Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: For the safekeeping or harbouring of small craft, whether for leisure or commercial use, a
tranquil basin is the principle requirement in designing a functional harbour facility. Waves
transmitted through the perimeter structures of a marina result in agitation of the basin and
thereby a reduction in tranquillity. Similarly, waves reflected off the perimeter structures that line
entrance channels could result in difficulty when manoeuvring through the entrance channel
water areas.
An alternative to the conventional breakwater becomes a necessity when the conventional
mass-filled or caisson breakwaters are not feasible in technical or financial terms. One of the
alternative options could be to consider a piled row breakwater. In broad terms, this consists of
closely spaced piles that attenuate wave energy whilst not forming an impermeable barrier,
allowing for currents and sediment to pass through. When comparing the different options for
creating a piled row breakwater the quantity of material used to achieve a desired level of wave
dissipation could be the most important aspect in considering possible alternatives, as this would
relate directly to construction costs and time when considering implementation.
A literature review revealed multiple references to theories that predicted the transmitted and
reflected waves for various breakwater porosities and wave conditions. However, there is limited
coverage in literature enabling prospective designers. For example, literature describing the
applicable ranges of shape configurations that one should start off with when developing
concepts is not readily available.
This thesis study used physical modelling to compare the wave transmission properties of
breakwaters comprised of three different piled element shapes, namely round, square and
diagonal square piles. The pile element shapes are compared for varying porosity values over a
range of input wave parameters. A comparison of the transmission incurred by these
configurations with previous work is presented and it was found that the physical model
experiment closely simulated the predicted values. The tests were scaled from actual conditions
in possible marina locations and therefore the performance criteria measured could be applied in
reverse to potential site locations.
From analysis of the physical model results, it was clear that the highest energy loss was found,
in general, to occur with low porosities (below 10%), as could be expected. For a fixed screen
configuration in terms of pile element shape and porosity, the performance is heavily dependent
on wave steepness, the steeper waves incurring a lower transmission coefficient than the less
steep waves. For a given porosity, circular piles performed the best (transmit the least) followed
by square piles and then diagonal square. When comparing the material used, diagonal square
piles yielded better performing breakwaters due to the expanded cross section gained in
elevation.
The work has provided useful insight into the performance of piled row breakwaters in restricting
transmission of wave energy. Design guidance has been provided when considering the
parameters for deriving conceptual layouts for piled row breakwater structures.
Recommendations were put forward for further work in this field, including potential study areas,
data gathering, and study methods, as well as more applied uses of piles, for example in
combination with other elements in a marina. / AFRIKAANSE OPSOMMING: die veilige bewaring van klein vaartuie, hetsy vir ontspanning of kommersiële gebruik, is die
hoofvereiste in die ontwerp van 'n funksionele hawe fasiliteit dat die beskermde hawegebied ‘n
rustende water oppervlak sal moet handhaaf. Golwe wat oorgedra word deur die omtrek
golfbrekers van ‘n hawe deur middel van transmissie veroorsaak oppervlak versteurings in die
hawe bak en dus ook ongewensde versteurings in die vasmeer kondisies. Op ‘n soortgelyke
wyse, veroorsaak golwe wat gereflekteer word vanaf die toegangs kanaal golfbrekers
problematiese kondisies vir die navigeer van bote deur die kanaal.
Die behoefte aan 'n golfbreker alternatief vir die konvensionele oplossing word genoodsaak
wanneer die konvensionele stortrots of caisson golfbrekers nie haalbaar is nie as gevolg van
tegniese of finansiële aspekte (Park et al. 2000). Een van die opsies wat oorweeg kan word as 'n
alternatief is ‘n heipaal-ry tipe breekwater. In breë terme, bestaan dit uit naby gespasieërde
heipale om golf energie te breek, sonder om ‘n ondeurdringbare versperring te vorm. Wanneer
die verskillende opsies vir die skep van 'n heipaal-ry tipe breekwater vergelyk word, kan die
hoeveelheid konstruksie materiaal benodig per opsie die belangrikste vergelykende parameter
word. Die rede hiervoor is die direkte verwantskap aan konstruksie kostes sowel as tyd aspekte
wat gepaardgaan met die konstruksie materiaal hoeveelhede.
Vanuit die literatuurstudie is verskeie verwysings geïdentifiseer waarin vorige teorieë oor
oordrag en refleksie van golwe evalueer word vir wisselende porositeit waardes en intree golf
waardes. Daar is egter 'n beperkte dekking in die literatuur wat ontwerps-riglyne betref.
Byvoorbeeld, die toepaslike omvang van die vorm konfigurasies wat oorweeg moet word
wanneer konsep ontwerp gedoen word, is nie geredelik beskikbaar nie.
Hierdie tesis vergelyk, deur middel van fisiese skaal model toetse, drie heipaal-ry element
vorms, naamlik ronde, vierkantige en diagonal geroteerde vierkante vir verskillende porositeit
waardes oor 'n verskeidenheid van golf inset parameters. 'n Vergelyking is getref tussen die
toetsdata en vorige werk en daar is bevind dat die fisiese model eksperiment die voorspelde
waades uit die literatuur redelik akkuraat kon naboots. Die toets kondisies is geskaal vanaf
werklike moontlike marina terreine en dus kon die toets resultate toegepas word in die ontwerp
van potensiële terreine.
Vanuit die data-analise, is waargeneem dat die hoogste energie verliese oor die algemeen
plaasvind by laer porosititeit waardes (onder 10%) soos wat verwag kon word. Vir 'n gegewe
golfbreker opset, in terme van die heipaal element vorm en porositeit, is die verrigting hoogs
afhanklik van die golf steilheid, met hoër verrigting by steiler golwe. Vir 'n gegewe porositeit, sal
ronde heipaal elemente die beste verrigting gee, gevolg deur vierkante heipale en laastens
diagonal geroteerde vierkante. Vir soortgelyke hoeveelheid heipale, sal diagonal geroteerde
vierkante beter verrigting lewer moontlik as gevolg van die verlengde deursnit dimensie in
vooraansig.
Hierdie navorsing het goeie insig verskaf oor golfdeurlaatbaarheid en weerkaatsing van heipaalry
breekwaters. Ontwerp riglyne word ook verskaf wat betref die parameters wat gebruik kan
word vir die konsep ontwikkelings fase vir heipaal-ry breekwaters.
Aanbevelings word gemaak vir verdere navorsingswerk in hierdie veld, insluitend moontlike
studie-areas, data insameling, studie metodes, sowel as vir meer toegepasde situasies,
byvoorbeeld waar die heipaal elemente in kombinasie met ander marina komponente ontwerp
moet word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/86710 |
| Date | 04 1900 |
| Creators | Gous, Werner |
| Contributors | Toms, Geoff, Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xii, 98 p. : ill. |
| Rights | Stellenbosch University |
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