Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The study reported in this thesis focuses on the development of algorithms that can be used to schedule routine maintenance work in maintenance wards of a gravel road network, This was undertaken as part of the development of the Blading Optimisation Module of the Gravel Management System of the Provincial Government: Western Cape. Two scheduling algorithms were developed and mapped to a pilot object model on the computer. The algorithms and application interface takes account of the constraints and variables of routine maintenance that were identified through interviews with personnel of the five District Municipalities contained in the Western Cape. The algorithms are tested and evaluated using the pilot application. Based on the evaluation of the algorithms conclusions are drawn and recommendations are made. / AFRIKAANSE OPSOMMING: Die studie beskryf in hierdie tesis fokus op die ontwikkeling van algoritmes vir die skedulering van roetine instandhoudingswerk in instandhoudingswyke van 'n gruispadnetwerk. Dit is ondemeem tydens die ontwikkeling van die "Blading Optimisation Module" van die "Gravel Management System" van die Provinsiale Regering: Wes Kaap. Twee algoritmes is ontwikkel en afgebeeld op 'n loods-objekmodel op die rekenaar. Die algoritmes en toepassingskoppelvlak maak voorsiening vir die beperkings en veranderlikes wat geidentifiseer is tydens onderhoude met personeel van die distrikmunisipaliteite in die Wes Kaap. Die algoritmes is getoets en geevalueer met behulp van die loodstoepassing. Gevolgtrekkings en aanbevelings word gemaak op grond van die resultate van die evaluasie van die algoritmes.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Accelerated pavement testing (APT) is the application of a wheel loading, to a prototype or actual layered, structural pavement system to determine pavement response and performance under controlled, accelerated accumulation of damage in a compressed time period. It is a tool used for the evaluation of performance of new pavement materials, distress mechanisms, pavement distress, and selection of rehabilitation strategies. In this study, the research work that was done in Jacksboro, Texas (USA) with the third-scale Model Mobile Load Simulator (MMLS3) as part of the APT programme of the Texas Department of Transportation (TxDOT) is presented. The primary objective was to evaluate the performance ofthe different asphalt concrete (AC) materials (Dustrol and Remixer) used on highway US 281, in terms of rutting and distress due to wet trafficking. The other objective was to investigate the difference in rutting between the MMLS3 and the full-scale Texas Mobile Load Simulator (TxMLS). The scope of the study included fieldwork, laboratory work and theoretical analysis. On average, the performance of the layer from the Dustrol process was found to be poorer than that of the Remixer process. The Dustrol process was more susceptible to moisture damage and less resistant to permanent deformation compared to the Remixer process. The MMLS3 and TxMLS permanent deformations in the upper 90 mm surface layers correlated well in terms of the respective vertical stresses imposed by the two APT devices, after allowing for the difference in environmental conditions during trafficking. Overall, the study demonstrated that the MMLS3, used in conjunction with nondestructive field and laboratory testing, is a significant cost-effective APT device that can be used for evaluating the response and performance of the (surface) layers of full-scale, in-service pavements. / AFRIKAANSE OPSOMMING: Versnelde Plaveisel Toetsing bestaan uit die gebruik van 'n wiellas op 'n prototipe of 'n bestaande gelaagde plaveiselstruktuur om die plaveiselgedrag onder beheerde en versnelde toename in skade in 'n verkorte periode te bepaal. Dit word gebruik om die gedrag van nuwe plaveiselmateriale, swigtingsmeganismes, plaveiselswigting en die keuse van rehabilitasie strategieë te evalueer. Die navorsingswerk met die derde skaal Model Mobile Load Simulator (MMLS3) wat onderneem is in Jacksboro, Texas (VSA), en deel uitmaak van die Versnelde Plaveisel Toetsingsprojek van die Texas Departement van Vervoer (TxDOT), word uiteengesit. Die hoofdoel van die studie was om die gedrag van twee verskillende asfaltmateriale, naamlik Dustrol en Remixer, wat gebruik is op die US 281-snelweg, in terme van sporing en swigting as gevolg van nat belastingstoestande te evalueer. 'n Verdere doelstelling was om die verskil in die gemete sporing tussen die MMLS3 en die volskaal Texas Mobile Load Simulator (TxMLS) te ondersoek. Die studie het veld- en laboratoriumtoetse en teoretiese analise behels. Die gedrag van die Dustrol laag is oor die algemeen swakker as die Remixer lae. Die Dustrol laag, in vergelyking met die Remixer lae, is meer vatbaar vir vogskade en spoor makliker. Nadat die invloed van verskillende omgewingstoestande gedurende asbelasting inaggeneem is, korreleer die sporing vir die MMLS3 en die TxMLS in die lae van die boonste 90mm van die plaveisel goed in terme van die vertikale spannings soos opgewek deur die twee toetstoestelle. In die geheel word bewys dat die MMLS3 tesame met nie-destruktiewe veld- en laboratoriumtoetse 'n belangrike koste-effektiewe versnelde plaveisel toetstoestel is, wat aangewend kan word in die evaluasieproses van die gedrag van (oppervlak) lae van volskaalse plaveisels in gebruik.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The intent of this thesis is to examine the solving of problems with neural networks. Three cases are investigated: the calculation of a Visual Condition Index (VCI), the determination ofthe reseal need, and the back-calculation of E-moduli from measured deflection basins. The calculation of a Visual Condition Index (VCI) is a very good example of how a neural network can be applied to reach a conclusion through the association of a number of facts with one single outcome. VISual assessments of the road condition are done on a yearly basis and the Assessor gives his impression of the condition of a road. A neural network simulates the association between the inputs of elements of distress on the road and the eventual assessment of the overall condition expressed as the VCI, very well. Reseal need is determined by the Provincial Administration: Western Cape (PAWC) with a Reseal Expert System. Data produced by the expert system was used to train a neural network to determine the reseal need. The strength of using these two methods in combination is shown. Meaningful results could not be obtained due to insufficient data in certain categories. Deflection measurements with a Falling Weight Deflectometer are meaningful indicators of pavement strength. Back-calculation is used to calculate E-moduli of pavement layers which can be used in a mechanistic approach to estimate remaining pavement life from pavement response. Conventional backcalculation programs, when implemented in a pavement management system, result in very long computing times due to the large volumes of data available. Neural networks offer the alternative of very fast processing, making the implementation of back-calculation in real-time possible. It is shown that neural networks can back-calculate E-moduli, but with varying degrees of success. The main problem identified is the basis on which the dataset used to train neural networks, is generated using linear elastic theory. The biggest limitation in the linear elastic theory is that non-linear and stress dependent behaviour of materials cannot be simulated, two aspects that have a major influence on the back-calculated E-moduli. Improvements in the data generation process using a theory that accommodates non-linear and stress dependent behaviour of materials may result in improved performance of the neural networks. It is also shown that it is very difficult to design a single neural network that can be successfully used on all the possible pavement types. It is better to identify representative pavement types and train neural networks for each of these. Neural networks can be applied with success in the pavement management field and the combination of Expert Systems, Neural Networks and Fuzzy Logic can be a very powerful method to solve complicated problems. Care should be taken in the design of the neural networks and a good understanding ofthe data is a prerequisite for success. / AFRIKAANSE OPSOMMING: Die bedoeling met die tesis is om die vermoë van neurale netwerke om probleme op te los, te ondersoek. Drie gevalle word beskou: die berekening van 'n Visuele Toestand Indeks (VTI), die bepaling van die herseël behoefte en die terugberekening van die E-moduli vanaf defleksie metings. Die berekening van die VTI demonstreer die vermoë van neurale netwerke om,deur middel van die assosiasie tussen 'n hele aantal veranderlikes tot 'n enkele uitkoms, tot 'n gevolgtrekking te kom. Visuele opnames van paaie word op 'n jaarlikse basis gedoen waar die opnemer sy indrukke gee van die toestand van die pad. In Neurale netwerk simuleer die assosiasie tussen die insette (waargenome gebreke) en die uiteindelike toestands beskrywing van die pad, uitgedruk as die VTI, baie goed. Die Provinsiale Administrase: Wes-Kaap bepaal die jaarlikse herseëlbehoefte met behulp van 'n Herseël Ekspertstelsel. Die uitsette van hierdie stelsel is gebruik om 'n neurale netwerk op te lei om die herseëlbehoefte te bepaal. Die voordele om die twee stelsels saam aan te wend, word getoon. Betekenisvolle resultate kom nie bekom word nie vanweë onvoldoende inligting in sekere kategorieë. Defleksiemetings deur 'n vallende-gewig meetapparaat is betekenisvolle indikators van die plaveiselsterkte. Die E-moduli van die plaveisellae word bepaal deur terugberekenings vanaf defleksiemetings. Hierdie Emoduli kan gebruik word om met behulp van meganistiese metodes die oorblywende leeftyd van 'n plaveisel te bepaal. Konvensionele terugberekenings programme, geïmplementeer in In plaveiselbestuurstelsel, neem lank om die groot hoeveelheid defleksiemetings te verwerk. Neurale netwerke bied die alternatief van die intydse berekening van E-moduli vanweë die besonder hoë berekeningspoed wat behaal word. In hierdie tesis word aangetoon dat neurale netwerke aangewend kan word om die terugberekenigs te doen, maar met 'n wisselende mate van sukses. Die gebruik van die lineêre elastiese teorie om die data vir die neurale netwerke te genereer, word as 'n probleem geïdentifiseer. Die grootste tekortkoming wat met die lineêre elastiese teorie ondervind word is dat dit nie die nie-lineêre en spanningsafhanklike gedrag van materiale voldoende simuleer nie. Beide hierdie twee aspekte het 'n groot invloed op die akkuraatheid van terugberekende E-moduli. Verbeteringe in die generering van data deur 'n teorie te gebruik wat nie-lineêre en spanningsafhanklike gedrag van materiale behoorlik simuleer, mag lei tot 'n beter prestasie van die neurale netwerke. Dit word ook getoon dat dit moeilik is om 'n enkele neurale netwerk te ontwerp wat suksesvol gebruik kan word op alle plaveiseltipes. Dit is beter om verteenwoordigende plaveiseltipes te identifiseer en dan neurale netwerke vir elkeen te ontwerp. Neurale netwerke kan met sukses in die plaveiselbestuur veld toegepas word en die kombinasie van ekspertsteiseis, neurale netwerke en vaagheidstelsels (fuzzy) kan tot kragtige metodes lei om komplekse probleme op te los. Sorg moet aan die dag gelê word met die ontwerp van neurale netwerke en 'n goeie begrip van die data is 'n voorvereiste vir sukses.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Concrete water retaining structures (WRS) in South Africa are under scrutiny due to the numerous durability problems that they have experienced lately; despite the efforts by local and national authorities in conserving these structures. At the heart of these problems are the creep and shrinkage phenomena. While shrinkage is the reduction of concrete volume with time, creep is defined as the time-dependent increase of concrete strain under constant or controlled stress. Both phenomena are affected by conditions to which WRS are exposed hence their accurate prediction is required. Numerical models have been developed to calculate the extent to which concrete creeps or shrinks over time. The objective of this thesis is to identify which of these models is better equipped to be used in South African WRS design. This is achieved through a systematic method that involves an investigation into the contents of these models and a statistical comparison of model calculations to WRS representative data. In partnership with reputable universities, a pioneer experimental creep and shrinkage data base is created in this project from which the WRS related data is selected. While investigating the contents of the numerical models, their applicability to South African WRS is identified and the integrity of model contents is assessed. Indeed, a few irregularities are found in the process and are presented in this thesis. The model calculations are statistically compared to data in the form of individual experiments as well as in the form of groups of experiments with similar concretes to find the ideal prediction model for different types of concretes as well. Also pioneered in this project is a weighted criteria and point system in which the findings of the model content assessment and statistical evaluations are incorporated. It is based on this system that conclusions are drawn and the most suitable prediction model for WRS design in South Africa is selected.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Large areas of the earth’s surface are covered by soils that are susceptible to large decreases in bulk volume when they become saturated. These soils are termed collapsing soils and are very common in parts of the USA, Asia, South America and Southern Africa. This study is concerned with the occurrence of these collapsible soils in the residual granites of the Stellenbosch area. The study was undertaken as relatively little is known about the collapse phenomenon in the problematic weathered granites of the Western Cape. The majority of research thus far has been carried out on the deep residual soils formed on basement-granite in the Transvaal areas, whereas little attention has been paid to the Cape granites. The aim of the study was achieved through the experimental work which included double oedometer testing, indicator analyses and shear strength testing. Double oedometer tests were performed to quantify the potential collapse settlement of the soils from the demarcated study area. To provide a better understanding of the collapse behaviour of the soils, indicator analysis, which included Atterberg limits and particle size distributions, were performed. Direct shear tests were further carried out on saturated and natural moisture content specimens to establish the effect of collapsibility on shear strength and whether substantial additional settlement of the saturated soils would occur during shear. It was found that collapsible soils are prevalent in the demarcated study area as the majority of soils showed a potential collapse settlement of 1% or more. Collapse exceeding 5% were calculated in a few instances proving some soils to be highly collapsible. The double oedometer and indicator analysis results were used in an attempt to obtain a relationship between collapse settlement and a combination of easily determined properties such as dry density (void ratio), moisture content and grading, but no meaningful conclusions have emerged. The shear strength tests indicated that a clear correlation does not exist between collapsibility and shear strength. It was further established that a relationship between collapse settlement determined during the double oedometer testing and the volume change during shear strength testing cannot be assumed. It can thus be concluded that soils can be very unpredictable and further research on the collapse phenomenon is indicated. / AFRIKAANSE OPSOMMING: Groot dele van die aarde se oppervlakte is bedek deur grondtipes wat geneig is tot ‘n afname in volume as dit deurweek word. Hierdie gronde word swigversakkende gronde genoem en dit word algemeen teëgekom in dele van die VSA, Asië, Suid-Amerika en Suider-Afrika. In hierdie studie word die voorkoms van swigversakkende gronde in die residuele graniet in die Stellenbosch area ondersoek. Die studie is onderneem aangesien relatief min i.v.m. die swigversakking-verskynsel in die problematiese verweerde graniet van die Weskaap bekend is. Die meeste van die navorsing sover is onderneem op die diep residuele gronde wat gevorm is op die Argaïese graniet in die Transvaal gebied, en betreklik min aandag is geskenk aan die Kaapse graniet. Tydens die studie is eksperimente wat dubbele oedometer toetse, indikator analises, en skuifsterkte toetse insluit, uitgevoer. Dubbele oedometer toetse is uitgevoer om die potensiële swigversakking van die grond in die afgebakende studiegebied te kwantifiseer. In ‘n poging om die swigversakking-verskynsel van die grond beter te verstaan, is indikator analises wat Atterberg grense en partikel grootte verspreiding insluit, uitgevoer. Direkte skuiftoetse is ook uitgevoer op deurweekte grondmonsters en op monsters wat natuurlike vog bevat, om sodoende die effek van swigversakking op skuifsterkte vas te stel en om uit te vind of aansienlike addisionele sakking van die deurweekte gronde tydens skuif plaasvind. Daar is gevind dat swigversakkende gronde die oorheersende grondtipe in die afgebakende studiegebied is waar meeste van die gronde ‘n potensiële swigversakking van meer as 1% toon. ‘n Swigversakking van meer as 5% is in ‘n paar gevalle bereken, wat bewys dat sommige grondtipes hoogs versakkend is. Die resultate van die dubbele oedometer en indikator analises is gebruik in ‘n poging om te bewys dat daar ‘n verhouding bestaan tussen swigversakking en ‘n kombinasie van kenmerke wat maklik vasgestel kan word soos droë digdheid (ruimte verhouding), voginhoud en gradering, maar daar kon nie tot ‘n sinvolle slotsom gekom word nie. Die skuifsterkte toetse toon dat daar nie ‘n duidelike korrelasie bestaan tussen swigversakking en skuifsterkte nie. Daar is verder vasgestel dat dit nie moontlik is om te aanvaar dat daar ‘n verhouding bestaan tussen swigversakking soos vasgestel tydens die dubbele oedometer toetsing, en die verandering in volume tydens skuifsterkte toetsing nie. Daar is dus tot die slotsom gekom dat grond baie onvoorspelbaar kan wees en dat verdere navorsing na die swigversakking-verskynsel nodig is.

Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: A dam can have a significant impact on the downstream river morphology by altering both the flow regime and the sediment load. The effect of a dam is dependent on factors such as the storage capacity relative to the mean annual runoff (MAR), the operation of the reservoir and the sediment yield of the catchment. Changes in the river morphology include the degradation and coarsening of the riverbed, generally closer to the dam, and aggradation further downstream where the sediment delivered by tributaries cannot be carried through because of the reduced sediment transport capacity of the river. The impact of a dam can stretch over several hundreds of kilometres. The main objective of this thesis was to gain a better understanding of the impacts that dams can have on the downstream river morphology. This was done by developing equations that can describe the channel geometry, investigating the effect of the presence of clay and silt on the sediment transport behaviour of sediments, as well as detailed evaluation of simulations carried out with a one-dimensional mathematical river model (MIKE 11). The calibrated regime equations were found to be comparable to other internationally developed regime equations and to be suitable for natural rivers. It was found, however, that these regime equations are not applicable to rivers downstream of dams that have highly unnatural release patterns. Further research is needed in this regard. By investigating the effect of cohesive sediments on the sediment transport behaviour of mixed sediments it was found that as little as 7% clay and silt in the bed could affect their sediment transport characteristics. A methodology was also developed by which the critical conditions for mass erosion of cohesive sediments can be described in terms of the applied stream power. Sediment transport equations were calibrated and verified in terms of the unit input stream power for fine and non-cohesivesediments. The sediment transport equation for fine sediments was implemented in MIKE 11. The simulations over a 40 km reach of the Pongola River downstream of Pongolapoort Dam, have shown that even when a large demand is placed on the stored water, and most of the smaller floods are therefore absorbed by the dam, the downstream impact can still be considerable, with as much as 5 m deep erosion in places. The sediment loads are generally reduced (by as much as 35%), but the effective catchment area downstream of the dam has been reduced by as much as 90%, indicating that substantial erosion had to have taken place in the river. Coarsening of the riverbed was also observed during the simulations. / AFRIKAANSE OPSOMMING: 'n Dam kan 'n aansienlike impak he op die riviermorfologie stroomaf daarvan, deurdat dit beide die vloei en sedimentlading drasties kan verander. Die effek van 'n dam hang van verskeie faktore af, soos die opgaarkapasiteit in vergelyking met die gemiddelde jaarlikse afloop (GJA), die bestuur van die dam en die sedimentlewering van die opvanggebied. Veranderings in die riviermorfologie behels die degradering van die rivierbed, sowel as die uitspoel van fyn materiaal uit die rivierbed, veral nader aan die dam. Deponering vind verder stroomaf van die dam plaas, waar die sediment wat deur die sytakke ingevoer word nie deurgevoer kan word nie, weens die verlaagde sedimentdravermoe van die rivier. Sodoende kan rivierlope oor honderde kilometers deur 'n dam bemvloed word. Die hoofdoel van die tesis was om meer insig te verkry oor die impak wat damme op die stroomaf riviermorfologie kan he. Derhalwe is vergelykings ontwikkel wat die riviermorfologie kan beskryf. Die effek van die teenwoordigheid van klei en slik op die sedimentvervoer-eienskappe is ondersoek, en gedetaileerde ontledings is met 'n een-dimensionele wiskundige riviermodel (MIKE 11) is gedoen. Daar is bevind dat die regime-formules goed vergelyk met ander intemasionaalontwikkelde formules en dat hulle geskik is vir toepassing op natuurlike riviere. Daar is egter gevind dat die formules nie geskik is vir riviere wat stroomaf Ie van damme wat hoogs onnatuurlike loslatings het nie. Verdere navorsing is op hierdie gebied nodig. Ondersoek na die effek wat klei en slik op die sedimentdravermoe het, het getoon dat slegs 7% klei en slik in die rivierbed die sedimentvervoer-eienskappe van mengsels van fyn en growwe materiaal kan bemvloed. 'n Metode is ontwikkel waarmee die kritiese toestande vir massa-erosie van kohesiewe sediment beskryfkan word in terme van die aangewende stroomdrywing teen die bed. 'n Sedimentvervoer-vergelyking in terme van die eenheids-insetstroomdrywing vir fyn en nie-kohesiewe sedimente is gekalibreer en geverifieer. Die nuwe sedimentvervoer-vergelyking vir fyn sedimente is gebruik in die MIKE 11 simulasies. Hierdie simulasies oor 'n 40 km loop van die Pongolarivier stroomaf van Pongolapoort Dam, het getoon dat selfs as daar 'n groot aanvraag op 'n dam se water geplaas word, en gevolglik meeste van die kleiner vloede deur die dam geabsorbeer word, die impak van die dam nogs steeds aansienlik kan wees, met soveel as 5 m diep uitskuring in plekke. Die sedimentladings het gewoonlik verminder (met soveel as 35%), maar die die effektiewe opvanggebiedarea stroomafvan die dam het met meer as 90% verminder, wat daarop dui dat daar aansienlike erodering in die rivier plaasgevind het. Die simulasies het ook getoon dat die hoeveelheid fyn materiaal in die rivierbed verminder het.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Reinforced concrete is susceptible to cracking. This makes it less durable than it would be had it been crack-free. Ingress of harmful substances into reinforced concrete through cracks – which causes corrosion of steel – is not desirable. This can be mitigated by the use of fibre reinforced-concretes or mortars showing strain hardening properties accompanied by improved ductility and multiple cracking under tensile loading. Such materials are called Strainhardening cementitious composites (SHCC’s). At Stellenbosch University, work has been done in previous years on SHCC to determine its behaviour under various loading conditions. Some of the aspects of the material that have been studied are the behaviour under uni-axial tensile loading, uni-axial compression and shear. The behaviour of SHCC under biaxial stresses was investigated to enable the prediction of the material behaviour under complex stress conditions. Square plate specimens of nominal dimensions 100 x 100 x 20 mm were cast and subjected to biaxial compressive loading at stress path angles of 00, 150, 300 and 450; which were equivalent to vertical/horizontal stress ratios of 0/1, 0.27/1, 0.58/1 and 1/1 respectively, at ages 23 to 33 days. Comparisons were made between specimens tested using steel platens and those tested using Vesconite sheets. Those tested using Vesconite yielded lower failure stresses. Vesconite was used to reduce the retraining effect of the frictional force between the specimens and the steel platens. Poisson’s ratios were calculated for specimens tested using steel and those tested using Vesconite. The values for Vesconite were found to be higher than for steel. Additionally, the values for the uni-axial case were different from those obtained for other stress ratios. This could have been due to the assumption made that plane stress was realised and that Elastic moduli in tension and in compression was the same. The possibility of the existence of a triaxial stress state could render the calculated Poisson’s ratios incorrect. Shear slip type failure accompanied by wedging was observed. Vertical to near diagonal cracks were evident on the front faces of the specimens for the stress path angles of 00 to 450 respectively. The observed crack patterns showed closely spaced multiple micro-cracking on the narrow edges of specimens indicating Strain-hardening behaviour. The stress-strain curves also showed a slight indication of strain-hardening where tensile strains were measured. / AFRIKAANSE OPSOMMING: Gewapende beton is vatbaar vir krake. Dit maak dit minder duursaam as wanneer dit kraak-vry is. Instroming van skadelike stowwe in gewapende beton deur middel van krake - wat korrosie van staal veroorsaak - is nie wenslik nie. Dit kan verbeter word deur die gebruik van veselversterkte beton of mortel wat vervormingsverharding eienskappe toon, vergesel deur verbeterde rekbaarheid en veelvuldige krake onder trekspanning. Sulke materiaal word Strainhardening cementitious composites (SHCC's) genoem. Die Universiteit Stellenbosch, het in vorige jare werk gedoen om SHCC se gedrag te bepaal onder verskillende belastingstoestande. Sommige van die aspekte van die materiaal wat bestudeer is, is gedrag onder uni-aksiale trek, uni-aksiale druk en skuif. Die gedrag van SHCC onder biaksiale spannings is ondersoek om voorspelling van materiaalgedrag onder komplekse spanningstoestande moontlik te maak. Vierkantige plaat monsters van nominale dimensies 100 x 100 x 20 mm is gemaak en aan biaksiale drukkragte onderwerp, met spannningspad hoeke van 00, 150, 300 en 450; wat soortgelyk is aan die horisontale spanning verhoudings van 0/1, 0.27/1, 0.58/1 en 1/1 onderskeidelik, op ouderdomme 23-33 dae. Vergelykings is getref tussen monsters getoets met staal plate en diegene getoets word met Vesconite plate. Die proefstukke getoets met Vesconite het laer falingsspannings opgelewer. Vesconite is gebruik om die uitwerking van die wrywingskrag tussen die monsters en die staal plate te verminder. Poisson se verhouding is bereken vir die staal en Vesconite monsters afsonderlik. Daar is gevind dat die Vesconite waarde hoër was as die vir staal. Daarbenewens het die waardes vir die uni-aksiale geval, verskil van dié vir ander spanningsverhoudings. Dit kan wees as gevolg van die aanname van vlakspanning en dat die Elastiese moduli in druk en in trek dieselfde is. Die moontlikheid van die bestaan van 'n drie-dimensionele spanningstoestand, kan beteken dat die berekende Poisson’s verhoudings onakkuraat is. Skuif-glip tipe faling, vergesel deur vaswigting is waargeneem. Vertikale tot feitlik diagonale krake is duidelik sigbaar op die voorkant van die monsters vir spanningspadhoeke van 0-450 onderskeidelik. Die waargeneemde kraak patrone het nou gespasieerde, veelvuldige mikro-krake op die smal randte van die monsters, wat dui op vervormingsverharding. Die spanningsvervormings kurwes het ook effense aanduidings getoon van die vervormingsverharding waar trekvervorming gemeet is.

Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The use of polymer modified binders have increased drastically over the past twenty years. It is generally accepted that current empirical specification tests do not adequately characterise the improvement in binder properties when bitumen is modified with polymers. At the University of Stellenbosch, a programme was initiated to relate binder properties to asphalt mix performance. This study forms part of that programme. This study focuses on three binders and is an attempt to characterise binder properties fundamentally. The binders that were tested are: • 60/70 penetration grade bitumen • SBS modified 60/70 bitumen • Bitumen-Rubber Two rheometers were used to characterise the binder properties: • Sliding Plate Rheometer (SPR) • Dynamic Shear Rheometer (DSR) The Sliding Plate Rheometer was modified to allow testing at elevated temperatures. The modification is described in this thesis. Three types of testing were used to test the binders: • Creep tests (SPR and DSR) • Dynamic tests (Strain and Frequency Sweeps - DSR) • Flow tests (high temperature viscosity tests - DSR) The results of the tests were used to characterise differences between the binders. Shear susceptibility lines were plotted and viscosities calculated from the creep test results; Master Curves and Black Diagrams were plotted from frequency sweep results; flow test results were used to characterise high temperature behaviour. A further development in the asphalt industry is the move towards the development of performance based specifications. A programme has been initiated in this regard and this study forms part of the programme. As a step towards the development of performance based specifications filler was included in this study. BinderlFiller systems were subjected to the same test programme the binders were, to characterise the influence on binder properties of filler addition. Some of the conclusions that were drawn at the end of the study are: • Polymer modification improves binder properties related to rutting. • Filler addition does not affect binder properties negatively. • Shear rate is very important during production of asphalt mixes and construction of asphalt layers containing polymer modified binders. / AFRIKAANSE OPSOMMING: Die gebruik van polimeer gemodifiseerde bitumen het drasties toegeneem oor die afgelope twintig jaar. Dit word algemeen aanvaar dat die huidige empiriese spesifikasie toetse nie die verbetering in bindmiddeleienskappe van polimeer modifisering aanvaarbaar karakteriseer nie. 'n Program is geïnisieer by die Universiteit van Stellenbosch om 'n verband te vind tussen bindmiddeleienskappe en asfaltmengseleienskappe. Hierdie studie vorm deel van die program. Hierdie werk fokus op drie bindmiddels en is 'n poging om die bindmiddeleienskappe fundamenteel te karakteriseer. Die bindmiddels wat gebruik is in hierdie werk, is: • 60/70 penetrasiegraad bitumen • SBS gemodifiseerde 60/70 bittimen • Bitumen-Rubber Twee reometers is gebruik om bindmiddeleienskappe te karakteriseer: • Glyplaat Reometer (SPR) • Dinamiese SkuifReometer (DSR) Die glyplaat reometer is aangepas om toetse by hoër temperature te doen en die aanpassing wat gemaak is word in die tesis beskryf. Drie tipes toetse is uitgevoer om die bindmiddels mee te toets: • Kruiptoetse (SPR en DSR) • Dinamiese toetse (DSR) • Vloei toetse (DSR) Die resultate van die toetse is gebruik om die verksille tussen die bindmiddels te kwalifiseer. Verskillende grafieke en figure is getrek van die resultate om die onderskeie bindmiddels te karakteriseer. Die beweging weg van empmese spesifikasies na werkverrigting gebaseerde spesifikasies in die asfalt industrie is 'n verder nuwe ontwikkeling. 'n Program is geïnisïeer ten opsigte hiervan en hierdie werk vorm deel van die program. As 'n stap in die ontwikkeling van die werkverrigting gebaseerde spesifikasies is 'n vuIler ingesluit in die toetsprogram. Bindmiddel/vuIler stelsels is onderwerp aan dieselfde toetse waaraan die bindmiddels onderwerp is om die invloed van die vuIler op die bindmiddels te karakteriseer. Sommige van die gevolgtrekkings waartoe gekom is aan die einde van die tesis, is: • Polimeer modifisering verbeter bindmiddeleienskappe met betrekking tot wielsporing. • Die toevoeging van vuIler affekteer nie die bindmiddeleienskappe negatiefnie. • Die vervormingstempo is van groot belang wanneer asfaltmengsels gemeng en lae gebou word van mengsels wat polimeer gemodifiseerde bitumen bevat.

Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: This report deals with the use of Doppler meters to measure flow velocities and hence discharges in streams. The Doppler meter measures the shift in frequency of an acoustic wave, which it emits and then becomes reflected by a moving particle. The reading is converted into a velocity by dividing the shifted frequency by a calibration constant. The particles that reflect the signal need to follow the flow sufficiently closely so that their velocity may be assumed equal to the flow velocity. A previous study on the use of the Doppler meter at a Crump weir (Du Toit and Venter, 1999) indicated that velocities measured with a Doppler meter showed a distinct relationship with recorded water levels. However, the wide scatter of the observed frequencies in this study, necessitated further tests on the use of the Doppler meter at measuring structures as well as calibration tests on the instrument in the hydraulic laboratory of the University of Stellenbosch. The mam objective of this investigation was to establish the relationship between measured Doppler velocities at a Crump weir and the approach velocities in the stream. The instrument was to be tested in both modular and non-modular flow ranges. In addition, the instrument had to be calibrated in the hydraulic laboratory under varying flow conditions, such as very low flow velocities and different sediment concentrations. The placement of the probe at different depths of the flow was also investigated to comment on the accuracy of the Doppler readings at these depths. The results of these tests should serve as guidelines for any additional tests required for use of this instrument in open channel discharge measurements. The Doppler meter used for this study was supplied and manufactured in Stellenbosch by Flotron, and is being marketed as DFM-P-067. It was calibrated in the laboratory in a channel with limited width and hence non-two-dimensional flow conditions. Conclusions were drawn on the calibration constant that was established. The calibration of the instrument requires the division of the cross-sectional flow area into a number of sub-divisions over which the flow was integrated. The calibration constant of 1460 established in this study differs by approximately 6 percent from the theoretical constant value of 1375. The sensitivity of the Doppler meter to different sediment concentrations was also investigated. For the instrument to read a shifted frequency, it is essential that suspended particles that follow the water movement sufficiently closely are present in the stream. It was observed that readings of the instrument in "sediment-free" water differed only by 3.6% from the readings taken in water containing sediments. The instrument was thus not very sensitive to different sediment concentrations. It was also found that the angle at which the probe was placed in the water had no effect on the accuracy of the observed Doppler velocity. It was furthermore found that the Doppler meter worked reliably at all depths, including levels very close to the channel floor and levels just below the water surface. One drawback of the apparatus was the minimum velocity that it can measure accurately. This minimum velocity of 0.046 mis does not compare well with that for other commercially available Doppler meters. The Argonaut-Acoustic Doppler meter for example can measure velocities as low as O.OOOlm/s, meaning that the DFM-P-067 measures a minimum velocity 460 times swifter than the minimum velocity of the Argonaut-Acoustic Doppler meter. After the Doppler meter had been calibrated, it was tested at a Crump weir in the laboratory to determine the relationship between the Doppler velocities, measured at the weir's crest, and the velocities in the approach channel. These tests were performed for both modular and non-modular flow conditions. The report concludes that, within the flow range in which the instrument was tested, there is a linear relationship between the two velocities mentioned. It is likely that the results obtained in the modular flow range can be used to extrapolate for high flows, especially for submergence ratios less than 0.93. The wide scatter of results obtained in the previous study was due to the readings not being averaged. The Doppler meter does not measure a point velocity but an average velocity within the acoustic field that it emits. This acoustic field is very small and depends on the geometry of the probe. Finally it is recommended that the linear relationship in the non-modular flow range be investigated further in a larger model, where the submergence ratio can be better controlled. The Doppler meter should in future also be calibrated in a wide channel in which two-dimensional flow conditions are approached and these results should be compared to the results obtained in this study. Every instrument is expected to have its own calibration constant, and depending on its application, it can either be calibrated at a weir or in the laboratory. The calibration of the instrument at a Crump weir should allow for a wider range of flows, and also very low flow velocities. At the end of this report guidelines were drawn up that are based on the results and conclusions obtained in this investigation. They may serve as an aid for measurements that could be carried out with this instrument in open channels. / AFRIKAANSE OPSOMMING: Hierdie verslag handeloor die gebruik van die Doppler-meter om vloeisnelhede en derhalwe die vloeitempos in riviere te meet. Die Doppler meter word gebruik om die verandering in die frekwensie van 'n akoustiese golf wat deur bewegende deeltjies in die water gereflekteer word te meet. Die lesing word dan omgeskakel in 'n snelheid deur die gewysigde frekwensie deur 'n kalibrasie konstante te deel. Die bewegende deeltjies wat die sein reflekteer, volg die vloei genoegsaam sodat aanvaar kan word dat hulle snelhede gelyk aan die vloeisnelheid is. 'n Vorige studie in die gebruik van die Doppler meter by 'n Crump meetwal het baie belowende resultate getoon deurdat daar gevind is dat die gemete Doppler snelheid 'n duidelike verwantskap toon met veranderings in gemete water vlakke. As gevolg van die wye band in die waargenome frekwensies in die studie is aanbeveel dat verdere toetse op die gebruik van die Doppler meter by meetstasies gedoen moet word. Die instrument moet ook in die laboratorium gekalibreer word. Die hoofdoel van hierdie ondersoek was om die verwantskap tussen die gemete Doppler snelhede by 'n Crump meetwal en die aankomssnelhede in die stroom te bepaal. Dit moes gedoen word in beide die modulêre en niemodulêre vloeibestekke. Behalwe vir die kalibrasie van die instrument in die laboratorium moes die betroubaarheid daarvan onder verskillende vloei toestande ook getoets word, soos byvoorbeeld by lae vloei snelhede en by verskillende sediment konsentrasies. Die instrument is ook op verskillende vlakke binne die vloei getoets om te bepaal of daar op hierdie vlakke betroubare lesings verwag kon word. Resultate verkry, kan dan dien as riglyne vir enige verdere toetse wat nog op die instrument in oop kanale uitgevoer moet word. Die Doppler meter wat vir die ondersoek gebruik is, word in Stellenbosch vervaardig deur Flotron en word onder die naam DFM-P-067 bemark. Dit is in die laboratorium in 'n kanaal met 'n beperkte breedte getoets en IS daarom in nie-twee dimensionele vloei gekalibreer. Gevolgtrekkings IS gebaseer op die kalibrasie konstante verkry uit die toetse. Die kalibrasie van die instrument vereis dat die deursnee area van die vloei in verskeie segmente onderverdeel moes word. Die kalibrasie konstante van 1460 bepaal in hierdie studie verskilongeveer 6% van die teoretiese waarde van 1375 vir die konstante. Die Doppler meter se sensitiwiteit vir verskillende sediment konsentrasies is ook ondersoek. Dit is noodsaaklik dat daar gesuspendeerde deeltjies teenwoordig in die water is en dat die deeltjies saam met die water beweeg om te verseker dat die instrument die gewysigde frekwensie kan registreer. Daar is egter gevind dat die lesings van die instrument in sediment-vrye water slegs met 3,6% verskil van lesings wat in water met sediment geneem is. Dit lei tot die gevolgtrekking dat die instrument nie baie sensitief vir veranderlike sediment konsentrasies in die water is nie. Daar is ook gevind dat die hoek waarteen die sender in die water geplaas word nie die akkuraatheid van die Doppler snelhede beinvloed nie. Verder is gevind dat die Doppler meter bevredigende resultate lewer, ongeag op watter diepte lesings geneem word. Tydens toetse is waarnemings baie nabyaan die kanaal bodem asook nabyaan die water se oppervlak gedoen. 'n Tekortkoming van hierdie instrument is die minimum snelheid wat dit akkuraat kan meet. Daar is gevind dat die Doppler meter se muurnum snelheid lesing van 0.046 mis nie goed vergelyk met dié van ander meters wat kommersieël beskikbaar is nie. Die Argonaut-Acoustic Doppler meter kan byvoorbeeld vloeisnelhede so laag as 0.0001 mis meet wat beteken dat die DFM-P-067 se minimum betroubare vloeisnelheid 460 keer vinniger is as die Argonaut-Acoustic Doppler meter se minimum betroubare vloeisnelheid. Nadat die Doppler meter gekalibreer is, is dit by 'n Crump meetwal in die laboratorium getoets om die verhouding tussen die Doppler snelhede gemeet by die oorloopkruin en die snelhede wat in die aanloopkanaal gemeet is, te bepaal. Hierdie toetse is uitgevoer op beide modulêre en nie-modulêre vloei toestande. Daar is gevind dat daar binne die vloeibestek waarin die toetse plaasgevind het 'n liniêere verband tussen die twee bogenoemde snelhede bestaan. Dit is hoogs waarskynlik dat die resultate wat in die modulêre vloeibestek gevind is gebruik kan word om vir hoë vloeie te ekstrapoleer, veral vir grade van versuiping laer as 0.93. Die vorige studie se uiteenlopende resultate kan toegeskryf word aan lesings waarvan die gemiddelde lesing vir 'n spesifieke vloeitoestand nie bepaal is nie. Die Doppler meter meet nie 'n bepaalde punt-snelheid nie, maar 'n gemiddelde snelheid binne die akoestiese veld wat dit uitstraal. Hierdie akoestiese veld is baie klein en afhanklik van die geometrie van die sender. Ten slotte word aanbeveel dat die lineêre verband in die nie-modulêre vloeibestek in 'n groter model, waar die graad van versuiping makliker beheerbaar is, verder ondersoek moet word. Die Doppler meter moet ook in 'n breë kanaal waarin twee dimensionale vloei voorkom, gekalibreer word. Resultate so verkry moet vergelyk word met die wat in hierdie studie behaal is. Elke instrument behoort sy eie kalibrasie konstante te hê en afhangende van waar dit gebruik word, kan dit of by 'n meetwal of in die laboratorium gekalibreer word. Die kalibrasie van die instrument by 'n Crump meetwal behoort 'n wyer reeks vloeie toe te laat met ook baie lae snelhede. Die verslag word afgesluit met riglyne gebaseer op die resultate en gevolgtrekkings wat uit die ondersoek voortgespruit het. Hierdie riglyne en gevolgtrekkings kan dan dien as 'n hulpmiddel vir metings wat met hierdie instrument in oop kanale uitgevoer word.

Thesis (MScEng)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: With the increased focus on the use of innovative and state-of-the-art technology in Intelligent Transport Systems (ITS), the need for more accurate and more detailed road traffic flow data has become apparent. Data obtained from vehicle detector loops, which merely act as vehicle presence sensors, is neither reliable nor accurate enough anymore. This type of sensor poses the problem that it has to be inserted into the road surface; temporarily obstructing traffic flows, and has to be replaced after pavement reconstruction. One of the solutions to this problem is to develop a traffic surveillance system that uses video image processing. In cities where Intelligent Transport Systems are used extensively, roadways are monitored through Closed Circuit Television Cameras (CCTV) that are closely watched by traffic control centre personnel. These cameras are mounted on posts on the roadside. These cameras can serve a dual purpose, being used for both human monitoring and as inputs to Video Image Processing Systems. In this study some of the digital image processing techniques that could be used in a traffic surveillance system were investigated. This report leads the reader through the various steps in the processing of a scene by a traffic surveillance system based on feature tracking, and discusses the pitfalls and problems that are experienced. The tracker was tested using three image sequences and the results are presented in the final chapter of this report. / AFRIKAANSE OPSOMMING: Met die toenemende fokus op die gebruik van innoverende oplossings en gevorderde tegnologie in Intelligente Vervoerstelsels, het die noodsaaklikheid van akkurater en meer gedetailleerde padverkeer vloeidata duidelik geword. Data wat verkry word d.m.v. voertuig deteksie lusse, wat alleenlik voertuig teenwoordigheid/afwesigheid meet, is nie meer akkuraat of betroubaar genoeg nie. Hierdie tipe sensors het egter die nadeel dat dit in die plaveisel ingesny moet word, dus vloei tydelik kan belemmer, en moet vervang word elke keer as plaveisel rekonstruksie gedoen word. Een van die oplossings vir hierdie probleem is om 'n verkeers waarnemingstelsel te ontwikkel wat van videobeeldverwerking gebruik maak. In stede waar van uitgebreide intelligente verkeerstelsels gebruik gemaak word, word paaie gemonitor d.m.v. geslote baan televisiekameras wat op pale langs die paaie aangebring is. Personeellede van die verkeers beheer sentrum hou dan die inkomende televisiebeelde dop. Hierdie kameras kan 'n dubelle rol vervul deurdat dit vir beide menslike waarneming en as invoer in 'n video-beeldverwerking stelsel gebruik kan word. In hierdie studie was verskeie digitale beeldverwerking tegnieke wat gebruik kan word in 'n verkeers waarnemingstelsel ondersoek. Hierdie verslag lei die leser deur die verskeie stappe in die verwerking van 'n toneel deur 'n verkeers waarneming stelsel wat gebaseer is op die volg van kenmerke. Die verslag beskryf ook die slaggate en probleme wat ondervind word. Die voertuig volger was getoets deur van drie reekse beelde gebruik te maak en die resultate word weergegee in die finale hoodfstuk van hierdie verslag.