Thesis (MEng)–Stellenbosch University, 2014. / ENGLISH ABSTRACT: The Port of Durban is forecasted to reach its capacity in terms of container handling soon,
which necessitates the investigation of an alternative port in the vicinity. The old Durban
Airport site has been identified as a potential location to develop a new deep water
container harbour. This is driven by a demand for deep water berth capacity as a result of
shipping liners preferring the benefits of scale in their operations, leading to the use of
larger ships with deeper drafts. To protect the new port from wave energy penetrating
inside the basin as well as from sedimentation from the adjacent beaches, the design and
construction of breakwaters are required.
The proposed main breakwater for this dig-out port is expected to extend 1 200m into
the sea, up to depths of 30m at the seaward roundhead. The deeper parts of the
breakwater face wave onslaught in a different manner than a conventional breakwater in
shallower waters. At these larger depths, the breakwater has to dissipate the energy of
non-breaking waves.
In this thesis, the wave climate nearshore, adjacent to the proposed breakwater is studied
and extreme wave events are simulated with a SWAN numerical model. The results for a
range of wave conditions, corresponding to selected events up to a return period of one in
100 years, are presented.
A study of deep water breakwaters was undertaken to investigate other examples of
similar structures. This indicated a clear distinction between vertical wall type
breakwaters and the more traditional rubble-mound type breakwaters. For this thesis, a
rubble-mound breakwater was chosen as the breakwater type for testing under
conditions of the Durban Dig-Out Port (DDOP). Focussing on a deep water trunk section
of the proposed main breakwater, a concept cross-section was designed using
deterministic design methods. The formulae incorporated in this method did however not
take into account the packing density of the armour layer and only assumed the
recommended values.
The hypothesis is thus put forward that the breakwater will still be hydraulically stable
for packing densities below the recommended values. This would decrease material
consumption and save on cost over the entire breakwater. A physical model was designed
to experiment with different armour layer configurations of single- and double layer
Cubipod arrangements. The unit was chosen for its massive shape and structural integrity
even during impact. A physical model study was performed at the facilities of the CSIR in Stellenbosch. It
entailed setting up a fixed-bed two-dimensional physical model in a glass wave flume.
Measuring wave heights, wave reflection, overtopping, wave transmission and armour
damage, the hydraulic stability and operational performance were analysed for several
tests. Based on the results of the first few test series, alterations were made to the
breakwater geometry and armouring.
The results confirmed the hypothesis that lower packing densities were still hydraulically
stable under 1 in 100 year return period wave conditions without inhibiting operational
performance. A final cross-section is presented as concept design for the deep section of
the proposed DDOP main breakwater. / AFRIKAANSE OPSOMMING: Volgens vooruitsigte gaan Durban hawe binnekort sy kapasiteit bereik wat die hantering
van skeepshouers betref. Hierdie verwikkeling noodsaak die ondersoek na ‘n
alternatiewe hawe in die nabye omgewing. Die voormalige Durban lughawe is intussen
geïdentifiseer as ‘n potensiële perseel waar ‘n diep water houervrag hawe ontwikkel kan
word. Dit word gedryf deur die aanvraag na diep water kaai kapasiteit as gevolg van skip
operateurs wat skaalvoordele verkies, sodat groter skepe met diep rompe meer populêr
word. Die ontwerp en konstruksie van breekwaters word dus benodig, om te verhoed dat
beide golwe, sowel as sediment van aangrensende strande, die hawe binnedring.
Die voorgestelde hoof breekwater vir hierdie hawe sal na verwagting tot 1200m in die
see in strek, waar dit tot 30m diep is naby die seewaartse hoof van dié breekwater. Die
dieper gedeeltes van só ‘n breekwater sal blootgestel word aan ‘n ander soort golf aanslag
as ‘n soortgelyke konvensionele breekwater in vlakker water. In hierdie waterdiepte is
die breekwater verantwoordelik vir die energie verbreking van ongebreekte golwe.
In hierdie tesis word die golfklimaat langs die kus, naby aan die voorgestelde breekwater
bestudeer. Die uiterste golf gebeurtenisse word gesimuleer met ‘n SWAN numeriese
model. Die resultate van ‘n reeks golf kondisies, ooreenstemmend met bepaalde
gebeurtenissemet herhaal periodes van tot 100 jaar, word aangebied.
‘n Studie van diep water breekwaters is onderneem om voorbeelde van soortgelyke
strukture te ondersoek. Die studie toon ‘n definitiewe onderskeid tussen vertikale muur
breekwaters en die meer tradisionele “rubble-mound” breekwater tipes. Vir hierdie tesis
is die “rubble-mound” breekwater tipe gekies vir toetsing, onderhewig aan die kondisies
van die “Durban Dig-Out Port” (DDOP). ‘n Konsep deursnit is ontwerp vir ‘n diep water
romp gedeelte van die voorgestelde hoof breekwater, deur van deterministiese metodes
gebruik te maak. Die formules soos vervat in hierdie proses maak egter nie voorsiening
vir die pakdigtheid van die bewapeningslaag nie, maar aanvaar slegs die voorgestelde
waardes.
Die hipotese word dus aangevoer dat die breekwater steeds hidrolies stabiel sal wees vir
pakdigthede wat laer as die voorgestelde waardes is. Dit sal die verbruik van materiale
verlaag en lei tot koste besparings vir die breekwater. ‘n Fisiese model is ontwerp om te
eksperimenteer met verskillende opstellings van die bewapeningslaag. Dit sluit enkel- en
dubbel laag bewapening met Cubipod eenhede in. Hierdie eenheid is gekies vir sy
massiewe vorm en strukturele integriteit, selfs tydens impak. ‘n Fisiese model studie is uitgevoer by die fasiliteite van die WNNR in Stellenbosch. Dit
het die opstel van ‘n vaste-bodem, twee-dimensionele fisiese model in ‘n glas golftenk
(“wave flume”) behels. Hidroliese stabiliteit en operasionele werksverrigting is
geanaliseer deur golf hoogtes, -weerkaatsing, -oorslag, -deurlating, en skade aan die
bewapening te meet vir verskeie toetse. Gebasseer op die resultate van die eerste paar
toetsreekse, is veranderinge gemaak aan die breekwater se geometrie en bewapening.
Die resultate het die hipotese bevestig dat laer pakdigthede steeds hidrolies stabiel is
tydens golf kondisies met ‘n 1 in 100 jaar herhaal periode, sonder om die werksverrigting
van die breekwater te belemmer. ‘n Finale deursnit word voorgestel as ‘n konsepontwerp
vir die diep water deursnit van die DDOP se hoof breekwater.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/95969 |
| Date | 12 1900 |
| Creators | Wust, Isak |
| Contributors | Toms, Geoff, Stellenbosch University. Faculty of Engineering. Department of Civil Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xiii, 90 p. : ill. |
| Rights | Stellenbosch University |
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