Piezocone and Cone Penetration Test (CPTu and CPT) Applications in Foundation Engineering

376 Pages·2019·12.064 MB·English

by  Abolfazl Eslami

Piezocone and Cone
Penetration Test (CPTu and
CPT) Applications in
Foundation Engineering
Abolfazl Eslami
Professor
Dept. of Civil and Environmental Engineering
Amirkabir University of Technology (AUT)
Sara Moshfeghi
M.Sc. Graduate
Dept. of Civil and Environmental Engineering
Amirkabir University of Technology (AUT)
Hossein MolaAbasi
Assistant Professor
Dept. of Civil Engineering
Gonbad Kavous University
Mohammad M. Eslami
Ph.D. GeoPentech Inc.
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Preface
Geotechnicalinvestigationistheprocedureofacquiringinformationanddataonsub-
surfacesoilconditionsandsynthesizingtheminordertodeterminegeomaterialparam-
eters required for design. Despite notable progress, many solutions are still
approximate, which is mainly due to the natural inherent inhomogeneity of soils
and dominant environmental and geologic conditions. Among different sources of
dataproductionsavailabletoovercometheuncertaintiesandguidedengineeringjudg-
mentforinterpretations,in-situpenetrationtestsareemployedasacomplementaryand
versatiletooltolaboratorytestingandareconsideredtobefast,accurate,andeconom-
ical sources for collecting data.
In light of cost saving for geotechnical investigations and considering the time-
consumingprocessofconventionalproceduressuchasdrilling,sampling,transferring
samples,andlaboratorytesting,itismorefavoredtotakethemeasurementequipment
to the attributed project site. In addition, development of more equipped in-situ tests
has facilitated more comprehensive data compilations and proper understanding of
soil behavior. In-situ tests can be employed for directly defining soil profiling and
geotechnical soil parameters and characteristics.
Accordingly, in the realm of foundation engineering, due to the variety of condi-
tionsandparametersaffectingsoilbehavior,theanalysisanddesignoffoundationsys-
temsfordeterminingbearingcapacity,settlementestimation,andstabilitycontrolare
knowledge-basedandsophisticated.Inthisregard,theversatileconepenetrationtest,
CPT,orpiezocone,CPTu,providesvaluabledatacombiningtipresistance(q ),sleeve
c
friction(f)andexcessporepressure(u),andafewothersupplementaryrecords.Rep-
s
resentationofmostsoilin-situcharacteristicscanplayanimportantroletoselectand
interpret variousrequiredparameters for Performance-BasedDesign.
Moreover, the reliability of any foundation system design depends heavily on the
trustworthinessofinputvaluesofsoilpropertiesintheanalyses,whichinturndepends
onthelevelofaccuracyandcarefulnessofthesiteinvestigationandcharacterization
carriedout.Inthisregard,aninitialstepfortheengineeringprocessisthedevelopment
ofasubsurfaceprofileofsoiltypesandtheirgeotechnicalproperties,inwhichthecone
penetrationtest(CPT)isanidealtool.CPTsuppliescontinuousrecordswithdepthand
allowsavarietyofsensorstobeaccompaniedandisperformedunderfieldstressesand
boundaryconditions,actualconditionsthatthefoundationsystemwillencounterdur-
ingitsconstructionandlifetimefunctioning.Thechoiceofpileinstallationmethodas
well as pile material type is influenced by subsurface conditions, structural and
x Preface
geometrical characteristics of the project, in which the practical and economical
aspects areessential.
Among commonly used approaches for estimating the bearing capacity of deep
foundations,suchastheoreticalsolutions,staticanalysis,andfull-scaleloadingtests,
employment of in-situ records is realized as a supplementary of static analysis.
Evaluating the bearing capacity of foundations from CPT data is one of the earliest
applicationsofthistestandincludestwomainapproaches;directandindirectmethods.
DirectCPTmethodsapplythemeasuredvaluesofconebearingforbearingresistance
withsomemodificationsregardingscaleeffects,i.e.,theinfluenceoffoundationwidth
totheconediameterratio.IndirectCPTmethodsemployfrictionangleandundrained
shear strength values estimated from CPT data based on bearing capacity or cavity
expansion theories.
DuetosimilaritiesbetweenCPTandpile,conepenetrometerdatacanbeemployed
forthedeterminationofpilecapacitybyapplyingcorrectionsrelatedtogeometrydif-
ferencesandlimiteddisplacementofpileunderloadbearing.Theattemptstopredict
piletoeandshaftcapacitiesfromCPTdataweregenerallysuccessful.However,there
isstillsomeskepticismregardingtheapplicationofasmall-scaleconepenetrometerto
large-scalefoundations,whichisreferencedtoasscaleeffects.Regardingtheseissues
and in view of the scale effect to relate cone penetrometer to foundations, either
shallowordeep,criticalfactorshavebeeninvestigatedthroughexperimentalandtheo-
reticalapproaches.Forbothtoeandshaftcapacitydetermination,thefocusismainly
ondiameter,embedmentdepth,penetrationrate,strainlevel,homogeneitycondition,
influence zone, data processing, and ultimate pile capacityinterpretation.
ForachievingsuitableapplicationofCPTandCPTurecordsforsafeandoptimum
foundationdesignandfocusingonreliabilityapproaches,thematerialsofthisbookare
organized inthe followingfour major parts:
I FundamentalsofGeotechnicalandFoundationEngineeringviaIn-situTesting
II CPTandCPTu;Correlations,SBC,andScaleEffecttoFoundations
III CPTandCPTuImplementationinGeotechnicalDesignofFoundations
IV CPT-basedsoftcomputing,reliabilityanddata-baseddesignapproaches
In the first part, an initial introduction to geotechnical engineering has been pre-
sented in Chapter 1 including procedures and common sources of data acquisition.
Chapter 2 presents principles of Foundation Engineering, types and classifications,
in addition to major aspects for analysis and design. Additionally, uncertainties in
foundation engineering are recognized, and the role of CPT and CPTu data for a
morereliabledesignispresented.Chapter3dealswithintroducingtheConePenetra-
tion Test, detailed discussions about the apparatus, testing procedures, performance,
and data presentations.
InthesecondpartstartingwithChapter4,avarietyofcorrelationsarecoveredfor
estimating soil properties such as strength and stiffness parameters, particularly
employed in foundation engineering by means of CPT measurements. In Chapter 5,
the classification of soils by in-situ tests is demonstrated vastly. Then, various soil
behavior classification (SBC) charts and approaches in terms of CPT measurements,
especiallyforchallengingdeposits,arereviewedandcompared.Inaddition,torelate
Preface xi
penetrometertofoundation,Chapter6startswithintroducingfactorspertinenttoscale
effects. Then, it describes the application of CPT in geotechnical design of shallow
foundations in terms ofbearing capacity.
Forthethirdpart,Chapter7discussesdeepfoundationdata-baseddesign,andreal-
izingconepenetrometerasamodelpiledealswithawiderangeofdirectCPT-based
methodsinestimatingthepileaxialbearingcapacity.Additionally,itprovidesexam-
plesofdirectaswellasin-directimplementationofCPTrecordsincalculationofpile
bearing capacity. Chapter 8 encompasses various approaches for estimating founda-
tion settlement by CPT-based correlations and load-displacement behavior using
CPT records. Chapter 9 introduces challenging soils commonly encountered in
geotechnical practice and provides criteria for recognizing and classifying these soil
types by means of CPT and CPTu charts. Furthermore, this chapter introduces
applicationsofCPTforevaluatingandcomparingthesoilpropertiesbeforeandafter
soilimprovementasanindicatorofimprovementeffectiveness.Thecomparisonsare
presented intheform ofvariouscasestudies worldwide.
In the last part, Chapter 10 introduces the applicability of soft computing
techniques, such as the Group Method of Data Handling (GMDH)-type Neural
Network(NN),basedonCPTrecordsforpredictingpilebearingcapacityandshallow
foundation settlement. Chapter 11 deals with the topic of sources of uncertainty in
geotechnical engineering, and reliability-based approaches are introduced. Some
examples are presented on implementing reliability-based approaches in evaluating
theperformanceofCPT-basedmethodsofestimatingpilesbearingcapacity.Finally,
Chapter 12 demonstrates a wide range of CPT databases in the literature and their
applications. At the end, an extensive recently developed database is presented,
including records of CPT and CPTu piling records along with geotechnical
information.
Typical examples, explanations, applications, and implementation for enhancing
foundation geotechnical design via predictive methods, particularly for deep founda-
tions,areillustratedandinterpretedthroughafewsophisticateddatabanksincluding
foundationloading test records and nearby performed CPTor CPTu data.
Acknowledgment
Iwouldliketoexpressmysincerest gratitudetowardProfessorsBengtFelleniusand
Dick Campanella for various technical discussions and insights on CPT and Deep
Foundation Design, as well as nontechnical talks, mentorship, and their guidance
overthepast25yearsbeginninginOttawa,ON,andlaterinVancouver,BC,Canada
during and after my PhD studies. Additionally, I gratefully acknowledge Dr. J.A.
Infante, my fellow at the University of Ottawa, Civil Engineering Department, for
cooperation and development of the UniCone software (Eslami-Fellenius method),
used and employed for pile geotechnical design, presented in the early stages of this
millennium.
Partsofthisworkwereinitiallydevelopedintheenvironmentofthecivilengineer-
inggroupatAmirkabirUniversityofTechnology(AUT)andGuilanUniversity.Iam
grateful to many colleagues and counterparts in the geotechnical engineering groups
for their collaboration, discussions, and comments on various technical sections of
the chapters, and generally over the years. Additionally, I would like to thank
Amirkabir University of Technology IT group for assisting in creating the AUT:
Geo-CPT&Pile database, including more than 600 case records for piles and CPT,
accessible for worldwide usage.
Writing a textbook involves significant time commitment, which could only be
accomplished with the collective effort of my colleagues and students. With the
help of numerous graduate and undergraduate students at Guilan University and
AUT, extensive research has been carried out over the years on the contents of this
book; CPT, CPTu, and Foundations. This text, to a high degree, is a compilation of
theeffortsofmyformerandcurrentstudents,andtheirworkisgreatlyacknowledged.
I wish to present my special thanks to Dr. Sara Heidarie Golafzani for invaluable
contribution to contents of Chapter 11, Dr. Fatemeh Valikhah for precious aid in
Chapters 8 and 9, Mr. Mohammad Esmaeilzadeh for sharing data in Chapter 4, and
Mr.RaminEzzatdoustforpricelesstimeandeffortonpreparingthegraphicalcontents
of thechapters.
Iwouldliketoexpressmygratitudetowardmycoauthorsinthisbook,startingas
beingdedicatedstudentsinmyclassrooms,andnowexpertsinthefieldwhomI’vehad
the opportunity to work alongside in preparation of the book chapters and many
technical projects over the recent years. Ms. Sara Moshfeghi, for her continuous
specialized effort and organization of all chapter materials; Dr. Hossein MolaAbasi,
forinitiatingthisprojectanddevelopingthesoftcomputingsections;andDr.Mandro
xiv Acknowledgment
M. Eslami, for providing critical comments, constructive points, and expert peer
review.
I extend my most profound gratitude toward other authors and publishers who
contributed and provided many tables, charts, plots, and their underlying data and
permissionforreuseinthebookchapters.Withouttheircooperation,thisworkwould
nothavebeenpossible.Finally,IwouldliketothanktheElsevierpublishingteamfor
continuous assistanceand collaboration ineach step of preparingthis book.
ItishopedthatthisbookonCPTandCPTuapplicationsinFoundationEngineering
will serve its intended purpose and, hence, prove useful to readers as a resource in
understanding and addressing problems in teaching, research, and engineering
practice.
Abolfazl Eslami
October 2019
1
Geotechnical engineering
1.1 Introduction
Geotechnical engineering is the systematic application of techniques which allows
construction on, in, or with geomaterials, i.e., soil and rock. Every civil engineering
structureandconstructionisrelatedtosoilinsomeway,andsubsequently,itsdesign
will depend on properties of the soil or rock. Geotechnical operations are of impor-
tancewithrespecttosoilsampling,investigatinggeomaterialsproperties,controlling
groundwater level and flow as well as environmental and hydrological interactions.
Foundation engineering, excavations and supporting ground structures, underground
structures, dams, natural or artificial fills, roads and airports, subgrades and ground
structures, and slope stability assessments are examples of geotechnical engineering
applications inpractice.
Despite notable progress in geotechnical engineering, many solutions are still
approximate, which is mainly due to the natural inherent inhomogeneity of soils
anddominantenvironmentalconditions.Additionally,soilsaremoresensitivetolocal
environmental conditions compared to other prefabricated building materials such as
steelorconcrete.Consequently,itwouldbenecessarytohavecomprehensiveunder-
standingofnaturalsoildeposits,environmentinteractions,andresponsetolocalcon-
ditionstoallowmoreaccuratepredictionofgeomaterialsengineeringperformanceand
behavior inprojects.
Fig.1.1demonstratesseveralbranchesrelatedtogeotechnicalengineeringandtheir
overlap.Geotechnicalengineeringactivitiesareapartofateameffortinvolvingother
disciplines including geology, structural engineering, construction management, hy-
draulics, earthquake and transportation engineers, and other pertinent branches. The
final designof any project reflects a collaboration ofthese professions.
1.2 Topics in geotechnical engineering
Importance,application,andserviceabilityofstructures,alongwithbroadapplication
of natural geomaterials in construction projects, necessitate investigation, reconnais-
sance, collection as well as measurements of geomaterial properties reported inliter-
ature, laboratory, and field. This has led to the development of the branch of
“geotechnical exploration” or “geotechnical site investigation” in geotechnical
engineering.
The following themes areaddressed ingeotechnical engineering:
1. Characterizinganddefiningthelocationandthicknessofsubsurfacesoilandrockstrata
PiezoconeandConePenetrationTest(CPTuandCPT)ApplicationsinFoundationEngineering
https://doi.org/10.1016/B978-0-08-102766-0.00001-8
Copyright©2020ElsevierLtd.Allrightsreserved.
2 PiezoconeandConePenetrationTest(CPTuandCPT)ApplicationsinFoundationEngineering
Figure1.1 Overlapofgeotechnicalengineeringwithothersciences.
2. Samplerecoveryforobservation,testing,andevaluation
3. Determininggroundwaterconditionsandconsequencesofpossiblevariationsforprojectsin
future
4. Sufficiencyofsubsurfacegeomaterialsforsafebearingofsuperstructureloads
5. Consequencesandcomplicationscausedbyconstruction,earthworks,orexcavation
6. Selectinganddesignofappropriatefoundationsystemsforagivenproject
7. Considerations and requirements for stabilization of artificial and natural deposits and
slopes
8. Necessityofemployinggroundorundergroundstructuresinprojectsandtheirdesign
9. Siteresponsetoseismicloadsoranyothernaturalorartificialgeohazards
10. Geoenvironmentalissues,healthandsafetyhazards,andmanagementstrategies
Forsomerudimentaryprojectswithcommonenvironmentalconditions,theseitems
arerelativelystraightforwardandtherewouldbelittleneedforageotechnicalengineer
tointervene.Formoresophisticatedprojects,however,geotechnicalinvestigationsare
morecomprehensiveandrequireexpensiveexploration,testing,andinsightanalyses.
In sites with problematic soils, geotechnical concerns might dictate and control the
feasibility of projects from technical or economical aspects.