Cement grouting during installation of ground anchors in non-cohesive soils

223 Pages·2015·16.71 MB·English

Xenia A. L. Domes
Cement grouting during
installation of ground anchors
in non-cohesive soils
Thesis for the degree of Philosophiae Doctor
Trondheim, June 2015
Norwegian University of Science and Technology
Faculty of Engineering Science and Technology
Department of Civil and Transport Engineering
Prefa
e
The presented PhD study was carried out in cooperation with the Norwegian University of
Science and Technology in Trondheim, Norway and the Federal Waterways Engineering
and Research Institute in Karlsruhe, Germany. This project was made possible by financial
supportoftheFederalWaterwaysEngineeringandResearchInstituteinKarlsruhe. Thefield
tests were carried out at their sites. The laboratory test series were done and test equipment
was designed at the Norwegian University of Science and Technology. Their support is
gratefullyacknowledged. Thework ispresented as monograph.
i

Abstra
t
Pressuregroutingduringinstallationofgroutedgroundanchorsisknowntoincreaseanchor
capacity in non-cohesive soils, but little information is available on correlations between
applied grouting pressures, duration of grouting, ground conditions and increase of anchor
pull-outcapacity.
The presented PhD study is concerned with processes taking place during installation
of grouted ground anchors in non-cohesive soils, where filtration of the cement grout is
assumed. Itwasaimedtodeterminetheinfluenceofpressuregroutingonthestressesonthe
anchor body and the properties of the adjacent soil. The knowledge of those is considered
prerequisiteinorderto determinetheanchors pull-outcapacity.
In the first part of the PhD thesis, a series of laboratory experiments is presented, which
was carried out to understand the filtration process of cement grouts and to determine the
properties of the filter cake material. Using a filtration press the rate of filter cake build-up
was investigated,takingintoaccount theinfluence ofgroutingpressureand initialwater/ce-
mentratioofthegrout. Thetestresultswereusedtoevaluatedifferentanalyticalapproaches
to simulate the filtration process: a two-phase filtration model and classical consolidation
theory. Both models were found appropriate, and calculation parameters were determined.
In addition to the filtration tests, the mechanical properties of the fresh, uncured, filter-cake
material were investigated. Applying soil mechanical investigation methods, strength and
stiffnesspropertiescould bedetermined.
In the second part of the PhD thesis in-situ tests during anchor installation in sands are
presented. On three test sites the grout pressure was measured inside the borehole during
and after anchor installation. Measurements confirmed a grout filtration inside the borehole
and indicated the increase of radial stresses on the anchor body. Additional flat-dilatometer
soundings (DMT) and cone penetration tests (CPT) showed the influence of the grouting
processon theradialstresses intheadjacentsoil.
In thethird part ofthe thesisa numerical model is proposed to simulatethe filtrationpro-
cess of cement grout in a fullycoupled flow-displacementfiniteelement analysis. Based on
the two-phase filtration model a filter criterion was implemented, which defines the phase
change from liquid to solid grout based on the discharge of water. The phase change was
realisedbychangingthematerialpropertiesofthegroutelements. Withthepresentedmodel
thegroutingduringanchor installationwas simulatedand theinfluenceofdifferent parame-
terscouldbedetermined. Thetransferofgroutingpressuresfrom theliquidgrouttothesoil
through seepage forces in the filtercake is simulated and the residual stresses after grouting
determined.
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The findings can now be used as starting point to simulate the load transfer mechanisms
ofgroutedground anchorsin numericalanalysis,takingintoaccountinstallationeffects.
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A
knowledgements
During my PhD research I had the privilege to be part of the geotechnical groups at the
Norwegian University of Science and Technology (NTNU) in Trondheim as well as at the
Federal Waterways Engineering and Research Institute (BAW) in Karlsruhe. However, I
started my academic career setting me off into the topic of grouted ground anchors at the
structural engineering department at the University of Applied Sciences in Münster. Along
thewayImetmanypeoplewhohavebeensupportivetomeand mystudyinonewayorthe
other. Iwouldliketo expressmydeepest gratitudetoall ofthem.
Firstandforemost,IwouldliketothankmysupervisoratNTNU,ProfessorThomasBenz,
for his support and encouragement. Thank you for always having an open mind for ideas
and discussion,beinginterested and curiousabout myresearch, providingscientificsupport
andevenhelpingmeinthefield, givingmeconfidenceand keepingmemotivated.
I also owe my gratitude to my supervisor at BAW, Dr. Markus Herten, without whom it
would not have been possibleto conduct this research project. Thank you for your support,
forhavingfateintheresearch projectand facilitatingthepossibilitiesI had.
Further, I would like to thank Professor Gerhard Schaper of the FH Münster for evoking
myinterestin research and encouragingmetodo aPhD.
Theexperimentalpartofthisworkwouldhavebeenimpossiblewithoutthehelpandeffort
ofthetechnicalstaffatNTNU. ThankyouFrank Stæli, TageWestrumand PerØstensenfor
building the sensors and laboratory equipment and managing to get them ready in time so
that I could finish my experiments within the tight travel schedule. Also many thanks to
RikkeMarieVollan forhelpingmewiththelaboratoryexperiments.
IamgratefulforthesecretaryoftheGeotechnicalDivisionMaritSkjåk-Brækforpatiently
helping me with all organizational and administrativematters and always being there when
helpisneeded.
Overtheyears Ihaveenjoinedmanydiscussionsandmeetingswithpastand presentPhD
candidates of different organizations. All of you provided inspiration and help which is
highly appreciated. Amongst all other things, special thanks to Priscilla for supporting me
topreparefortheexamsatNTNU,Annikaforthesupportwithadministrativematters,Stian
for keeping the agenda up to date and Hilde for introducing me to the Norwegian culture. I
would also like to thank Harriet, Jakob and Katharina for their versatile support and com-
panionship.
ManythankstoallmycollegesatBAW,whoprovidedaninspiringandwelcomingwork-
ingenvironment. Thankyouforthemanysuggestionsandcoffeebreakdiscussions. Special
thanks to EvaDornecker for sharing your knowledgeabout grouted ground anchors. Thank
v
you to Regina Kauther, Ingo Feddersen, Björn Mettig and Hermann Brauer for the support
during the in-situ tests. I would also like to thank Dr. Bernhard Odenwald for the inspir-
ing discussions about analytical solutions. I must also thank Olivia Wenzel for proofread-
ing/editingmythesis.
Finally,my deepest gratitudegoes to my family and friends with theirunconditionalsup-
port,everyoneintheirownway. Thankyoutomyfatherformotivatingmeachievingagoal
and teaching me to become an independent person. Thank you Mama for your love and
moralsupportregardlessthetimeordistance. ThankstomysistersLauraandSophiaforun-
derstanding and being patient. And last but not least I would like to thank my dear husband
Fabian who accompanied me during the journey towards completing my PhD study. Thank
you for encouraging me, enduring me and being faithful. You have been solid as a rock for
me.
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Table of Contents
1 Introdu
tion 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Scope andlimitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 Outlineofthethesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Grouted ground an
hors 5
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2.1 Groutedground anchors . . . . . . . . . . . . . . . . . . . . . . . 5
2.2.2 Micropiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2.3 Installationmethodsofanchors . . . . . . . . . . . . . . . . . . . 6
2.2.4 Anchordesign . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3 Fundamentalsand historicreview . . . . . . . . . . . . . . . . . . . . . . 8
2.3.1 Processes duringgroutingofgroundanchors . . . . . . . . . . . . 10
2.3.2 Influence ofgroutingpressureonanchorcapacity . . . . . . . . . . 11
2.3.3 Increase ofradialstresses dueto swellingofcement grout . . . . . 13
2.3.4 Characteristics ofthegroutbody . . . . . . . . . . . . . . . . . . . 13
2.3.5 Influence ofthedrillingmethods . . . . . . . . . . . . . . . . . . . 16
2.3.6 Groutabiliy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.4 Chapter summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3 Cement grout (cid:28)ltration - Ba
kground 21
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.2 Fundamentalsofcement groutfiltration . . . . . . . . . . . . . . . . . . . 21
3.2.1 Two-phasefiltrationmodel . . . . . . . . . . . . . . . . . . . . . . 22
3.2.2 Consolidationtheory . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.3 Analyticalsolutionofradial filtrationwithconstantpumpingrate . . . . . . 24
3.4 Theoretical considerationsabout cementgroutfiltercake . . . . . . . . . . 25
3.5 Material propertiesoffresh cement grout . . . . . . . . . . . . . . . . . . 26
3.5.1 Previouslaboratory testsoncement groutfiltration . . . . . . . . . 27
3.5.2 In-situmeasurements . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.6 Chapter summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
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TableofContents
4 Cement grout (cid:28)ltration - Laboratory tests 31
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.2 Filtrationtests-Experimentalprocedure . . . . . . . . . . . . . . . . . . . 31
4.2.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.2.2 Filtrationpress . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.2.3 Experimentalprocedure . . . . . . . . . . . . . . . . . . . . . . . 32
4.2.4 Testseries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.2.5 Watercontentmeasurements . . . . . . . . . . . . . . . . . . . . . 33
4.2.6 Permeabilitymeasurements . . . . . . . . . . . . . . . . . . . . . 34
4.3 Filtrationtests-Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.3.1 Filtrationbehaviour . . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.3.2 Influenceofsand as filtermedium . . . . . . . . . . . . . . . . . . 37
4.3.3 Injectionofgroutintosand . . . . . . . . . . . . . . . . . . . . . . 37
4.3.4 Phasechange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.3.5 Watercontents . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
4.3.6 Permeabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.3.7 Filtrationrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.4 Simulationoffiltrationtests . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4.4.1 Filtrationmodel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4.4.2 Consolidationtheory . . . . . . . . . . . . . . . . . . . . . . . . . 46
4.4.3 Modifiedconsolidationtheory . . . . . . . . . . . . . . . . . . . . 48
4.4.4 Estimationoffiltercake thickness . . . . . . . . . . . . . . . . . . 49
4.4.5 Comparisonoffiltrationandconsolidationtheory . . . . . . . . . . 49
4.5 Mechanical propertiesoffresh cementgrout filtrate . . . . . . . . . . . . . 51
4.5.1 Soilmechanical testsonfiltercake material . . . . . . . . . . . . . 51
4.5.2 Soilmechanical propertiesofuncured cementgrout filtrate . . . . . 52
4.6 Chaptersummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
5 Installation e(cid:27)e
ts - Field measurements 59
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
5.2 Testsitesand testprogramme . . . . . . . . . . . . . . . . . . . . . . . . . 59
5.2.1 TestsiteDörverden . . . . . . . . . . . . . . . . . . . . . . . . . . 59
5.2.2 TestsiteVenhaus . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
5.2.3 TestsiteHorstwalde . . . . . . . . . . . . . . . . . . . . . . . . . 65
5.3 Testmethods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
5.3.1 Pressuremeasurementswithintheborehole . . . . . . . . . . . . . 67
5.3.2 Flat DilatometerTests (DMTand DMTA) . . . . . . . . . . . . . . 70
5.4 Field testresults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
5.4.1 MeasurementsinDörverden . . . . . . . . . . . . . . . . . . . . . 73
5.4.2 MeasurementsinVenhaus . . . . . . . . . . . . . . . . . . . . . . 78
5.4.3 PressuremeasurementsinHorstwalde . . . . . . . . . . . . . . . . 89
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TableofContents
5.4.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
5.5 Conclusionoffield measurements . . . . . . . . . . . . . . . . . . . . . . 101
6 Modelling
ement grout (cid:28)ltration with FEM 103
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
6.2 Implementation of cement grout filtration into the finite element method
(FEM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
6.2.1 Filtercriterion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
6.2.2 Identificationofneighbouringelements . . . . . . . . . . . . . . . 106
6.2.3 Dischargeintotheadjacentfilter elements . . . . . . . . . . . . . . 106
6.2.4 Calculatingtheadvancingfiltrationfront . . . . . . . . . . . . . . 107
6.3 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
6.3.1 Constitutivelaws . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
6.3.2 Materialproperties . . . . . . . . . . . . . . . . . . . . . . . . . . 107
6.4 Validationofone-dimensionalcementgroutfiltration . . . . . . . . . . . . 108
6.4.1 Modeldefinition . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
6.4.2 Validationresults . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
6.5 Validationofradialcement groutfiltration . . . . . . . . . . . . . . . . . . 112
6.5.1 Modeldefinition . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
6.5.2 Validationresults . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
6.6 Cement groutfiltrationinsidetheborehole . . . . . . . . . . . . . . . . . . 114
6.6.1 Modeldefinition . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
6.6.2 Calculationsteps . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
6.6.3 Calculationmodes . . . . . . . . . . . . . . . . . . . . . . . . . . 118
6.6.4 Resultsofmodel‘G_LM’ . . . . . . . . . . . . . . . . . . . . . . 119
6.6.5 Meshdependency andfiltrationdirection . . . . . . . . . . . . . . 124
6.6.6 Resultsforfiltration inmainflow directiononly . . . . . . . . . . . 124
6.6.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
6.7 Parametricstudy-Radial flow . . . . . . . . . . . . . . . . . . . . . . . . 127
6.7.1 Modeldefinition . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
6.7.2 Calculationsteps . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
6.7.3 Radial stressesand deformationsusingHSsmallmodelforthesoil . 129
6.7.4 Variationofgroutingparameters . . . . . . . . . . . . . . . . . . . 131
6.7.5 Variationoffiltercake stiffness . . . . . . . . . . . . . . . . . . . 132
6.7.6 Variationoffiltercake permeability . . . . . . . . . . . . . . . . . 134
6.7.7 Variationofsoilpermeability. . . . . . . . . . . . . . . . . . . . . 136
6.8 Chapter summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
7 Con
luding remarks 141
7.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
7.2 Conclusionsand recommendationsforpractice . . . . . . . . . . . . . . . 144
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