Civil Engineering

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A maintenance control system for rural roads.
(1983) Curtayne, Peter C.; Knight, Kenneth.; Fleming, C. J.
No abstract available.
Recycling of bituminous pavement materials.
(1984) Servas, Vladis P.; Knight, Kenneth.; Everitt, Philip Robert.
No abstract available.
Contributions to hydraulic engineering.
(1984) James, William.
No abstract available.
Development of sounding equipment for the assessment of the time- settlement characteristics of recent alluvial deposits when subjected to embankment loads.
(1992) Jones, Geraint Alan.; Knight, Kenneth.
Many embankments on the soft, highly variable, recent alluvial deposits along the South African coast have suffered large settlements necessitating ongoing costly repairs. Due to the soft variable soils, borehole sampling is difficult and laboratory testing requires to be extensive for adequate subsoil modelling; cone penetration testing was considered to be a potential means to overcome these problems. Twenty five years ago in South Africa, as elsewhere, cone penetration testing equipment was relatively crude and the methods of interpretation were simplistic. The application of cone penetration testing to recent alluvial deposits therefore required improvements to both the equipment and the derivation of soil parameters. The equipment was upgraded by introducing strain gauge load cells capable of measuring cone pressures in soft clays with adequate accuracy. Hence, correlations of cone pressures with compressibility and shear strength became possible. Predictions of settlement times and magnitudes are of equal importance and a consolidometer-cone system was developed to assess both of these. A piezometer was incorporated into a cone to ascertain whether the settlements were due to consolidation. The piezometer cone performed so well that it superseded the consolidometer-cone and by 1977 a field piezometer cone was in regular use. Developments in piezocone interpretation have taken place concurrently with those in equipment; coefficients of consolidation are evaluated from pore pressure dissipations, and soils identified from the ratio of pore and cone pressures. These developments have been validated in two recent research projects, by comparing measured and predicted settlements at eleven embankments monitored for up to fifteen years. The data shows that for embankments on the recent alluvial deposits the constrained modulus coefficient, am is : am = 2,6 ± 0,6 The data also shows that coefficients of consolidation from piezometer cone dissipation tests are correlated with those from laboratory tests and back analysed embankment performance as follows : Embankment c = 3 CPTU c = 6 Lab cv It is concluded that piezometer cone penetration testing is particularly suitable for the geotechnical investigation and the subsequent design of embankments on recent alluvial deposits and should be considered as complementary to boreholes with sampling and laboratory testing. The existing database of embankment performance should be expanded with particular emphasis on long term measurements and on thorough initial determination of basic soil parameters
Development of sounding equipment for the assessment of the time- settlement characteristics of recent alluvial deposits when subjected to embankment loads.
(1992) Jones, Geraint Alan.; Knight, Kenneth.
The whole of this thesis is my work unless specifically indicated to the contrary in the text, and has not been submitted in part or in whole to any other University. Some thirty years ago the author operated a deep sounding machine, one of the first in the country, on a misty lake in Ireland and marvelled at the way subsoil information could be garnered. The magic of the moment never entirely passed and when the opportunity arose to use the technique in Natal the die was cast. The development of the national road system surged in the early 1970's and since many of these roads on the Natal coastal routes crossed extensive recent alluvial deposits, the geotechnical problems of instability and settlement became major factors in the road design. Traditional methods of investigation consisted of boreholes with sampling and laboratory testing. Whilst these were satisfactory, provided they were of adequate quality, they were relatively expensive if sufficiently detailed models of the subsoil were to be obtained for design purposes. Cone penetration testing provided a potential a solution and this led to research work conducted over a period of twenty five years which continues today. The initial development of ideas for improvements to the mechanical equipment took place whilst the author was carrying out preliminary investigations for freeway routes over the coastal alluvial deposits. This was followed by a period devoted largely to cone penetration testing research and deVelopment and to embankment design methods at the National Institute for Transport and Road Research, and to the initial registration for a Master's degree under the supervision of Professor K Knight in 1975. This research programme was completed as originally envisaged, but not submitted because during its course the author conceived the idea of the piezometer cone. This proved to be such an exciting prospect that the research and development continued for a number of years until piezometer cone testing has now become almost routine for geotechnical investigations on alluvial deposits. In 1983, due to Professor Knight's retirement from the University, Mr Phillip Everitt was appointed as the supervisor. At that stage piezometer testing was becoming accepted internationally and new aspects and information frequently appeared. It was apparent, however, that the essential proof of the system for the prediction of embankment performance was to use it at embankments where the performance had been monitored. Eventually grants were provided by the Department of Transport for this, which enabled two research projects to be conducted during 1989 - 1990 and 1991 - 1992. After completion of the first of these a presentation of the author's work on cone penetration testing since the mid 1960's was made to the Faculty of Engineering at the University of Natal. The Executive Committee of the University Senate subsequently approved, in August 1991, that the registration be upgraded to doctoral status. Mr Everitt's encouragement during this extended period has been a vital factor in ensuring an outcome for this task and the author wishes to express his gratitude for this.
Traffic circles in South Africa : traffic performance and driver behaviour.
(1997) Krogscheepers, Johann Christoff.; Roebuck, Christopher S.
This thesis presents the results of an investigation into traffic operations and driver behaviour at traffic circles under South African conditions. The scarcity of local traffic circles necessitated the development of a simulation program (TRACSIM) to assist in the research process. This microscopic program for single lane circles is based on event updates and was calibrated and validated based on local data. Because the acceptance of gaps is such a vital part of the operation of a traffic circle, it was examined in detail. Specific attention was given to the possible use of a gap acceptance model based on variables other than time. Since the gap acceptance process also depends on the gap distribution in the circulating stream, the effect of the origin-destination pattern was also investigated. Two existing analysis techniques are evaluated and verified for local conditions, improving them where possible. Generally these techniques under-estimate traffic delay at local circles. Observations indicate a difference between the acceptance of gaps/lags in the entering and circulating stream of conflicting traffic as well as a difference between critical gaps and critical lags. The mean observed critical gaps/lags are larger than in other countries, which indicates that delays at local circles will be greater. Gap/lag acceptance based on critical distances rather than critical times was applied successfully in the simulation program TRACSIM. A method is proposed to estimate critical distances from the geometric layout of the circle. Critical gaps are not fixed, but should vary with at least the conflicting flows. The investigation of the effect of unbalanced flows on delay, showed that the variability in drivers' critical gaps is more a function of delay than of conflicting flow. Entry delays increase because of an increase in conflicting flows or because of an unfavourable imbalance of conflicting flows. In both instances the drivers' critical gaps will decrease. A variable critical gap model only based on conflicting flows will show no change in the drivers' critical gaps if the conflicting volumes remain constant, even though the actual average delay might increase because of an unfavourable imbalance in conflicting flows.
A numerical study of bacteria transport through porous media using the green element method.
(2000) Ramsuroop, Suresh.; Onyejekwe, Okey Oseloka.
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.
The impact of the affirmative procurement policy on affirmable business enterprises in the South African construction industry.
(2000) Gounden, Sivandran Munsami.; Schreiner, Hilson Deneys.; Taylor, Robert Gordon.
The construction industry in South Africa is envisaged to play a pivotal role in the reconstruction of the South African economy, via the delivery of economic and social infrastructure. The skewed ownership I patterns prevalent in the construction sector, resulted in the South African government utilising public sector procurement as a mechanism to address these imbalances, and to promote wider participation I in public sector construction opportunities. This dissertation analyses the role of the construction industry in South Africa, and explores the rationale behind utilising public sector procurement as a mechanism to promote wider participation in the construction industry in South Africa. The research then focuses on the application of the Affirmative Procurement Policy (APP) on construction projects procured by the National Department of Public Works, in order to evaluate the impact which this policy has had on the growth and development of Affirmable Business Enterprises (ABEs). The research evaluates the primary policy outcomes, via the development of appropriate indices and a diagnostic quadrant comparator, and concludes that the application of the APP has had a positive impact on ABE participation, with levels of participation varying across construction sub sectors and categories. It was also found that financial premiums, borne by the State in adopting this policy, were nominal when compared with the initial projected outcomes and the overall benefits. The overall performance of ABEs, measured against that of non-ABEs, was then tested to ascertain whether the adoption of the APP was a necessary and sufficient condition for ABE enablement and empowerment. The research concludes that there is a difference in overall performance between J ABEs and non-ABEs, and that supply side interventions and capacitation programmes are required to mitigate the increased risk exposure by the State, when engaging ABEs on construction projects. The : research also analyses the variation in the levels of participation of ABEs, in the different construction sub sectors and concludes that the manner in which ABEs are structured and their internal business processes tend to establish operational limitations, which influence their scope of activitiies to a larger extent than the existence of eternal sub sector thresholds. Similar characteristics were,observed in non-ABEs of a similar size, inferring that the problems encountered relate to business development and growth of small and medium enterprises, in general. The research also. analyses the impact that the APP has had on subcontracting relationships and the promotion of structured joint ventures. It concludes that whilst the requirements of the APP has seen the development of formalised subcontracting relationships, the form of subcontracts that are currently utilised do not comply with the requirements outlined in the APP, which are aimed at eradicating unfair subcontracting conditions. The adoption of the APP has seen an increase in structured joint ventures between ABEs and larger established contractors. The analysis of these joint ventures concludes that they provide an effective means of transferring expertise, provided that they are structured appropriately. The dissertation concludes with recommendations on APP policy refinements, mechanisms to enhance compliance and opportunities for international application. The recent enactment of the Preferential Procurement Policy Act (Act 5 of 20(0) in South Africa indicates that several elements of the APP are likely to be prescribed as mandatory requirements for public sector procurement by different government institutions and across the different industrial sectors. It is therefore important that the areas identified for further research be pursued, to ensure optimal policy outcomes across a range of industrial sectors.
Rural road maintenance through labour-based lengthmen system in Zambia.
(2000) Mwango, Abraham.; Little, Robert.
Rural road maintenance has received little or no attention in Zambia for a long time, resulting in an adverse impact on the economy. Meanwhile Road Authorities have continued to use traditional capital-intensive periodic and routine maintenance at the expense of scarce foreign exchange. The system has not performed well, hence the current state of roads. Labour-based methods for routine maintenance under the Lengthmen System used in Kenya, Lesotho and other developing countries in the Sub-Saharan Africa have proved to be technically and economically viable. In this report the author examines the desirability of using the Labour-Based Lengthmen System as an alternative to the existing capital -intensive methods in Zambia. This is done through rev iewing rural road maintenance in Zambia and then carrying out a comparative analysis of the same bctween Zambia, Kenya and Lesotho The comparative analysis shows that Zambia is not performing well when compared to Kenya and Lesotho. Meanwhile, the Lengthmen System is more desirable compared to other methods under the current economic conditions. Recommendations, based on the comparative analysis, have been given to improve rural road maintenance in Zambia.
Gaseous and particulate emissions.
(2000) Beebal, Nisha.; Lutchmiah, Johnny Soobramoney.
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.
Costing calculation of operation and maintenance in community water supplies.
(2001) Mwangi, Patrick Nduati.; Otieno, Fredrick Alfred Ochieng.; Ndiritu, John Gatherv.
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.
An assessment of water services in a peri-urban area of Umtata.
(2001) Ntuli, MzwaBantu.; Otieno, Fredrick Alfred Ochieng.
No abstract available.
Ultimate load and deflection behaviour of cellular beams.
(2001) Warren, Juliet.; Dougherty, B.
Cellular beams were developed in 1987 and are an adaptation of castellated beams having many of the same advantages and disadvantages. There are no published results of tests on cellular beams and there is only one recognised method of analysis and design. Full scale destructive tests were carried out for this investigation on eight cellular beams. Beams loaded at midspan and at the third points were tested. Failure load, failure mode and deflections were obtained for each beam. The existing analysis method as well as three new methods for both ultimate load behaviour and deflections were checked against the experimental results. The existing method of analysis was found to be over-conservative in predicting failure loads and inaccurate in predicting deflections. The analysis method which best predicted the failure loads and modes was the design chart which was developed for this investigation. The theoretical method which best predicted the deflection was the Vierendeel method which was also developed for this investigation.
Numerical and experimental study of transient heat transfer through concrete.
(2001) Mabuya, Thabo Gordon.; Onyejekwe, Okey Oseloka.
The increase in temperature of developing concrete as a result of heat liberated by cementing reactions is the primary cause for thermally induced cracks in large concrete elements. It is very essential, in engineering to predict the temperature rises in order to be able to minimise the potential of crack formation. This thesis covers the experimental determination of the heat of hydration curve using the adiabatic calorimeter and experimental determination of transient heat transfer obtained from measurement of temperature variations in concrete at its early ages of hydration. The measured temperature profiles from a one-dimensional heat transfer scenario are then compared with the predicted temperature profiles. The adiabatic hydration curve of a concrete beam sample is used as input into a numerical technique known as the Green Element Method for the calculation of temperature profiles. Time-based boundary conditions are imposed on the equation governing the model and will be solved using the Green Element Method coded in Fortran Power Station 4.0.
A linear catchment model for real time flood forecasting.
(2001) Sinclair, D. S.; Pegram, Geoffrey Guy Sinclair.
A linear reservoir cell model is presented which is proposed as a good candidate for real time flood forecasting applications. The model is designed to be computationally efficient since it should be able to run on a P.C and must operate online in real time. The model parameters and forecasts can be easily updated in order to allow for a more accurate forecast based on real time observations of streamflow and rainfall. The final model, once calibrated, should be able to operate effectively without requiring highly skilled and knowledgeable operators. Thus it is hoped to provide a tool which can be incorporated into an early warning system for mitigation of flood damage, giving water resources managers the extra lead-time to implement any contingency plans which may be neccssary to ensure the safety of people and prevent damage to property. The use of linear models for describing hydrological systems is not new, however the model presented in this thesis departs from previous implementations. A particular departure is the novel method used in the conversion of observed to effective rainlfall. The physical processes that result in the rainfall to runoff conversion are non-linear in nature. Most of the significant non-linearity results from rainfall losses, which occur largely due to evaporation and human extraction. The remaining rainfall is converted to runoff. These losses are particularly significant in the South African climate and in some regions may be as much as 70-90 % of the total observed rainfall. Loss parameters are an integral part of the model formulation and allow for losses to be dealt with directly. Thus, input to the model is observed rainfall and not the "effective" rainfall normally associated with conceptual catchment models. The model is formulated in Finite Difference form similar to an Auto Regressive Moving Average (ARMA) model; it is this formulation which provides the required computational efficiency. The ARMA equation is a discretely coincident form of the State-Space equations that govern the response of an arrangement of linear reservoirs. This results in a functional relationship between the reservoir response constants and the ARMA coefficients, which guarantees stationarity of the ARMA model.
Environmental study of the rehabilitation of the Monze-Zimba Road in Zambia.
(2001) Samu, Silupumbwe Justine.; Joslin, Paul.
It is very unfortunate that despite laws that require adequate incorporation and integration of environmental concerns at all phases of the economic developmental projects in Zambia, the research findings of this dissertation show that they are not applied well. The dissertation consists of six chapters. The Introduction (Chapter One) gives a general overview of Zambia, its geographical position in relation to other African countries, its macro and micro economic policies and its economic needs for a sound transport infrastructure. It also gives a rationale for the Monze-Zimba road rehabilitation project. Chapter Two reviews and states existing policies, legal, strategies and the institutional framework for environmental management and protection in Zambia. It also states and identifies key institutions involved in administering the various environmental laws/regulations and briefly refers to applicable International Conventions. Chapter Three gives a descriptive overview of baseline information - particularly within the catchment area of the road - regarding the biophysical, socioeconomic and cultural environments. The baseline studies provide insights into the normal background environmental variability such that appropriate monitoring programmes can be designed. It is now abundantly and evidently clear that the despoiling of the environment has negative repercussions on the health and wellbeing, culture and economic opportunities of humans. Chapter Four, therefore, provides in-depth discussions of each of the major impacts identified, their nature and scale and appropriate practical measures for their mitigation. The measures are incorporated into an Environmental Management Plan. Chapter Five addresses the environmental monitoring of the impacts resulting from the activities of the road. The Conclusion (Chapter Six) gives substantiated opinions on the overall findings of the research. Recommendations are given to the government of Zambia and all stakeholders on the best ways that environmental issues should be handled at all levels of society.
Turbulent mixing and dispersion in environmental flows.
(2002) Venayagamoorthy, Subhas Karan.; Stretch, Derek Dewey.
Stably stratified flows are common in the environment such as in the atmospheric· boundary layer, the oceans, lakes and estuaries. Understanding mixing and dispersion in these flows is of fundamental importance in applications such as the prediction of pollution dispersion and for weather and climate prediction/models. Mixing efficiency in stratified flows is a measure of the proportion of the turbulent kinetic energy that goes into increasing the potential energy of the fluid by irreversible mixing. This can be important for parameterizing the effects of mixing in stratified flows. In this research, fully resolved direct numerical simulations (DNS) of the Navier-Stokes equations are used to study transient turbulent mixing events. The breaking of internal waves in the atmosphere could be a source of such episodic events in the environment. The simulations have been used to investigate the mixing efficiency (integrated over the duration of the event) as a function of the initial turbulence Richardson number Ri = N2L2/U2, where N is the buoyancy frequency, L is the turbulence length scale, and u is the turbulence velocity scale. Molecular effects on the mixing efficiency have been investigated by varying the Prandtl number Pr = V/K, where v is the viscosity and K is the scalar diffusivity. Comparison of the DNS results with grid turbulence experiments has been carried out. There is broad qualitative agreement between the experimental and DNS results.· However the experiments suggest a maximum mixing efficiency of 6% while our DNS gives values about five times higher. Reasons for this discrepancy are investigated. The mixing efficiency has also been determined using linear theory. It is found that the results obtained for the very stable cases converge on those obtained from DNS suggesting that strongly stratified flows exhibit linear behaviour. Lagrangian analysis of mixing is fundamental in understanding turbulent diffusion and mixing. Dispersion models such as that of Pearson, Puttock & Hunt (1983) are based on a Lagrangian approach. A particle-tracking algorithm (using a cubic spline interpolation scheme following Yeung &Pope, 1988) was developed and incorporated into the DNS code to enable an investigation into the fundamental aspects of mixing and diffusion from a Lagrangian perspective following fluid elements. From the simulations, the ensemble averaged rate of mixing as a function of time indicates clearly that nearly all the mixing in these flows occurs within times of order 3 Vu. The mean square vertical displacement statistics show how the stable stratification severely inhibits the vertical displacement of fluid elements but has no effect on displacements in the transverse direction. This is consistent with the Pearson, Puttock & Hunt model. The important link that asymptotic value of the mean square vertical displacement is a measure of the total irreversible mixing that has occurred in the flow is made. However the results show that the change in density of the fluid elements is only weakly correlated to the density fluctuations during the time when most of the mixing occurs, which contradicts a key modeling assumption of the PPH theory. Improvements to the parameterization of this mixing are investigated. Flow structures in stably stratified turbulence were examined using flow visualization software. The turbulence structure for strong stratification resembles randomly scattered pancakes that are flattened in the horizontal plane. It appears that overturning motions are the main mechanism by which mixing occurs in these flows.
Experimental cadmium contamination of the echinoid Stomopneustes variolaris (Echinodermata: Echinoidea) : influence of dosage and distribution of the metal in the organism.
(2002) Bachoo, Santosh.; Moodley, Ganas Kandasamy.
Cd levels were measured in three different body compartments of the echinoid Stomopneustes variolaris after exposure to concentrations of 5 ug 1l, 20 ug 1l and 50 ug 1l Cd for a period of two weeks. The body compartments investigated included the intestine, gonads and skeleton. The gonads did not exhibit dose-dependent bioaccumulation. The levels of cadmium in the intestine and skeleton were significantly different between the treatments, suggesting that dose dependent bioaccumulation had occurred in these compartments (except in the skeleton where higher levels -were recorded for those exposed to 20 ug 1l than those exposed to 50 ug 1l) The levels recorded in the intestine were higher than those recorded in the gonads and skeleton at the higher Cd exposures of 20 and 50 ug 1i. The levels accumulated in the gonads and skeleton were not significantly different from each other. A separate group, exposed to 20 ug 1`1Cd over a period of two weeks, was placed in uncontaminated seawater to determine if the echinoids were capable of bioremediation. Bioremediation was found to lower the Cd levels in the gonads, but not in the intestine and skeleton. Cadmium levels for the three body compartments were also recorded from specimens collected from the field, indicating the presence of this element in the environment. In addition to using atomic absorption spectroscopy (AAS), energy dispersive X-ray analysis (EDX) was used as a comparative technique to detect the presence of Cd in the skeleton of the urchin. Cadmium was detected in the skeleton with AAS, but not with EDX. S. variolaris proved to be a capable biomonitor of Cd contamination.
Application of digital imaging in measuring cross track drift of vessels entering a port.
(2002) Patel, Sahil Ramesh.; Stretch, Derek Dewey.
Durban is the busiest container port in Africa and there are plans for significant expansion during the next few years. This expansion includes the widening of the port entrance channel to accommodate larger "post-panamax" vessels. Complex crosscurrents near the port entrance, coupled with severe wind and wave conditions, may lead to the intermittent closure of the port which in turn could lead to significant economic implications. Information on the nature of the crosscurrents and how they affect the ships could assist harbour pilots in developing their skills and reduce the risks associated with steering ships into the port. The research involved a case study to develop an innovative new method for directly measuring the effect of wind, waves and crosscurrents on ships entering the port. The technology is based on the application of digital image processing to track the position of ships as they manoeuvre in the port approach channel. The key innovation of this research is the extraction of the heading direction of the ship from the image data. The angle between this heading direction and the true velocity vector (the "crab angle") is then a direct measure of the cross-track drift velocity (CTDV) due to the combined effects of wind, waves and currents. The crosscurrents are usually the main contributing factor to the cross-track drift. The aim of this research was to develop a fully automated image processing system for real-time ship monitoring, and to determine cross-track drift within a wide range of weather conditions and ship parameters. The methodology presented in this research allows the spatial structure of the CTDV along the harbour approach channel to be studied. The relationship of the CTDV to local surface winds was analysed. For deep draught vessels, measured CTDVs were found to be poorly correlated to surface winds. The spatial structure of the measured CTDVs shows distinct regions along the approach channel where vessels experience significantly larger drift velocities. In summary, with the software tools developed by this research, digital images can be captured automatically and analysed to produce ship tracks and crab angles. From this information an extensive database for ship manoeuvring in the approach channel can be developed and the safety and efficiency of port operations improved.
Characterisation and management of landfill emissions under a sub- tropical climate using full-scale landfill cells.
(2002) Bowers, Aiden James.; Trois, Cristina.; Schreiner, Hilson Deneys.
It is now widely understood that landfills, compnslng municipal solid wastes, typically undergo biological degradation processes in what are referred to as Bio-Reactor Landfills. These microbiological processes cause the release of gaseous and liquid emissions, which are commonly called landfill gas (LFG) and landfillleachate respectively. They are formed through mass transfer and biodegradation processes, which occur between percolating water and the solid waste matrix. Such emissions, if not correctly managed, may pose a threat to the natural environment surrounding landfills, and, specifically, landfill leachate may cause significant pollution of the ground water regime. The changes that landfilled wastes undergo to achieve a relatively stable, methanogenic state of decompQsition are now well understood, however little is known on the rate at which biodegradation processes take place, and particularly the timescale over which degradation of waste materials is completed. This dissertation presents research work demonstrating the behaviour of landfill emissions under specific climatic conditions encountered in South Africa in three containment landfill cells situated within the Bisasar Road and Mariannhill Landfill Sites. The containment cells, which are equipped with leachate extraction systems, proved to be ideal full-scale 'pilot plants' where changes in leachate and biogas emissions could be monitored. The characterisation of the landfill emissions allowed for the qualitative determination of the time-scales involved in reaching methanogenic conditions under a sub-tropical climate. Using this information, two landfill gas production models (adapted for the prevalent climatic conditions) were applied to two containment cells in order to predict the volume and duration of gas emissions. The results of the emissions characterisation show that the management of landfill developments in the form of small cells within the larger landfill footprint ('cellular' landfilling) can enhance waste degradation processes, and hence achieve desired levels of stabilised waste conditions relatively quickly. The results of the landfill gas models show that relatively large volumes of gas are emitted early in the lifetime of a landfill cell, and that the maximum emissions will be produced within a relatively short period of time (six to twelve months) after the last deposition of waste. This would allow for the extraction and treatment of landfill gas almost immediately after the closure of a cell, thereby shortening the time span over which potentially harmful emissions can occur.

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