Numerical Modelling of Coastal Structures Armoured with Concrete Units

281 Pages·2015·18.5 MB·English

Numerical Modelling of
Coastal Structures Armoured with Concrete Units

Anastasaki Eleni
September 2015

Department of Earth Science and Engineering
Imperial College London

A dissertation submitted to the Department of Earth Science and
Engineering of Imperial College London in partial fulfillment of the
requirements for the degree of Doctor of Philosophy
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‘The copyright of this thesis rests with the author and is made available under a Creative Commons
Attribution Non-Commercial No Derivatives licence. Researchers are free to copy, distribute or
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purposes and that they do not alter, transform or build upon it. For any reuse or redistribution,
researchers must make clear to others the licence terms of this work’

Eleni Anastasaki
PhD Student
Department of Earth Science and Engineering
Imperial College London

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The research of this thesis was carried out in the Department of Earth Science and Engineering at
Imperial College London (EPSRC grant EP/H030123/1). Although I worked as a team with my
supervisor Dr J-P Latham and with Dr J. Xiang, who is responsible for the development of the
numerical code, the material in this thesis is entirely the result of my own research. Any contribution
from the other members of the team to this work is appropriately identified and acknowledged in
the thesis.
A large part of the material of this thesis has been published and/or submitted for publication in
international scientific journals and proceedings of international conferences. However, no part of
this work has been previously submitted to this or any other academic institution for a degree or
diploma, or any other qualification.

Eleni Anastasaki
PhD Student
Department of Earth Science and Engineering
Imperial College London

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ABSTRACT
Looking to a future where the structural stability of single concrete armour layers is based
upon numerical investigation, this thesis addresses the first major task, which is the representation
of real structures. Coastal structures armoured with concrete units are created in prototype
dimensions in a numerical model with satisfied realism for first time. The available 3D computer
model based on FEMDEM (the combined finite-discrete element method), which has the capability
for multi-body simulation of complex shaped objects, was used.
A major challenge was to develop a methodology for the numerical creation of concrete
armour layers that would satisfy the stringent criteria required by the designers of breakwater units
for on-site constructed ‘random’ and ‘interlocking’ systems. A novel feature to obtain realistically
tight systems is the use of four initial types of regular orientations of units, which are sequenced
appropriately on a pre-defined positioning pattern grid. This new methodology enables different
armour layer models to be built, characterised and examined.
The scope of the study is limited to dry conditions and performance under oscillatory loading
is investigated by means of vibration. Design variables such as initial packing density, underlayer
roughness and number of rows are evaluated and the technical criteria are challenged. The use of a
different type of unit shape is also examined to show the potential of the developed technology. A
set of analysis tools including accurate calculation of packing density on a local and global basis and
the distribution of unit displacements after disturbance were developed to evaluate designs.
It is confirmed that the packing density is the most important parameter, which influences
the performance of armour layers; the tighter the packs, the less are the displacements of units
under disturbance. A single armour layer with low number of rows of units also proved to be stable.
It is easier for units placed on a relatively smooth underlayer to find tighter positions, causing higher
values of total average packing density. But when disturbed, armour layers placed on a rough
underlayer are more stable. The use of a different type of unit shape is also examined in this thesis,
with the purpose to present the potential of the developed technology to such applications.
Results may be considered to have limited applicability to the real behavior of structures
under wave action. However, they provide some insights into how such complex coastal structures
behave. This research constitutes a stepping stone on the way to models that accommodate wave
action and will may one day improve the engineering design and understanding of movement of
these concrete armour units.

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ACKNOWLEDGEMENTS
I owe my sincere gratitude to my supervisor Dr J-P Latham, for giving me the opportunity to
accomplish my PhD studies under his supervision, for his trust, help and constant support. I also owe
special thanks to Dr J. Xiang for his patience, the guidance and the great assistance he offered me, as
well as for his daily support on various matters.
I would like to express my gratitude to the members of the engineering companies Artelia
Group, and Baird and Associates, and especially M. Fons, N. Garcia and B. Baird for the very useful
information they provided during our meetings at Imperial College London. To receive training in the
placement of CLI units I had the opportunity to undertake two visits to HR Wallingford in May and
June of 2011 for which I am grateful. During my research I took the initiative to visit the marina in
Limassol, Cyprus, in December 2012, during the construction of the breakwater sections made of
Accropode I; I would like to thank T. Vezyrianos, Technical Manager, Salfo and Associates SA for
showing me the structures. I also took the initiative to request information regarding the
construction of the Colombo Breakwater, which consists of Core-Loc units; I thank Peter Neville-
Jones, Technical Director, Maritime and Ports, URS Infrastructure & Environment UK Limited for his
prompt response.
During my PhD life, I was blessed to meet Stelios Karagiorgis, my beloved husband and give
birth to our adorable son, Antony, ‘our miracle’, in January 22, 2014. I was very lucky to have met my
best friends at Imperial College London. Nikos Karantzoulis, George Marketos, Nikolas Kantas were
the witnesses in my wedding. Alexandra Spachis and Yannis Kiskiras are the godparents of my son. I
feel grateful for all the support they offered me during my PhD and very happy for having them in
my life.
The decision to move to London and to pursue my PhD was persistently supported by my
affectionate and dedicated mother, Maria Anastasaki. The constant encouragement by my best
family friend Kelly Galanopoulos kept me motivated and determined. My brother, Manolis
Anastasakis has always been supporting me. I started this PhD with a strong theoretical background
and a rich professional experience, which I gained by working closely with Professor C.I. Moutzouris
(Rector of National Technical University of Athens) at the Laboratory of Harbour Works of NTUA
between 1999 and 2011. I completed this PhD with the continuous support and patience of my
husband. The help of my mother was truly necessary.

I dedicate this PhD thesis to my lovely family, to the dear men of my life Stelios & Antony!

I deeply feel my father is very proud of his daughter!
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