2024年3月15日发(作者：纽曼手机官网旗舰店)

GeotechGeolEng(2008)26:705–727

DOI10.1007/s10706-008-9204-5

ORIGINALPAPER

MicrostructureInvestigationinUnsaturatedSoils:

AReviewwithSpecialAttentiontoContributionofMercury

IntrusionPorosimetryandEnvironmentalScanning

ElectronMicroscopy

EnriqueRomeroÆ

Received:11August2007/Accepted:3April2008/Publishedonline:15May2008

ÓSpringerScience+BusinessMediaB.V.2008

AbstractWiththeadventofmodernmicrostruc-

turaltestingtechniquesandmicrostructurebased

constitutivemodelsthemicrostructuralcharacterisa-

per

reviewsthehistoryofmicrostructureinvestigationin

unsaturatedsoilsanddiscussestheengineeringsig-

nifibrief

overviewofthemainmicrostructuraltechniques,the

paperfocusesontheevaluationofthecurrentstateof

useandthedevelopmentoftwowidelyusedtech-

niquestostudythemicrostructureofpartially

saturatedsoils,namelymercuryintrusionporosimetry

andtheenvironmentalscanningelectronmicroscopy.

Thedetailsofthesetechniques,theiradvantagesand

limitations,arefirstcovered,followedbythepresen-

esultshighlight

theuseofthesetechniquesforunderstandingdifferent

hydro-mechanicalbehaviouralfeaturesobservedat

fically,thepapershowsthe

useofthesetechniquestoexplorethefundamental

propertiesofwaterretentioncharacteristics,water

(&)

DepartmentofGeotechnicalEngineeringand

`

cnicadeCatalunya,Geosciences,UniversitatPolite

´

duloD2,c/JordiGirona,1-3,CampusNord,mo

08034Barcelona,Spain

e-mail:-morales@

DepartmentofCivilandEnvironmentalEngineering,

CarletonUniversity,Ottawa,Canada

e-mail:Paul_simms@

permeability,andmicroandmacrostructuralinterac-

tionsalongdifferenthydro-mechanicalpaths.

KeywordsMicrostructureÁ

MercuryintrusionporosimetryÁ

PoresizedistributionÁ

EnvironmentalscanningelectronmicroscopyÁ

UnsaturatedsoilÁSuction

1Introduction

Microandmesostructuralstudiesareincreasingly

usedtoimproveunderstandingofthemacroscopic

behaviourandphysicalpropertiesofcompacted

tructuralstudiesinvolve

theuseoftechniquesatparticle/aggregationscale

(100lm)toanalysethearrangementanddistribu-

tionofparticles,particleassembliesandpores—and

theircontactsandconnectivity—indifferentsoils

(CollinsandMcGowan1974;DelageandLefebvre

1984;Delageetal.1996,Al-RawasandMcGown

1999;MitchellandSoga2005).Mesostructuralscan-

ningtechniquesusingtime-domainreflectometry,

near-infraredspectroscopicmeasurements,electric

impedancetomography,neutrontomography,X-ray

computedtomography,dual-energygamma-raytech-

nique,andsoon,goastepforwardintheanalysed

scale(BakerandAllmaras1990;Fukueetal.1999;

Borsicetal.2005;Desruesetal.2006).However,

muchmorepowerfulX-raysprovidedbysynchrotron

123

706

radiationandmicrofocusX-raysystemshaverecently

allowedmovingastepforwardintheanalysed

domainandgoingtomicrometricscale,narrowing

thegapbetweenmesoandmicrostructuraltechniques

(Be

´

suelleetal.2006,Takahashietal.2006).Recent

applicationsofthesemesostructuraltechniquesin

unsaturatedsoilshavebeendevotedtothemonitoring

ofhydro-chemo-mechanicalprocesses(Cominaetal.

2008),tothedetectionofdesiccationcracks(Gebre-

negusetal.2006;Mukunokietal.2006),tothe

visualisationofdiffusion/hydrationphenomenaandto

thestudyoffluidmovements(Rollandetal.2003;

Rollandetal.2005;VanGeetetal.2005;Rodrı

´

guez-

Reyetal.2006;Carminatietal.2006;Kolijietal.

2006a).

SincethepioneeringworksofBarden(1973),

Bardenetal.(1973),Collinsetal.(1973),Tovey

(1973),Toveyetal.(1973),CollinsandMcGown

(1974),McGownandCollins(1975),Grabowska-

Olszewska(1975)andOsipovandSokolov(1978a,c)

onthemicrostructureofnaturalcollapsibleand

expansivesoils,theincreasinguseofmicrostructural

studieshaveledtoimprovedtechniquesandtheir

turatedsoils,microscopic

examinationofthesoilstructurehavetraditionally

concentratedoncompactedsoils,focusingonthe

aggregationormatrixstructureofdifferentstatesinthe

dynamiccompactioncurve,aswellasontheir

relationshipwithmainpropertiesrelatedtoengineer-

ingbehaviour,suchasstrength,compressibilityand

waterpermeability(BardenandSides1970;Ahmed

etal.1974;OsipovandSokolov1978b;Garcia-

Bengocheaetal.1979;Prapaharanetal.1985,1991;

Tessieretal.1992;Delageetal.1996;Delageand

Graham1996).Thesestudieshaveillustratedthatthe

microstructureofagivencompactedsoilisnotunique,

andstronglydependsonthepathsfollowedtoreacha

ionhave

beenalsodevotedtothemicrostructureofnatural

swellingclays(Toveyetal.1973;Al-Rawasand

McGown1999),atopicthathasrecentlygained

increasingconsiderationwithinthecontextofclay-

basedengineeringbarriersforradioactivewastedis-

posal(Wanetal.1995;Al-Mukhtaretal.1996;

Saiyourietal.1998;Romeroetal.1999;Puschetal.

1999;Saiyourietal.2000;Cuietal.2002;Puschand

Yong2003;Lloretetal.2004;Saiyourietal.2004;

CuisinierandMasrouri2005;Delage2006,2007;

DelageandCui2007).

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GeotechGeolEng(2008)26:705–727

Understandingsoilmechanicsatthemicroscopic

levelisparticularlypertinenttounsaturatedsoils—

specificallyclay-basedmaterials,whosebehaviouris

complicatedbythepresenceofbothairandwaterin

undamentalpointofview,

measurementsandobservationsatthemicrostructural

levelinvolvingclayunitsandtheiraggregationsare

veryimportant,sincetheyhelpinfurtherunderstand-

ingofhigherstructurallevels,theirinteractions,the

stabilityofthearrangementsandtheirconsequences

formaterialpropertiesandbehaviourundervarious

tion,

thesetechniquescanbeusedtomonitorthechanges

undergonebyunsaturatedmaterialsataggregateand

aggregateassemblyscales,whensubjectedtocom-

way,the

methodsarehelpfulinrelatingmicrostructureto

macroscopicbehaviour,forexampleinbuildingup

multi-structureconstitutivemodelswithcoupling

functionsbetweenthedifferentstructurallevels

(e.g.,Alonsoetal.1999;LoretandKhalili2000;

Alonsoetal.2005;Sa

´

nchezetal.2005).

Thepaperstartswithareviewoftheliteraturethat

explorestherelationshipofsoilmicrostructureto

engineeringproperties,followedbysectionsdescrib-

ingtechniquesspecificallyaimedatcharacterisingthe

hevari-

ousavailabletechniquesusedtostudyunsaturatedsoil

microstructure,mercuryintrusionporosimetry(MIP)

andenvironmentalscanningelectronmicroscopy

(ESEM)aregivenspecialattentioninthereport:the

formertechniquehasbeenveryfrequentlyusedwhile

thelatterisanemergingtechniquewithgreatpotential

wellasdetailedtechnicaldescriptionsanddiscussion

ofadvantagesandlimitationsofeachmethod,thebody

ofresearchperformedusingeachtechniqueis

erconcludeswitha

discussionoffutureresearchdirections.

Itisadifficulttasktomakearepresentative

selectionofthetechniques,theiruseandinterpreta-

tion,sinceitisanexperimentalsubjectofinterestfor

geologists,soilscientistsandgeotechnicalengineers.

Infact,muchofthepreviousworkonthemicrostruc-

tureoffine-grainedsoilswasinitiatedbysoilscientists

anddevelopedbyengineeringgeologistswithinthe

frameworkofhighlysensitivepost-glacialclaysand

softsoils(Gillott1970,1979;Pusch1970;Delageand

Lefebvre1984;Bennetetal.1991).Thereadermay