk study to collect all the relevant data and information
ReconnaissanceReconnaissance
Plannin ro ram after reviewin the above.Plannin ro ram after reviewin the above.
Ground exploration: Boring, sampling and testing.Ground exploration: Boring, sampling and testing.
Laboratory testingLaboratory testing
repara on o reporrepara on o repor
DesignDesign
Review during construction and monitoring.Review during construction and monitoring.
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Location Plan : Preferably in a scale of 1:60000Location Plan : Preferably in a scale of 1:60000
Site PlanSite Plan
Other details such as loading condition, preliminary SI reports ifOther details such as loading condition, preliminary SI reports ifany should be included.any should be included.
PLANNING OF SITE INVESTIGATIONPLANNING OF SITE INVESTIGATIONWORKSWORKS
Surface InvestigationsSurface Investigations
SiteSite inspectioninspection toto assessassess generalgeneral sitesite conditionconditionifif therethere isis anyany anticipatedanticipated problemsproblems thatthat mightmightarisearise duringduring thethe constructionconstruction laterlater onon..
UsuallUsuall thethe en ineeren ineer isis re uiredre uired toto ins ectins ect thethesitesite toto appreciateappreciate actualactual sitesite andand groundgroundroblemsroblems withwith articulararticular referencereference toto terrainterrain
vegetation,vegetation, swamps,swamps, waterwater runrun off,off,strati ra hicalstrati ra hical formationsformations wherewhere thethe areareexposedexposed..
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PLANNING SCOPE OF SITEPLANNING SCOPE OF SITEINVESTIGATIONINVESTIGATION
Select methods of SI base on rinci le and uidelines sti ulatedSelect methods of SI base on rinci le and uidelines sti ulatedin BS 5390.in BS 5390.
Important considerations are : terrain features and accessibility,Important considerations are : terrain features and accessibility,geological conditions, types of sample and test required.geological conditions, types of sample and test required.
Estimate cost and time required.Estimate cost and time required.
Determine the number, depth and spacing of boreholes or otherDetermine the number, depth and spacing of boreholes or otherfield tests including the location of test, procedures etc.field tests including the location of test, procedures etc.
Determine frequency and types of insitu testing and sampling inDetermine frequency and types of insitu testing and sampling ineach borehole.each borehole.
Determine extent of supervision on testing and boring.Determine extent of supervision on testing and boring.
Prepare list of special precautions for the site investigationPrepare list of special precautions for the site investigationsuperv sor at s te, any.superv sor at s te, any.
Prepare scheme of laboratory testing after analysis of borelogs.Prepare scheme of laboratory testing after analysis of borelogs.
ROLE OF SI IN GEOTECHNICAL ENGINEERING DESIGNROLE OF SI IN GEOTECHNICAL ENGINEERING DESIGN
ENGINEERING PROPERTIES
SI SOILPROPERTIES
BASIC & INDEX PROPERTIES
MASS PROPERTIES
TYPICAL & GENERALISEDSUBSOIL PROFILE &
INTERPRETATION
JUDGEMENT
CHARACTERIZATION
GEOLOGICAL FORMATIONS,MAN MADE FILL etc..
ENGINEERING GEOLOGYMODELLING
GROUND
SOIL & ROCK MECHANICS
EFFECTIVE STRESS THEORY
SEEPAGE THEORY
CODE OF PRACTICES:- FOUNDATION BS 8004ANCHORS BS8081
PREDICTION
BEHAVIOUR
STRESS DISTRIBUTION
LATERAL PRESSURE
BEARING CAPACITY
COMPRESSIBILITY
REINFORCED FILLS BS8006GEOGUIDES
DEFORMATION
DISPLACEMENT
ENGINEERING INSTRUMENTATION FOR
STABILITY
PERFORMANCE EARTH PRESSURE DISPLACEMENT(SURFACE & SUBSURFACE INTERNAL STRESSES
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JKR PROBEJKR PROBE
HAND AUGERING (HA)HAND AUGERING (HA)MOTORISED HAND BORING (MHB)MOTORISED HAND BORING (MHB)
DEEP BORING (DB)DEEP BORING (DB)
TRIAL PITS AND PLATE BEARING TESTTRIAL PITS AND PLATE BEARING TEST
DEEP SOUNDING (DS)DEEP SOUNDING (DS)
INSITU VANE SHEAR TEST (IVST)INSITU VANE SHEAR TEST (IVST)
STANDARD PENETRATION TEST (SPT)STANDARD PENETRATION TEST (SPT)PRESSUREMETER TESTPRESSUREMETER TEST
GROUND WATER INVESTIGATIONGROUND WATER INVESTIGATION
ROCK CORINGROCK CORING
Simple and cheap dynamic penetrometer test used to check theSimple and cheap dynamic penetrometer test used to check theconsistency of subsoil.consistency of subsoil.
eve op y n an a ways m sta en w t ac ntoseve op y n an a ways m sta en w t ac ntosProbe.Probe.
at a height of 280mm through free fall.at a height of 280mm through free fall.
penetration.penetration.
Maximum enetration is about 12m or 400 blows 300mmMaximum enetration is about 12m or 400 blows 300mm
whichever arrives first.whichever arrives first.The robe is unable to enetrate into medium stren th soil andThe robe is unable to enetrate into medium stren th soil andgravelly ground.gravelly ground.
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Human errors :Human errors :--
Applying force to hammer resulting in less blow counts.Applying force to hammer resulting in less blow counts.
Penetration depth not marked correctlyPenetration depth not marked correctly Wrong counting.Wrong counting.
Instrumental error :Instrumental error :--
Stopper blow lost of damageStopper blow lost of damage
Worn out threads on coupling and driving rods.Worn out threads on coupling and driving rods.
JKR probe result can be used for shallow footing designs if theJKR probe result can be used for shallow footing designs if theresu s are cons s en .resu s are cons s en .
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Simple boring by hand with periodic removal of soil samples.Simple boring by hand with periodic removal of soil samples.
Normally no casing is used.Normally no casing is used.Usually used in soft to stiff cohesive soils or sandy silty soilUsually used in soft to stiff cohesive soils or sandy silty soilabove water table.above water table.
ept s m te a out m an t e ameter o t e ore o e sept s m te a out m an t e ameter o t e ore o e sabout 100mm.about 100mm.
s very use u o ge e so samp e or so c ass ca ons very use u o ge e so samp e or so c ass ca ontests and ground water observation.tests and ground water observation.
,,collapse and boiling may be noted even for a short exposurecollapse and boiling may be noted even for a short exposure(indicating shallow foundation is not practical)(indicating shallow foundation is not practical)
Commonly called wash boring consists of tripod with block andCommonly called wash boring consists of tripod with block andtackle or motor driven winch.tackle or motor driven winch.
e ore o e s a vance y c opp ng w e tw st ng ro s ane ore o e s a vance y c opp ng w e tw st ng ro s anwashing with pumpwashing with pump--circulated water.circulated water.
,,those containing big boulders.those containing big boulders.
especially when deeper than 10m.especially when deeper than 10m.
Ado ted easil at locations where access is difficult.Ado ted easil at locations where access is difficult.
Normally casing is used and depth of boring is about 20m.Normally casing is used and depth of boring is about 20m.
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DEEP BORINGDEEP BORING
Also refer as rotary drilling.Also refer as rotary drilling.
Basic component including drilling machine, drilling rods, casing,Basic component including drilling machine, drilling rods, casing,bits and sampling tools.bits and sampling tools.
Basic field test sets are SPT sets, vane shear set, MenardBasic field test sets are SPT sets, vane shear set, Menard
pressuremeter, etc.pressuremeter, etc.Borehole is advance by power rotation of drilling bit andBorehole is advance by power rotation of drilling bit andremova o cutt ngs y t e c rcu at ng water.remova o cutt ngs y t e c rcu at ng water.
Drilled rod are presented by hydraulic pressure.Drilled rod are presented by hydraulic pressure.
enever roc an ou ers are encountere , su ta e amonenever roc an ou ers are encountere , su ta e amonbits or tungsten carbide bits are to be used.bits or tungsten carbide bits are to be used.
as ng nee e o e use an c ang ng n s ra a are n ca e yas ng nee e o e use an c ang ng n s ra a are n ca e y
changing in the rate of advancing of borehole action of drillingchanging in the rate of advancing of borehole action of drillingrods and visual examination of cuttin s in drillin fluid.rods and visual examination of cuttin s in drillin fluid.
This is the most expensive soil investigation method but yet aThis is the most expensive soil investigation method but yet acomprehensive type.comprehensive type.
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ROTARY WASH BORING
Depth is usually about 5m and the side of open cuts need to beDepth is usually about 5m and the side of open cuts need to bebraced.braced.
or easy v sua exam nat on o so strata n t e r naturaor easy v sua exam nat on o so strata n t e r naturaconditions.conditions.
and design pressure is high.and design pressure is high.
rocks above water table or cohesive soils containing considerablerocks above water table or cohesive soils containing considerableamount of boulders or cobbles.amount of boulders or cobbles.
It is also used to locate buried pipes and services.It is also used to locate buried pipes and services.
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Vertical plate bearing is usually carried out in trial pit toVertical plate bearing is usually carried out in trial pit todetermine the shear strength and deformation characteristics ofdetermine the shear strength and deformation characteristics ofsoil/rock beneath the loaded plate.soil/rock beneath the loaded plate.
Useful in weathered rock, highly fractured rock, hardcore fill orUseful in weathered rock, highly fractured rock, hardcore fill or
where other test procedure are difficult or impossible to apply.where other test procedure are difficult or impossible to apply.
Square and circular plate is used to load in order to obtain theSquare and circular plate is used to load in order to obtain theloadload--settlement curve.settlement curve.
influence is limited by virtue of limited plate size.influence is limited by virtue of limited plate size.
In absence of additional penetrometer tests like SPT and JKRIn absence of additional penetrometer tests like SPT and JKRProbes, the test can be misleading.Probes, the test can be misleading.
DEEP SOUNDINGDEEP SOUNDING
Refers to static dutch cone penetrometer.Refers to static dutch cone penetrometer.oo
the end area of 10cmthe end area of 10cm22..
Com arativel a fast economical and sim le method and verCom arativel a fast economical and sim le method and ver
useful in coastal alluvial and thick deposits of weak to moderatelyuseful in coastal alluvial and thick deposits of weak to moderatelystrong soils.strong soils.
Deep soundaing cannot penetrate very dense soils with gravel orDeep soundaing cannot penetrate very dense soils with gravel orsoft rocks.soft rocks.
It does not reveal soil types but by Schmertmann method it canIt does not reveal soil types but by Schmertmann method it cancorrelate the type of soils.correlate the type of soils.
In permeable soils, deep sounding results give drained conditionIn permeable soils, deep sounding results give drained conditionstrength while in clays, it measures undrained strength of thestrength while in clays, it measures undrained strength of the
..
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Cone ResistanceCone Resistance
CCkdkd(kg/cm(kg/cm22))
Relative DensityRelative Density
DDrr (%)(%)
Angle of InternalAngle of InternalFriction,Friction,
< 20< 20 < 20< 20 2525 -- 3030
2020 -- 4040 2020 -- 4040 3030 -- 3535
4040 -- 120120 4040 6060 3535 -- 4040
120120 -- 200200 6060 -- 8080 4040 -- 4545
--
== ==ss
ffss = C= Ckdkd/150/150 if Cif Ckdkd
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Used to determine the undrained cohesion of clay in fieldUsed to determine the undrained cohesion of clay in field
conditions which are generally difficult to simulate in the lab.conditions which are generally difficult to simulate in the lab.as ca y cons sts o t e our a e vane t at w penetrate ntoas ca y cons sts o t e our a e vane t at w penetrate nto
the undisturbed soil and rotated at a constant rate between 6the undisturbed soil and rotated at a constant rate between 6oo totooo ..
The results are reliable for saturated clayey soil without gravel orThe results are reliable for saturated clayey soil without gravel orcoarse sands.coarse sands.
For very soft to stiff clay (cFor very soft to stiff clay (cuu < 50kPa) the blade size should be< 50kPa) the blade size should be
75mm wide by 150mm long.75mm wide by 150mm long.For stronger soil (cFor stronger soil (cuu between 50 and 100 kPa) the blade sizebetween 50 and 100 kPa) the blade sizeshould be 50mm to 100mm long.should be 50mm to 100mm long.
This a dynamic field test usually carried out in boreholes.This a dynamic field test usually carried out in boreholes.
Test consists of driving a standard split barrel sampler 50.8mmTest consists of driving a standard split barrel sampler 50.8mmin diameter.in diameter.
The SPT is read from a 65kg drop hammer fall at a verticalThe SPT is read from a 65kg drop hammer fall at a verticale g o cm.e g o cm.
e samp er s r ven to a tota o cm nto t e so an t ee samp er s r ven to a tota o cm nto t e so an t e
number of blows recorded for the last 30cm of penetrationnumber of blows recorded for the last 30cm of penetration--,,
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,,
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STANDARD PENETRATION TEST VALUESTANDARD PENETRATION TEST VALUEFOR DESIGNFOR DESIGN
eve ope n an current y t e most popu ar met o an econom ca means to o ta neve ope n an current y t e most popu ar met o an econom ca means to o ta nsubsurface information.subsurface information.
Currently 85%Currently 85% -- 90% of usage in conventional foundation design.90% of usage in conventional foundation design.es cons s o :es cons s o :--
Driving the split barrel sample at a distance of 460mm into the soil at the bottom of boring.Driving the split barrel sample at a distance of 460mm into the soil at the bottom of boring.
Counting the number of blows to drive sample at last two 150mm distances to obtain NCounting the number of blows to drive sample at last two 150mm distances to obtain Nvaluevalue
Using 63.5kg driving mass falling free from a height of 760mm.Using 63.5kg driving mass falling free from a height of 760mm.
The boring log shows refusal and the test is halted if:The boring log shows refusal and the test is halted if:--
50 blows are required for any 150mm increment50 blows are required for any 150mm increment
100 blows are obtained to drive the required 300mm100 blows are obtained to drive the required 300mm
10 successive blows produce no advance.10 successive blows produce no advance.
When full test depth cannot be obtained, boring log will show aWhen full test depth cannot be obtained, boring log will show a
a penetration of 100mm.a penetration of 100mm.
The blow count is directl related to the drivin ener :The blow count is directl related to the drivin ener :--
W1
mv2
1E
2
2
gh2v
vg2
u s u ng o equa on:u s u ng o equa on:--
Wh
gh2g
W
2
1E
W= weight of mass or hammer
H = height of fall
For standard test:For standard test:--
E = 63.5 x 9.81 x 0.762E = 63.5 x 9.81 x 0.762
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ovac an a omone oun t at t e actua energy mpact to t e samp er range a out toovac an a omone oun t at t e actua energy mpact to t e samp er range a out to80% while Riggs (1983) obtained energy input from 70% to 100%80% while Riggs (1983) obtained energy input from 70% to 100%
The discrepancies arises from:The discrepancies arises from:--
Driving hammer configurationDriving hammer configuration
Usage of liner inside the barrelUsage of liner inside the barrel
Overburden ressureOverburden ressure
Length of drill rodLength of drill rod
Therefore SPT can be standardised to some energy ratio ETherefore SPT can be standardised to some energy ratio Err such that:such that:--
EErr= (Actual hammer energy to sampler (E= (Actual hammer energy to sampler (Eaa)/ Input Energy (E)) x 100)/ Input Energy (E)) x 100
Energy input of 70% is normally use since observation is close toEnergy input of 70% is normally use since observation is close tothe actual energy ratio (the actual energy ratio (EErr))
ere ore t e stan ar ow countere ore t e stan ar ow count 7070 s measure rom ass measure rom asfollows:follows:
NN7070 = C= CNN x N xx N x xx xx xx
WhereWhere ii = adjustment factor from table= adjustment factor from table
7070 = uste= uste
CCNN = Adjustment for effective overburden pressure= Adjustment for effective overburden pressure
'p
76.95C
o
N
po in kPa
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Note that largerNote that larger EErr decrease the blow count nearly linearlydecrease the blow count nearly linearly
i.ei.e EEr45r45 gives N=20gives N=20
EEr90r90 gives N = 10gives N = 10
==r70r70
Energy ratio x blow count should be constant thus :Energy ratio x blow count should be constant thus :-- 1r
22r11r
E
xNExNE
Say ESay Er1r1 = 70 thus gives N= 70 thus gives N22 = (70/E= (70/Er2r2)xN)xN11
1
2rE
Say NSay N22 for Efor Er45r45 = 20 = E= 20 = Er2r2We obtain NWe obtain N11 = 13= 13
If we convert NIf we convert N7070 to Nto N6060 than N2 = N60 = (70/60)x13 = 15than N2 = N60 = (70/60)x13 = 15
Using the equation we can readily convert any energy ratio to any other base.Using the equation we can readily convert any energy ratio to any other base.
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It can be used in correlation for unit weightIt can be used in correlation for unit weight relative density,relative density,
DDrr, angle of internal friction angle, angle of internal friction angle , undrained compressive, undrained compressive,, uu,, -- ..
Angle of internal friction:Angle of internal friction:--20N5.4 70
Relative DensityRelative Density o2r
70
'p288.032
D
'N
ase rom eyer o :ase rom eyer o :
where pwhere poo is in kPais in kPaoOCR
70 'BCA'N or empton suggest t e o ow ng a ustment asor empton suggest t e o ow ng a ustment asbeen made:been made:--
2
rD
Where A range between 15 to 54Where A range between 15 to 54
. . . .
AndAndonc
OCR
'pC
oOCR'p
For CFor COCROCR=1 it relates to normally consolidated clay=1 it relates to normally consolidated clayrD
o15
o28
Thus Meyerhof estimate:Thus Meyerhof estimate:--
A correlation for N versus qA correlation for N versus quu in general form of:in general form of:--
qquu = kN= kN
ere ten to e s te epen ant.ere ten to e s te epen ant.
However k = 12 has been used i.e for NHowever k = 12 has been used i.e for N7070 = 10, q= 10, quu = 120kPa= 120kPa
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--
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Relationship between Angle of Internal Friction and N-Value(Sandy Soil)
SPT (Standard Penetration Test)
Hammer TypeHammer TypeSPTSPT
N-SPT = Total No. o lows or s oon sam ler to enetrate at a
c (t/m2) = 2/3 N
depth of 30cm
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Relationship between Cohesion and N-Value (Cohesive soil)
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--
Current practise is to use an average N but in the zone ofCurrent practise is to use an average N but in the zone ofmajoring stress.majoring stress.
prea oun at onprea oun at on t e zone o nterest s rom a out tot e zone o nterest s rom a out to2B below the base of footing.2B below the base of footing.
iz.N
i
av
z
For pile foundations, there may be merit in the simple average ofFor pile foundations, there may be merit in the simple average of. .
It may be better to subdivide the thick stratum into several strataIt may be better to subdivide the thick stratum into several strata. .
Average corrected NAverage corrected N7070 can be computed and then average.can be computed and then average.
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Pile LocationPile Location Skin Resistance (kN)Skin Resistance (kN) End Bearing (kN)End Bearing (kN)
SandSand 3 N3 NavavAAss 400 N400 NbbAAbb
SiltSilt 2.5 N2.5 NavavAAss 300 N300 NbbAAbb
avav ss
Using MenardUsing Menard PressuremeterPressuremeter test to carry out in a borehole bytest to carry out in a borehole byapp y ng pressure.app y ng pressure.
ForFor undrainedundrained condition, the pressure is maintained for a minutecondition, the pressure is maintained for a minute..
The probe pressure, in applied step, is increasedThe probe pressure, in applied step, is increased untilluntill limitlimitressure Pressure P ..
--
== ==11 oo uu,,
ccuu = (P= (P11 PPoo)/10 + 2.5 (kg/cm)/10 + 2.5 (kg/cm22))
--
PP11 = P= PooNN22where N = tanwhere N = tan22(45 +(45 + /2)/2)
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GROUND WATER INVESTIGATIONGROUND WATER INVESTIGATION
Parameters of importance in groundwater investigation are:Parameters of importance in groundwater investigation are: Existence of water table; normal perched or artisan.Existence of water table; normal perched or artisan.
Exact GWT and lower limit ofExact GWT and lower limit of erhederhed round waterround water
Thickness of strata and theThickness of strata and the piezometricpiezometric level of artisan groundwater.level of artisan groundwater.
Variation of these characteristics over the site and with timeVariation of these characteristics over the site and with time . .
Precaution taken while collecting water samples:Precaution taken while collecting water samples:
. .
If possible collect the water before addition of water to borehole.If possible collect the water before addition of water to borehole.
Make sure the subsoil water is not contaminated by rain water or surface water.Make sure the subsoil water is not contaminated by rain water or surface water.
,,and then allowing to riseand then allowing to rise titi its original position and collect the water sample.its original position and collect the water sample.
Water sample shall be stored in airtight and clean container.Water sample shall be stored in airtight and clean container.
. .
To determine the soundness of rock.To determine the soundness of rock. SoundSound rockrock :: RockRock whichwhich ringring whenwhen struckstruck withwith aa pickpick oror barbar.. DoesDoes notnot integrateintegrate
afterafter exposureexposure toto airair oror water,water, breaksbreaks withwith aa sharp,sharp, freshfresh fracture,fracture, inin whichwhich
crackscracks areare unweatheredunweathered andand lessless thanthan 33mmmm widewide andand generallygenerally notnot closercloser thanthan11mm apartapart.. CoreCore recoveryrecovery isis normallynormally 8585%%..
Me iumMe ium rocroc :: C aracteristicC aracteristic asas oror sounsoun rocroc utut t et e crac scrac s may emay e 66mmmm wi ewi eandand slightlyslightly weathered,weathered, generallygenerally nono closercloser thanthan 6060cmcm.. CoreCore recoveryrecovery isis 5050%% orormoremore..
IntermediateIntermediate rockrock :: GiveGive dulldull soundsound whenwhen hithit byby pickpick oror barbar.. DoesDoes notnot integrateintegrateafterafter exposureexposure toto airair oror waterwater.. BrokenBroken piecespieces maymay showshow weatheredweathered facesfaces..FracturesFractures uu toto 2525mmmm widewide andand s aces ace nono closercloser thanthan 3030cmcm.. CoreCore recoverrecovergenerallygenerally isis 3535%% oror greatergreater..
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2 TYPES OF SAMPLE :2 TYPES OF SAMPLE :--
n s ur en s ur e :: oo e erm nee erm ne proper esproper es sucsuc asas s rengs reng parame ers,parame ers,consolidation,consolidation, permeabilitypermeability andand parametersparameters whichwhich needneed toto observedobserved asas perper sitesiteconditioncondition..
DisturbedDisturbed :: DoDo determinedetermine physicalphysical propertiesproperties suchsuch asas graingrain size,size, colourcolour,, texture,texture,compactioncompaction properties,properties, remouldedremoulded propertiesproperties andand forfor testingtesting etcetc..
Causes of samples disturbance :Causes of samples disturbance :--
From boring processesFrom boring processes
Driving the sampling toolsDriving the sampling tools
Withdraw of sampling toolsWithdraw of sampling tools
The relief of stresses in the soilThe relief of stresses in the soil
Methods to reduce disturbance :Methods to reduce disturbance :--
B fixin extension ieces at each end of the sam lin tube.B fixin extension ieces at each end of the sam lin tube.
For soft sensitive soil use piston samplerFor soft sensitive soil use piston sampler
Sealed sample to reduce moisture losses.Sealed sample to reduce moisture losses.
Sample identificationSample identification..
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TheThe amountamount ofof samplesample disturbancedisturbance dependsdepends onon severalseveral factorsfactors asas
followsfollows::-- ape o cu ng e geape o cu ng e ge
Area of container relative to area of soil.Area of container relative to area of soil.
AArr =( D=( Doo22 DDii
22 ) / D) / Dii22 Ar < 0.01Ar < 0.01
..recoverrecover lengthlength andand makemake itit lessless thanthan pushpush lengthlength..
A measure of disturbance is called a recovery ratioA measure of disturbance is called a recovery ratio
LLrr = Length Recovered / Length Pushed= Length Recovered / Length Pushed
LLrr < 1.0< 1.0 -- soil in compressionsoil in compression
LLrr > 1.0> 1.0 -- soil in expansionsoil in expansion
If LIf Lrr not equal to 1.0not equal to 1.0 -- sample are disturbedsample are disturbed
Soil character itself. If the soil is highly sensitive, insitu testingSoil character itself. If the soil is highly sensitive, insitu testingill be dominant.ill be dominant.
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FIELD IDENTIFICATION ANDFIELD IDENTIFICATION ANDDESCRIPTION OF SOILDESCRIPTION OF SOIL
Soil descriptions are made from washed and disturbed samplesSoil descriptions are made from washed and disturbed samples
recovered from the boreholes.recovered from the boreholes.
The soil name is based on particle size distribution and plasticity,The soil name is based on particle size distribution and plasticity,. .
According to BS 5930, soil samples are described with each element ofAccording to BS 5930, soil samples are described with each element ofthe descriptions having a fixed position within the overall description:the descriptions having a fixed position within the overall description:-- a)a) Consistency (cohesive) or RD (non cohesive)Consistency (cohesive) or RD (non cohesive)
bb Fabric and Fissurin if distin uishableFabric and Fissurin if distin uishable
c)c) ColourColour
d)d) Subsidiary constituentSubsidiary constituent
ee An ularit or radin of rinci al soil t e for coarse rained soilAn ularit or radin of rinci al soil t e for coarse rained soil
f)f) Principal soil type (in capital letter)Principal soil type (in capital letter)
g)g) More detailed comments on constituents or fabric.More detailed comments on constituents or fabric.
EG.EG.
Dense (a) Brown (c)Dense (a) Brown (c) Fine to Coarse (e)Fine to Coarse (e) Angular (e) GRAVEL (f)Angular (e) GRAVEL (f)
Very Stiff (a) Greenish blue (c) Sandy (d) CLAY (f) With some rounded gravel (g)Very Stiff (a) Greenish blue (c) Sandy (d) CLAY (f) With some rounded gravel (g)
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When soils areWhen soils are desribeddesribed at field, it is important to learn how toat field, it is important to learn how tos ngu s e ween c ay an non co es ve so s on e as s os ngu s e ween c ay an non co es ve so s on e as s o
estimated engineeringestimated engineering behaviourbehaviour. (10% of clay can impart an. (10% of clay can impart anessentiall cohesiveessentiall cohesive behaviourbehaviour.. EE ..
A soil containing 50% of silt, 30% of clay and 20% of sand is described asA soil containing 50% of silt, 30% of clay and 20% of sand is described assandysandy siltysilty CLAY because the soil behaves more like a clay.CLAY because the soil behaves more like a clay.
Clayey SANDClayey SAND not cohesive, but contains claynot cohesive, but contains clay
Very clayey SAND or Very sandy CLAYVery clayey SAND or Very sandy CLAY borderlineborderline
Sandy CLAYSandy CLAY cohesive, but sand may be the major constituents by weight.cohesive, but sand may be the major constituents by weight.
The following description should be used when giving moreThe following description should be used when giving moredetailed comments on constituents of soils :detailed comments on constituents of soils :--
escr p onescr p on y w . o o a soy w . o o a so
.with traces of .with traces of 1010
.with a little of .with a little of 1010 -- 2020
.with some ...with some .. 2020 -- 3535
.and..and. 3535 -- 5050
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Site investigation. Describe what is needed in light of existing information, provide specific rationale for thescope and methods of site investigation to make it possible for reviewers to assess the adequacy of theinvestigation. Describe what was carried out. Show location of test holes or pits or geophysical lines if any.Include field observations at the site, soils and existing conditions.
. .
Evaluation and analysis. Discussion of the site investigation and laboratory test results and their implicationson the ro osed facilit or the stabilit of the site investi ated. The seismic assessment should be rovided.Describe analyses performed, assumptions, parameters and methods used (use two methods for analyzingslope stability or calculating bearing capacities where practical). Provide foundation or slope designinformation in terms of both static and dynamic (seismic) design if required and state what safety factors arein lace. Provide antici ated ran e of settlement for foundations and fills and FOS of fill. A l our fieldobservation of the site conditions and existing foundations if any, on your choice of foundation type.
Sand and Gravel Sources/ Disposal Areas. Provide legal description, status (Crown, lease, etc.). Describepotent a san an grave sources, teste or est mate mater a propert es an pro ecte quant t es. escr einvestigation methodology. Provide recommendations on waste or surplus material disposal areas.
, .
Point out possible foundation and construction difficulties, effects on the existing,
the preferred type of foundation, describe why and suggest possible alternatives(value engineering) where possible. Refer to findings of field investigation, lab test
.
given appropriate opportunity to review the geotechnical aspects of the completeddesign prior to construction.
Discuss predicted effects of the recommended work on the environment(water quality, etc.). Provide recommendations on mitigation measures.
Provide specifications and special provisions for construction contract. Provide costestimates for the recommended work.
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Literature References
Provide a list of references used in the preparation of the report.
Correspondence Soils & rock core logs (make sure standard disclaimers are, ,
for new roads, pit development plan, drawings, plan & profile, photos.
Reports must be signed and stamped both by the author and the reviewer. It is theres onsibilit of the author and the reviewer to determine the a ro riateness andaccuracy of input data and the correctness of the computed results. Use of computer programs does not free the Professional Engineer or the Professional
Geoscientist from this res onsibilit .
Surface InvestigationSurface Investigation
Site inspection of existing earth structure, slabs and foundation nearby.Site inspection of existing earth structure, slabs and foundation nearby.
Study Topographical, geological, hydrological map, data. Etc.Study Topographical, geological, hydrological map, data. Etc.
, . , .
Sub surface InvestigationSub surface Investigation
Test PitsTest Pits
Sam lin and Lab TestSam lin and Lab Test
LogLog
InsituInsitu TestingTesting
or ng esor ng es
Rotary boringRotary boring
Percussion boringPercussion boring
LogLog
Lab TestLab Test
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Sounding TestsSounding Tests
JKR ProbingJKR Probing
Dutch ConeDutch Cone PenetrometerPenetrometer
HandHand AugeringAugering
LogLog SamplingSampling
Lab TestLab Test
ScopeScope ofof sitesite investigationinvestigation worksworks whenwhen plannedplanned byby differentdifferent engineersengineers tendtend toto bebe variedvaried becausebecausetherethere areare anan infiniteinfinite numbernumber ofof conditionsconditions toto bebe metmet andand thethe processprocess ofof planningplanning alsoalso leavesleaves manymanyareasareas wherewhere individualindividual judgementjudgement andand experiencesexperiences mustmust bebe appliedapplied..
ItIt isis alsoalso impossibleimpossible toto attemptattempt toto provideprovide anan exhaustiveexhaustive stepstep byby stepstep guidelinesguidelines applicableapplicable toto allallpossiblepossible casescases..
It should be realised that there is a possibility that any siteIt should be realised that there is a possibility that any siteinvestigation may leave some area unexplored or overlooked.investigation may leave some area unexplored or overlooked.
The main risk in foundation design is the uncertainty involvingThe main risk in foundation design is the uncertainty involvingin predicting soil conditions which may change within predicting soil conditions which may change with
env ronment.env ronment.
More site investigation will reduce the margin of uncertainty butMore site investigation will reduce the margin of uncertainty butthe time and cost requirement will be exorbitant.the time and cost requirement will be exorbitant.
Therefore the extent and the cost of SI should be such that riskTherefore the extent and the cost of SI should be such that risk
comply to the accepted code of practise.comply to the accepted code of practise.
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Engineers should allow or apt with changes during constructionEngineers should allow or apt with changes during construction
of foundation at site.of foundation at site.ternat ve es gn nee to e n an w enever t ere areternat ve es gn nee to e n an w enever t ere are
changes during this stage.changes during this stage.
,,as the delay in making decision will hold or retarding the processas the delay in making decision will hold or retarding the processof construction.of construction.
This is a stage where foundation engineers are really tested inThis is a stage where foundation engineers are really tested in
their knowledge integrity.their knowledge integrity.This is also a stage where reliability of SI data is known.This is also a stage where reliability of SI data is known.
To validate the design, load test need to be carried out. TheTo validate the design, load test need to be carried out. Thedesigner may choose to have them conducted either before ordesigner may choose to have them conducted either before or
. .
The first alternative permits development or revision of designThe first alternative permits development or revision of design. .
The second saves expenses on mobilisation but may lead to delayThe second saves expenses on mobilisation but may lead to delayif the results is unsatisfactoril .if the results is unsatisfactoril .
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To ensure the pile workability before and after construction. It isTo ensure the pile workability before and after construction. It isalso as a method to determine settlement and ensuring that italso as a method to determine settlement and ensuring that itdoes not exceed allowable limit.does not exceed allowable limit.
Failure of load test according to JKR specification:Failure of load test according to JKR specification:--
1.1. Residual settlement at design load exceed 6.5mmResidual settlement at design load exceed 6.5mm
2.2. Total settlement at design load exceed 12.5mmTotal settlement at design load exceed 12.5mm
3.3. Total settlement exceed 38mm or 10% of pile diameter or widthTotal settlement exceed 38mm or 10% of pile diameter or widthwhichever is lower under twice design load.whichever is lower under twice design load.
et o s o statement s a e re er to pec cat on oret o s o statement s a e re er to pec cat on or
BS8004.BS8004.
arrangement have been made.arrangement have been made.
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The time lapse is sufficient for excess pore water pressure toThe time lapse is sufficient for excess pore water pressure toss pa es.ss pa es.
Pile in cohesive soils should be tested after sufficient lapse forPile in cohesive soils should be tested after sufficient lapse for. .
This time lapse is commonly in the order of 30 to 90 days givingThis time lapse is commonly in the order of 30 to 90 days giving. .
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LOAD
mm
mm
6.
12.
ment
DL
38mm
settl
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From point O to a the capacity is based on the skin resistance plus any small point contribution.From point O to a the capacity is based on the skin resistance plus any small point contribution.
From oint a to b the load ca acit is the sum of the limitin skin resistance lus the ointFrom oint a to b the load ca acit is the sum of the limitin skin resistance lus the oint
capacity.capacity.
From point b the curves becomes vertical as the ultimate point capacity is reached. Often the verticalFrom point b the curves becomes vertical as the ultimate point capacity is reached. Often the vertical
asymptote is anticipated and the test terminated before a vertical curve branch is established.asymptote is anticipated and the test terminated before a vertical curve branch is established.
250N
1600-250 = 1350 N
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STARTING POINT OF FOUNDATIONSTARTING POINT OF FOUNDATIONDESIGNDESIGN
Following steps are the minimum requirement for designing aFollowing steps are the minimum requirement for designing a
foundation.foundation.1.1. ocate t e s te an t e pos t on o t e oaocate t e s te an t e pos t on o t e oa
2.2. Physical inspect the site for any geological or other evidencePhysical inspect the site for any geological or other evidence
3.3. Establish the field exploration program for design parametersEstablish the field exploration program for design parameters
4.4. e erm ne necessary es gn parame ers ase on n egra on oe erm ne necessary es gn parame ers ase on n egra on otest data, scientific principles and engineering judgement.test data, scientific principles and engineering judgement.
.. economical and be able to be built by the available constructioneconomical and be able to be built by the available constructionpersonnel.personnel.
TWO MOST IMPORTANT QUESTION FOR DESIGNER!!!TWO MOST IMPORTANT QUESTION FOR DESIGNER!!!
WHAT LOADS ARE TO BE SUPPORTED.WHAT LOADS ARE TO BE SUPPORTED.
HOW FAR MAY THE FOUNDATION SETTLE INHOW FAR MAY THE FOUNDATION SETTLE INRESPONSE TO THESE LOAD.RESPONSE TO THESE LOAD.
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Generally the proper design requires the following:Generally the proper design requires the following:--
1.1. Determine the building purpose, probable service lifeDetermine the building purpose, probable service lifeoa ng, type o ram ng, so pro e, construct on met o soa ng, type o ram ng, so pro e, construct on met o sand construction cost.and construction cost.
.. . .
3.3. Making the design, but ensuring that it does not successivelyMaking the design, but ensuring that it does not successively
that produces a tolerable risk level to all parties, the public,that produces a tolerable risk level to all parties, the public,
the owner and the engineer.the owner and the engineer.
ADDITIONAL CONSIDERATION INADDITIONAL CONSIDERATION INFOUNDATION DESIGNFOUNDATION DESIGN
Adequate depthAdequate depth
Depth of foundation to be below seasonal changeDepth of foundation to be below seasonal change
Considering problematic soilConsidering problematic soilCompressive strength considerationCompressive strength consideration
Protection of foundation against natural causesProtection of foundation against natural causes
Sustainable to changesSustainable to changes
Buildable or limitation.Buildable or limitation.
Apt to local environment standard.Apt to local environment standard.
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Based from Neoh C.A, the choice of the foundation designs areBased from Neoh C.A, the choice of the foundation designs are
considered from:considered from:1.1. oa s per co umnoa s per co umn
2.2. Bearing type either end or skinBearing type either end or skin
3.3. ear ng ayerear ng ayer
4.4. Type of Intermediate layerType of Intermediate layer
5.5. Location of water level.Location of water level.
Assess Foundation BasePROCEDURE FOR THECHOICE OF FOUNDATIONTYPE FOR A SITE
Assess GrounConditions and Type ofStructures
YESAre pilenecessary
ChooseShallowFoundation
TechnicalConsiderationsfor Different Pile
Types:-
1. Ground Condition
2. Loading Assess construction programme for each
3. EnvironmentalConsiderations
4. Site and PlantConsiderations
on program consideration
Make overall rankin of each ile t e5. Safety
List all technically feasible pile types
based on technical, cost andprogramme considerations
an ran em n or er o su a ybased on technical consideration.
Submit individual and overall rankings of each piletype to client and make recommendation on most
suitable pile type.
rank them based on cost consideration.
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