2.3 Material point method (MPM)

224 Pages·2013·14.53 MB·English

Formulation of a Dynamic Material Point Method and Applications to
Soil–Water–Geotextile Systems
VonderFakultätfürBau–undUmweltingenieurwissenschaften
derUniversitätStuttgart
zurErlangungderWürdeeinesDoktorsderIngenieurwissenschaften(Dr.-Ing.)
genehmigteAbhandlung,
vorgelegtvon
FURSAN M. HAMAD
ausBagdad,Irak
Hauptberichter: Prof.Dr.-Ing.PieterA.Vermeer
Mitberichter: Prof.Dr.-Ing.habil.ZdzisławWie˛ckowski
Mitberichter: Prof.Dr.-Ing.habil.ChristianMoormann
Mitberichter: Prof.Dr.-Ing.habil.BernhardWestrich
TagdermündlichenPrüfung: 28. Mai2014
InstitutfürGeotechnikderUniversitätStuttgart
2014
Mitteilung70
desInstitutsfürGeotechnik
UniversitätStuttgart,Germany,2014
Editor:
Prof.Dr.-Ing.habil.ChristianMoormann
c FursanHamad
(cid:13)
InstitutfürGeotechnik
UniversitätStuttgart
Pfaffenwaldring35
70569Stuttgart
Allrightsreserved. Nopartofthispublicationmaybereproduced,stored inaretrieval
system,ortransmitted,inanyformorbyanymeans,eletronic,mechanical,
photocopying,recording,scanningorotherwise,withoutthepermissioninwritingof
theauthor.
Keywords: Materialpointmethod,membranemodelling,soil–water–geotextilesystems
Printedbye.kurz+co,druckundmedientechnikGmbH,Stuttgart,Germany,2014
ISBN978-3-921837-70-2
(D93-Dissertation,UniversitätStuttgart)
Preface of the editor
The Institute of Geotechnical Engineering at the University of Stuttgart (IGS) publishes
with issue no. 70 of its proceedings the dissertation of Dr.-Ing. Fursan M. Hamad ti-
tled’FormulationofaDynamicMaterialPointMethodandApplicationstoSoil–Water–
Geotextile Systems’. The thesis presents a new and unique approach to simulate the
installation process and the behaviour of geosynthetics systems for geomechanical ap-
plications.
In recent decades geosynthetic materials have been increasingly used in geotechnical
and water engineering applications comprising reinforcement, protection, filtration and
screening. Especiallyincoastalandscourprotectionnewgeosyntheticconceptscombin-
ing geotextiles with available or dredged materials such as sand or slurry mixture have
proven as an efficient technical and economical alternative to conventional construction
materialslikerockorconcreteamourunits. Suchgeosynthetic–soilsystems,likegeotex-
tilebags,tubesorcontainers,havetobedesignedandmanufacturedinawaytosurvive
theinstallationprocessconsideringlargedisplacementsandwithstandtheoftenforbid-
dingworkingconditions.
The numerical simulation of such systems, i.e. modelling of a thin membrane in in-
teractionwithsoilofcomplexconstitutivebehaviourunderlargedeformation,isachal-
lenging task especially when additionally the fluid–structure interaction should also be
simulated. On modelling these problems with a Lagrangian finite element method, the
mesh can become too distorted and remeshing is essential. In the past decades, con-
siderable efforts have been made to adopt what is called meshfree methods to mitigate
the problems related to mesh distortion. One of these methods is the Material Point
Method (MPM) that represents the continuum field as Lagrangian material points (par-
ticles), which can move through the fixed background computational mesh. Within the
MPMframeworkDr. Hamadelaboratedanewmembranedevelopmentwhichmodelsa
tensilemembraneusingtwo–dimensionaltri–angularelements. Thismembranemeshis
freetomovethroughathree–dimensionalmeshofnon–structuredtetrahedralelements.
Coupling the finite element membrane with the MPM soil has more accurate and less
stressoscillationthantheclassicalMPMmembrane.
Dr. Hamad shows the great potential of the MPM method with the coupled formu-
lation of membrane by modelling different geotechnical applications of geosynthetics.
A challenging and very impressive application is to model the releasing of a geocon-
tainer from a split barge considering the interaction between the filled geotextile and
the barge as well as the fluid–geocontainer interaction during container sinking. The
effect of geocontainers’ interaction has been investigated by dropping a second geocon-
tainer. Another application which demonstrates the potential of the new approach for
many onshore geosynthetic systems is the investigation of the stability of a reinforced
embankment by simulating its failure mechanism. The effect of the embedded geotex-
tile is clearly illustrated on the displacement field which is referred to a non–reinforced
embankment.
The thesis of Dr. Hamad demonstrates that the simulation model he developed is
a powerful and versatile tool for a better understanding of the complex soil–water–
geotextileinteractionaswellasforthetechnicalandeconomicaloptimisationofinnova-
tivegeosyntheticsystems.
ChristianMoormann
Stuttgart,July2014
Preface of the supervisor
InrecentyearscoupledEulerian–LagrangianFiniteElementMethodshavebeenapplied
successfully for solving large–deformation problems, e.g. for simulating pile driving,
butitisdifficulttoextendthisapproachstraightforwardlytosoil–fluidinteractionprob-
lems as typical in branches of geotechnical engineering. For this reason, I have intro-
duced the so–called Material Point Method (MPM) at the Institute for Geotechnical En-
gineering of Stuttgart University in 2005. Professor Zdzisław Wie˛ckowski, the second
supervisorofthisthesisbyFursanM.Hamad,largelyinspiredmetodoso.
This thesis by Fursan M. Hamad is the third one in row on MPM that I supervised at
Stuttgart University. The first one by Lars Beuth (2012) is on quasi–static problems and
single–phase material behaviour. The second one by Issam Al–Kafaji (2013) includes
dynamicalproblemsandtwo–phasematerialbehaviour,i.e. thegenerationanddissipa-
tion of excess pore–pressures in water–saturated soil. In the present thesis on MPM by
FursanHamadextensionismadetofreewater,i.e. thefieldofComputationalFluidDy-
namics(CFD).Moreoveranovelelegantwayofmodellinggeomembranesisintroduced
and shown to be by far superior to an existing approach. Finally numerical procedures
areappliedtosimulatethedroppingofso–calledgeocontainersinwater.
On considering both free water and groundwater, numerical solutions of boundary–
valueproblemstendtosufferfromspuriouspressureoscillations,atleastonusingMPM.
I am extremely happy that Fursan found a remedy by introducing an averaged (nodal)
waterpressure.
Before coming to Stuttgart Fursan Hamad as well as his colleague Issam Al–Kafaji
were employed at the University of Baghdad, but because of the political situation it
was hardly possible to maintain contact to this university. No doubt, the fracturing of
Iraq has significantly damaged this previously strong university. However, I am happy
toobservethatalumni,likeFursanHamad,aredoingsowell.
After his first year as a PhD student at the University of Stuttgart Fursan continued
his work for nearly two years at the consulting and research establishment ’Deltares’ in
Delft, The Netherlands. This stay at Deltares was possible with financial support from
the European Commission, being embedded in the so–called ’Geo–Install’ project; an
IAPP project within the framework of the European Marie Curie FP7 research funding
programme. It provided Fursan the opportunity of working also in an industry envi-
ronment and obviously in another European country. No doubt, Fursan had to adjust
himself to different ways of working and together with his family he had to get used
to different places of living. However, despite such disruptions Fursan maintained full
focusonhisworkandcontributedsignificantlytofurtherdevelopmentsofMPM.
PieterA.Vermeer
NederhorstdenBerg,Netherlands,July2014

Acknowledgments
Firstandforemost,Iwouldliketoexpressmysincereappreciationtomythesissupervi-
sor Professor Pieter Vermeer for his guidance, inspiration and patience throughout my
PhD study. His advices on research as well as professional practice have been priceless
without it, I would never walk so far on the academic road. My gratitude extends to
ProfessorZdzisławWie˛ckowskiforthepreciouscontributionwiththeprecisionofame-
chanicalengineer. IwantalsotothankProfessorChristianMoormannforthesignificant
support to get my thesis done. Last but not least, I warmly thank Professor Bernhard
Westrichfortheinvaluabledailydiscussions.
Here, I would like to especially thank Professor Dieter Stolle for sharing ideas and
the friendly encouragements, you have been a tremendous mentor for me. Likewise, I
express my appreciation to Dr. Issam Al–Kafaji and Dr. Corné Coetzee for introducing
metotheMPMworld. Special thankstotheEuropean project(Geo–Install)represented
by its coordinator Professor Minna Karstunen and the people involved in this project:
Professor Adam Bezuijen, Dr. Alexander Rohe, Shuhong Tan, Phuong Nguyen, Wiep
Hellinga and others. Furthermore, I feel glad to Dr. Martino Leoni as well as Dr. David
Mašínfortheirhelp.
In Stuttgart, I have shared nice memories with great support. Particularly, from the
IGS people: Bernd Zweschper, Dr. Maximilian Huber, Dr. Annette Lächler, Dr. Axel
Möllmann, Ruth Rose, Nadja Springer, Sylvia Eckard, Dr. Syawal Satibi, Dr. Mar-
cus Schneider, Reinhold Mößner, Stephan Ries, Johannes Aschrafi, Seyedfarzad Fatem-
izadeh,LinusKlein,JuliaKnopp,PatrikBuhmannandDominikGünther. FromtheUni-
versity of Baghdad, I acknowledge the support of Oday Abdullah, Dr. Asmaa Rashid,
andYihyaHamad.
Finally, I am deeply indebted to my parents, brothers and sisters. A special apprecia-
tiontomywifeandmylittledaughterfortheirendlesslove,supportandunderstanding.
FursanHamad
Stuttgart,July2014