The reduction of pile capacity associated with volume contraction of the soil close to the pile surface has been reported in carbonate deposits offshore North West Australia and in residual deposits of Southern Africa. Knowledge of the load carried by the shaft and the pile tip is critical for the determination of the load settlement behavior of piles in structurally unstable and highly variable sand deposits. While the Static and Dynamic formulas and Pile load tests are used for the determination of pile carrying capacity, they are limited in terms of site coverage, cost and adequacy of load settlement data. Since the mode of shearing around a pile shaft is very similar to that observed in the direct shear tests, it is thus cost effective to develop analytical methods based on controlled laboratory model tests in order to predict load settlement behavior and bearing capacity of piles. A simple shear apparatus was developed to investigate whether or not significant contractile strains are induced in low density residual sands subject to simple shear strain and to study the effect of such contractile strain of a soil close to the pile shaft on pile load settlement behavior. The design and development of the simple shear apparatus was based on a new simple shear stress equation. Series of constant normal stresses, constant normal stiffness and constant volume tests were conducted on samples of Berea Sands compacted to low density in the new apparatus, supported by moisture induced collapse settlement and matric suction tests. The tests revealed significant volume contraction of Berea Sands due to imposed simple shear strain. The tests data were fed into a new Winkler - type load transfer model and were used to determine the load - transfer curves of vertically loaded piles. The curves revealed that both the loadsettlement behavior and pile capacity in low density sands are dependent on the volume contraction of the soil in the plastic zone close to the pile surface, horizontal stress normal to the pile shaft and stiffness of the soil outside the plastic zone. / Thesis (Ph.D.)-University of KwaZulu-Natal, 2005.

The continued widespread contamination of the subsurface environment by microbial pathogens and chemical wastes has resulted in an increased interest in the factors that influence microbial transport through porous media. In this work a numerical study is undertaken to determine the influence of various processes that contribute to microbial transport in porous media. The evaluations were conducted by the simulation of a typical macroscopic transport model, using a novel numerical technique referred to as the Green Element Method (GEM). This computational method applies the singular boundary integral theory of the Boundary Element Method (BEM) to a discretised domain in a typical Finite Element Method (FEM) procedure. Three models are presented to evaluate the effects of the various parameters and factors: a constant porosity model was formulated to verify the GEM formulation against an analytical solution, a variable porosity linear model was developed and used for the simulation of the transport process involving first order type clogging, and a variable porosity nonlinear model used to evaluate effects of nonlinear type clogging. All three models were validated by simulations in specific applications in which analytical or deduced solutions were available. The parameters and factors evaluated included the effects of substrate concentrations, decay rates, source concentrations (boundary conditions), flow velocity, clogging rates, dispersivity, point and distributed sources, and nonlinear clogging. The results show that the trends predicted were consistent with the trends expected from theory. The conditions that enhanced bacteria transport included high velocities, low decay rate constants, high substrate concentrations, and low clogging rates. The range of dispersivities investigated showed little variation in the bacteria concentration in the longitudinal direction. Reduction in porosity resulted in retardation of the migrating plume. Conditions that led to significant loss in porosity are high bacteria loadings and high growth rates. The GEM formulation showed no restrictions or limitations in solving transient linear and transient nonlinear applications. In the nonlinear application, the Newton Raphson algorithm was successfully used for the iterative solution procedures. In addition, the GEM formulation easily facilitated the application of distributed and point sources in the problem domain. / Thesis (M.Sc.Eng.)-University of Durban-Westville, 2000.

Studies of community water have been on the increase since the International Drinking Water Supply and Sanitation Decade, 1981 - 1990. However there is some key areas of community water supply that still require research as the literature survey in this thesis illustrates. The Operation and Maintenance of community water supplies has been identified to be as important in sustainability of the services as the institutional factors. Due to the increased number of failure of the community water supplies to continue operation after short periods of time compared to urban water supplies, effort is required to identify the least amount of in puts to ensure continued operation. Through literature survey and field collection of data on management of existing projects a model was developed in order to calculate the minimum amount of funds required for the operation and maintenance. The research showed that the current monthly charges by water committees were sufficient to operate and maintain the systems. The initial calculations using the model also revealed that the current charges would not be sufficient to pay replacement costs. The presence of subsidisation through materials and labour by the central government requires planners to study each project thoroughly before the determination of monthly costs. The conclusion was that further research and data collection was required for the determination of the replacement cost. The model was found to be capable of assisting planners, managers and engineers in the calculation of the cost of operation and maintenance of community water supplies. / Thesis (M.Sc.Eng.)-University of Durban Westville, 2001.

The need to limit sulphur dioxide, nitrous oxides and particulate matter emissions from fossil fuel combustion processes is now a major factor in the design, construction and operation of plants. Over the past 5 to 10 years, most developed countries have introduced legislations to control these. emissions. This report was done to investigate emissions of sulphur dioxide (S02), nitrogen oxides (NOx) and particulate matter from coal fired power plants. S02 emissions contribute to an air pollution load that has been found to be linked to respiratory and heart problems. It increases the formation of acid precipitation, called acid rain. NOx oxides to nitrogen dioxide (N02). N02 acts as an irritant to the respiratory tract, alveoli of the lungs and causes chest pains. Toxic elements concentrate on fine particulate matter because of their high surface-area to volume ratio. These particles penetrate and settle onto the lung wall, leading to respiratory disorders and lung diseases. Due to the strict legislative requirements, flue gas detoxification processes were investigated. They include: • Wet scrubbing • Spray dry scrubbing • Dual-alkali • Well man-Lord • Activated carbon • Magnesium oxides • Selective catalytic recovery • Circulating fluidised bed combustion • Electromembrane desulphurisation A study was done to show the possible cost implications associated with the wet scrubbing, spray dry scrubbing, selective catalytic recovery, circulating fluidised bed and electromembrane desulphurisation process. A variety of methods were used to calculate cost, due to costs being difficult to obtain. Most of the information was based on European, Asian and American installations. The objective of this economic analysis was to compare the different technologies. Because of the assumptions used, costs were always "order of magnitude" estimates. Capital and operating costs were calculated for these technologies, but they can only be used as an indication of costs and to allow for comparisons between the technologies. The costs were converted using the January 2000 exchange rates. Due to this, costs may be more inflated than what would normally be expected due to equipment being purchased earlier than January 2000. Of the processes investigated, the circulating fluidised bed process was found to be the most economical. There is no inexpensive route for the removal of sulphur dioxide, nitrous oxides and particulate matter. The most suitable detoxification process will depend on the legislative requirements per country. South Africa is a signatory of the Montreal Protocol and the Framework for Climatic Change. Legislations for gaseous emissions were not considered a priority. Currently, Eskom's drive is to electrify townships rather than spend money on detoxification processes. However, future legislations may require more stringent control measures. / Thesis (M.Sc.Eng.)-University of Durban-Westville, 2000.

Landfill emissions are the major environmental impact associated with the landfilling of solid wastes. These emissions which are mainly gases and leachate are a result of the anaerobic biochemical breakdown of the waste in landfills. The long term emissions from these solid wastes in landfills can be significantly reduced by Mechanical Biological Pretreatment of the waste prior to landfilling. Mechanical Biological Pretreatment of solid wastes is aimed at reducing the long term polluting potential from landfills through accelerated stabilization of the organic constituent material present in the waste body by biological degradation before the waste is placed in landfills. This research is part of a broader investigation on the applicability of Mechanical Biological Pretreatment of solid wastes prior to disposal in the South Africa Waste Management context. General waste disposed at Bisasar Road Landfill Site in Durban which has been pretreated for 16 weeks in passively aerated windrows was collected and screened using a rotatory drum screen to generate an over-sieved waste fraction with particles of diameter greater than 50mm and an under-sieved waste fraction characterized by particles diameter less than 50mm. The long term behavior of these heavily pretreated wastes was then simulated using large anaerobic reactors (Lysimeter) in relation to grain size distribution. A third lysimeter containing general waste without pretreatment collected from Bisasar Road Landfill Site was also set up in order to study the effect of pretreatment on solid waste samples. The results of this research were then used to make recommendation on the appropriateness of Mechanical Biological in the South Africa Waste Management context. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2007

Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: This thesis covers the factors affecting compactibility of hot mix asphalt including gradation, filler/binder ratios, binder types, binder content, polymer modification, temperature, volumetric properties etc. The study is not limited to compactibility as the property measured, but also on the influence of these factors on the mix’s capacity to resist permanent deformation or rutting. An experimental design was used with a variety of the above factors being included. Laboratory analysis of the mixes as well as accelerated pavement testing of different mix types using the one-third scale Model Mobile Load Simulator (MMLS3) was carried out. The analysis assists in identification of the factors that influence both compactibility and rut resistance, those influencing the one but not the other, and those factors having no significant influence. The compactibility of the mixes has been analysed in terms of voids in the mix at a specific binder content and compaction level. Special consideration was given to the characterisation of the filler and filler/binder system of some mixes. It was found that gradation of a mix has a significant influence on compaction and the rutting performance. High filler/binder ratios were found to be the critical factors influencing the compactibility of the wearing course mixes investigated, but based on the limited tests performed, the reduction of the filler/binder ratios for improved compactibility did not significantly increase rutting under accelerated pavement testing. As expected, the binder type has a significant influence on the rutting resistance as well as compactibility. In addition, an increase in binder content facilitated compaction, but decreased rutting resistance. Polymer modification considerably improved the rutting resistance of a standard mix under the same loading conditions. Although some modifiers may improve rutting resistance, it requires higher compaction temperatures. The addition of the antistripping agent Gripper L decreased the rutting, aggregate stripping and also the rate of rutting of the Quartzite LAMBS mix that result from the stripping failuremechanism. Low densities can lead to considerable rutting and moisture damage, especially when a moisture susceptible aggregate is used. In terms of compactibility as evaluated with the Superpave Gyratory Compactor, it appears that there exists a temperature window in which compaction can be achieved, but in terms of rutting; even a small deviation in temperature can influence rutting results significantly. The control of the temperature during testing is critical if meaningful comparisons between different mixes with regard to rutting performance are to be made. Linear elastic and finite element analysis has been performed to ascertain whether different specimen geometries would influence the stress distribution within the specimen, and subsequently the rutting results. It was found that the geometry of test specimens has an influence on the stress distribution within the specimens, which can influence the permanent deformation results. The briquette specimens tested in the laboratory also yielded higher rutting results for the same mix tested in the field. It is therefore important to use specimens that are most representative of field conditions / AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek die faktore wat ’n invloed het op die kompakteerbaarheid van warm asfalt. Faktore sluit in onder andere gradering, vulstof/bindstof verhouding, tipe bindstof, bindstof inhoud, polimeer modifisering, temperatuuur, volumetriese eienskappe, ens. Hierdie studie is nie net beperk tot kompakteerbaarheid as ‘n gemete eienskap nie, maar ook die invloed van hierdie faktore op die mengsel se vermoë om weerstand te bied teen permanente deformasie of spoorvorming. ’n Eksperimentele ontwerp wat ’n verskeidenheid van bogenoemde faktore insluit is gebruik. Laboratorium analise van die mengsels asook versnelde plaveisel toetse van die verskillende tipe mengsels is gedoen met die een-derde skaal Mobiele Lassimuleerder (MMLS3). Die analise help met die identifikasie van die faktore wat beide kompakteerbaarheid en spoorvorming beïnvloed, asook dié wat slegs die een maar nie die ander beïnvloed, en ook die faktore wat geen beduidende invloed het nie. Die kompakteerbaarheid is geëvalueer in terme van die hol ruimtes in die mengsel by ’n bepaalde bindstof inhoud en verdigtingsgraad. Spesiale aandag is geskenk aan die eienskappe van die vulstof en vulstof/bindstof wisselwerking van die mengsels. Die gradering van ’n mengsel het ’n beduidende invloed op kompakteerbaarheid sowel as spoorvorming. Hoë vulstof/bindstof verhoudings is een van die kritiese faktore wat die kompakteerbaarheid van die betrokke mengsels beïnvloed, maar laer vulstof/bindstof verhoudings vir beter kompaksie het nie ’n beduidende toename in wielsporing teweeg gebring nie. Soos verwag het die tipe bindstof ’n beduidende invloed op kompakteerbaarheid sowel as spoorvorming. ’n Toename in bindstof bevorder verdigting, maar lei tot groter wielsporing. Polimeer modifisering verminder die wielsporing van ’n standard mengsel onder dieselfde beladingstoestand. Alhoewel modifisering wielsporing verminder, vereis dit hoër kompaksie temperature.Die toevoeging van die teenstropingsmiddel GripperL verminder spoorvorming, aggregaat stroping asook die tempo van spoorvorming van die Kwartsiet LAMBS mengsel as gevolg van die stropingsmeganisme. Lae digthede kan lei tot aansienlike vogskade en spoorvorming; veral as die aggregaat vatbaar is vir die invloed van vog. Daar blyk ’n temperatuur interval te wees waarin verdigting met die Superpave Gyratory Compactor bereik kan word; maar selfs ‘n klein temperatuurafwyking kan beduidende invloed op die resultate van spoorvorming hê. Temperatuurbeheer is baie belangrik indien sinvolle vergelykings tussen die sporingsgedrag van verskillende mengsels gemaak moet word. Lineêr elasties en eindige element analise is uitgevoer om te bepaal of verskillende toetskonfigurasies die spanningsverdeling binne die toetsmonsters en die spoorvorming affekteer. Dit is bevind dat die geometrie van toetsmonsters het ’n invloed op die spanningsverdeling in die monsters wat die sporingsresultate kan beïnvloed. Die briketmonsters in die laboratorium gee ook groter spoordiepte teenoor dieselfde mengsel wat in die veld getoets is. Daarom is dit belangrik om verteenwoordigende monsters te gebruik.

Thesis (PhD (Civil Engineering))--University of Stellenbosch, 2007. / The current codes of practice for the design of structures which were studied during this investigation do not explicitly account for the flexibilities and interactions of the Electric Overhead Travelling Crane (EOHTC) and the crane support structure. This leads to analysing the EOHTC and the gantry structure as a decoupled system for ease of computation. Thus, the interaction of the various components of the EOHTC and gantry structure is ignored, which may result in an incorrect assessment of the forces computed in the gantry structure’s members. This led to a study to determine the effects of a EOHTC on the gantry structure. The research was conducted through a series of limited experimental tests and extensive advanced Finite Element Analysis (FEA) simulations. This resulted in developing a computationally efficient FEA model of the full scale experimental EOHTC testing facility in the structural engineering laboratory at Stellenbosch University. The FEA model was developed to conduct simulations for the various load models, namely, vertical wheel load, horizontal longitudinal load and the horizontal lateral load models, as prescribed by the various codes. The research was then focussed at determining the maximum end buffer impact force responses when the crane runs into the end stops. The other load models were investigated by another researcher using the same FEA model. The results from the experimental tests were used to calibrate the FEA simulations. This proved exceptionally challenging due to the various structural response phenomena which occur during the impact of the crane against the end stops. A good correlation between the experimental values and the values predicted by the FEA simulations was achieved for the first impact. Modal analysis and modal superposition methods of analysis were used to determine the effect of the modes of vibration on the structural response to the end buffer impact. A FEA sensitivity analysis was conducted on a set of identified parameters which have a significant effect on the structural response to the end buffer impact. The maximum end buffer impact force was determined for a chosen level of reliability based on the responses from the sensitivity analysis using the Lagrange Multiplier method. These maximum end buffer impact forces are then compared with the forces prescribed by the codes. SABS 0160 slightly underestimates, while SANS 10160 severely overestimates the end buffer impact force obtained from the constraint optimization technique for a target level of reliability of β =3.