Doctoral Degrees (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 The piezometer cone performed so well that it superseded the consolidometer-cone and by 1977 a field piezometer cone was in regular use.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.
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.
Urban poverty reduction through municipal solid waste management (MSWM) : a case study of Maseru and Maputsoe in Lesotho.
(2002) Mvuma, Godfrey Ganizani Kwantha.; Otieno, Fredrick Alfred Ochieng.
The study was designed to generate data and information necessary for designing an appropriate sustainable solid waste management system, and examining the socio-economic benefits of urban municipal so lid waste management through job creation opportunities (albeit mainly informal) in Lesotho. The review of literature on the integrated solid waste management systems at international, regional and local levels in relation to job creation was carried out with a view to establish the necessity of carrying out this research. In addition, specific solid waste management experiences and practices in other countries have been cited. In Lesotho, investors and donors have, for long expressed the need for formulation of solid waste management policy and guidelines formulated in the country in order to create an enabling environment for investment. However, the process of preparing policy and guidelines requires substantial data and information. This study supplemented this effort by gathering data and information. The data and information gathered were on the existing policies and regulatory framework concerning waste management; waste generation rates, types and quantity from domestic, industrial and commercial establishments; recycling activities; and the waste harvesting (scavenging) activities. The study was undertaken in Maseru and Maputsoe, being the hub of commercial and industrial activities in the country. The data and information may also be useful to other SADC countries From the results of the study, it has been concluded that in Lesotho, paper was the most commonly generated waste in all the categories: domestic, industrial and commercial establishments. Plastic was the second category of the most commonly generated waste, which was followed by organic waste, and then, beverage cans. The study established that the weighted average household generation rate for the surveyed areas was: 0.13 Kg per capita day-I. In the same findings, it occurred that overall, households contribution to waste generation in the surveyed areas ranked second to commercial establishments despite their low per capita, in comparison with industrial establishments. The study has further concluded that out of an estimated total quantity of 157552 tonnes per annum of waste generated in Maseru, commercial establishments contributed 82%, while households contribute 15% and industrial establishments 3%. Households generated more waste than industries because they were in large numbers and hence contributed more than fewer industries. It has also been established that the household waste generation is dependent on incomes ofthese households, but had poor relationship with regard to the number of persons per household. To this effect, it was seen that high-income households generated more waste than low-income. The study further showed that where the municipal council offered waste collection service, not all recipients paid for this service. However, there was a general willingness- to- pay for the waste collection service by all sectors, on condition that there was an improvement in the offering of this service; and if made available where currently not offered. Furthermore, there was a general indication of affordability for these services up to a certain amount (albeit minimal) per different sectors. On the other hand, the information collected strongly indicated the need to invest more in solid waste management if this would be a means of employment creation and improvement of the environment. On the overall, the study revealed that there was a low level of awareness on waste related policy and regulatory instruments, and fragmented legal framework on waste management in Lesotho. The study also established that currently, solid waste as an informal sector generated an estimated profit of MO.7rnillion per annum from waste recycling related activities and that this informal sector generated about 282 jobs. In addition to these benefits, the question of solid waste as a source of biomass energy was another beneficial route in Lesotho. It has been established that the combustible organic waste was highly sought after as a source of energy for cooking and heating. However, besides the benefits, these activities also gave rise to some adverse impacts. The waste harvesters expressed that their health had been negatively impacted upon by the waste scavenging activities. Needless to suggest that there would be a need by the government to intervene in this problem by formalising these waste harvesting activities. It is hoped that this study would serve as a reservoiur for the source of data and information and for Lesotho and that other countries in the SADC Region shall fmd this document a useful tool.
High resolution space-time modelling of rainfall : the string of beads model.
(2003) Clothier, Antony Neil.; Pegram, Geoffrey Guy Sinclair.
The purpose of this study was to develop a rainfall model, continuous in space-time, which captures both the spatial and temporal structure of rainfall over a range of scales varying from lkm to 128km pixels at temporal resolutions ranging from 5 minute up to 1 year. Such a model could find application in a variety of hydrological fields including the management of flash flood scenarios where it could be used in combination with runoff models as a training tool in the operation of flood control structures, the assessment of flood risk, the management of water resources in an area through the simulation of long rainfall sequences and as a short term rainfall forecasting tool, to name a few. The String of Beads Model (SBM) is a high-resolution space-time model of radar rainfall images. It is a stochastic model that takes advantage of the detailed spatial and temporal information captured by weather radar and combines it with the long term seasonal variation captured by a network of daily raingauges. The alternating wet-dry process, or event arrival and duration, is modelled as a one dimensional process, while the detailed wet process is modelled as a three-dimensional (two space and one time) process at 1km, 5 minute spatial and temporal resolutions respectively, over an area of 16000km2, consistent with the observed radar data. The three-dimensional rainfall events distributed on a one-dimensional time line, is analogous to a "String of Beads". The SBM makes use of a combination of power law numerical filtering techniques and well-known time series models to achieve an efficient algorithm that can be run on an ordinary personal computer. Model output is in the form of image files which, when viewed as an animated sequence, are difficult to distinguish from observed radar rainfall images. Apart from the realistic appearance of these images, when calibrated to daily raingauge data for the region, analysis of the simulated sequences over periods of up to ten years, reveal convincing rainfall statistics for a wide range of spatial and temporal scales. It can be used both as a simulation tool and as a short term forecasting tool. In simulation mode, it can quickly produce long sequences (tens of years) of 128 x 128 km rainfall images at five minute, one kilometre resolution. Such simulations can be used as input to distributed and semi-distributed hydrological models to produce "what if" scenarios for applications in water resources management and flood risk assessment amongst others. In forecasting mode, the SBM has proved effective in producing real time forecasts of up to two hours making it a useful tool for flood warning and management, particularly in steep or urban catchments which react quickly and often give rise to flash floods. It can also be used in a combined simulation-forecasting mode to quickly produce many short term "what if" scenarios which can be used to assess the risk of possible growth or decay scenarios in real time.
A study on sustainable waste disposal in South Africa using mechanical biological waste treatment.
(2009) Griffith, Mark Richard.; Trois, Cristina.
The landfilling of Municipal Solid Waste poses a threat to the environment in the form of landfill emissions. These emissions are a result of the biochemical breakdown of the waste in the anaerobic landfill environment. A solution to this problem has been found in the form of the mechanical-biological treatment of waste. This technology involves mechanical and biological processing of the waste before it is placed in the landfill. The pretreatment accelerates the degradation of the waste resulting in the landfilling of a more biologically stable product, resulting in a reduction of the emission potential of the landfill. This research aims at investigating the applicability and efficiency of a passively ventilated MBT windrow system under a sub-tropical climate. The research was conducted in two stages: the first stage focused on the implementation and analysis of the Mechanical Biological Treatment (MBT) process with aerobic windrows, employing the Dome Aeration Technology (OAT) (Mollekopf et al. 2002). Three OAT windrows were constructed at the Bisasar Road Landfill in Durban in order to study the efficiency of the process after different composting timeframes (8 and 20 weeks). The study proved that the use of the OAT technology is a viable option. The second stage was the analysis of this treated waste in an anaerobic environment, in order to simulate landfill conditions and, thus gain insight into the effect of MBP on landfill emissions. Six Iysimeters and 5 columns as well as numerous eluate tests were conducted in order to study the "post-Iandfilled" behaviour of the waste and the effect that waste treatment, composting time and screening have on liquid and gaseous emissions. A basic cost estimate using the Clean Development Mechanism for financial assistance was conducted. The results of this research were then utilised to make recommendations on sustainable waste disposal options. The findings of the research were that although the MBT did not reduce emission levels sufficiently to allow for a 40 year landfill aftercare period, the benefit over the landfilling of untreated waste is significant.
Towards a zero waste South Africa : a case study on post-consumer solid waste management in rural and urban areas.
(2009) Matete, Ntlibi O.
Through the National Environmental Management Act (No. 107 of 1998), the South African Department of Environmental Affairs and Tourism (DEAT) introduced the concept of the Waste Hierarchy (Reduce - Reuse - Recover - Dispose) as the only possible road towards sustainable development. This concept of sustainable waste management was extended into the Polokwane Declaration on Waste Management which identified Zero Waste as the ultimate goal for sustainable waste management systems in South Africa. Zero Waste is defined as the concept of using all waste produced in a certain area for production activities in that area when it is environmentally acceptable, socially equitable and economically viable, with unavoidable residual waste going to landfill. The aim of this thesis is to test the applicability of Zero Waste to post-consumer waste arising from rural and urban areas. The primary reason that this study has been attempted is that little research in South Africa has focused on the demand-side management of post-consumer waste, and that whatever research that has been undertaken has focused almost exclusively on waste management in urban areas. In order to realise the aim of this thesis, two case studies were selected and analysed: one rural and one urban. These case studies were selected due to differences in characteristics of the waste arising from households, existing waste management systems and socio-economic indicators for households in these areas. In each case study, a proposed Zero Waste Scheme was assessed for application based on four sustainability criteria: environmental, social, economical and institutional. The Zero Waste Schemes are based on the conceptual Zero Waste Model (ZWM) that has been specifically developed as the main tool for conducting this research. The development and use of the ZWM in assessing waste management systems in South Africa is a significant contribution of this thesis to knowledge. Generally, the results showed that the proposed Zero Waste Schemes could meet three of the evaluation criteria used in the investigation, but could not meet the fourth: institutional sustainability. For this reason, the Zero Waste Schemes could not be implemented since the municipalities responsible for waste management in those areas did not have the capacity administrative, financial resources and political will - to implement them. Thus, institutional sustainability has been shown to be the main constraint in the application of Zero Waste Schemes in post-consumer waste management systems in South Africa. This is another significant contribution of this thesis to knowledge.Other significant findings from this study reveal that rural areas lack basic waste collection and disposal systems; hence this lack in service delivery prevents full implementation of Zero Waste Schemes in these areas. In contrast, households in urban areas are served by integrated waste management systems that extend to most households, and most of these households are able to finance the waste management services provided. The existence of the integrated waste management systems was used as a basis for introducing waste minimisation and at-source separation of recyclables in order to reduce the amount of waste needing disposal. Education of households in urban areas has been identified as a key factor in establishing Zero Waste Schemes in the case study areas. In conclusion, it has been shown in this thesis that although Zero Waste Schemes are theoretically applicable to rural and urban areas of South Africa, institutional constraints that will have to be overcome in order to make Zero Waste a reality. Implicit in this conclusion is the extension of waste collection services to rural households and the full participation of rural and urban households in Zero Waste Schemes, participation which can only be verified by actual implementation of the schemes. This is the next step in the approach towards Zero Waste within post-consumer waste management in South Africa.
The role of waste data in changing behaviour : the case of the South African waste information system (SAWIS)
(2011) Godfrey, Linda Keren.; Scott, Dianne.; Trois, Cristina.
The South African waste information system (SAWIS) developed and implemented by the Department of Environmental Affairs in 2006, provided a unique case study to explore the research question “Can the collection of data for a national waste information system change the way waste is managed in South Africa, such that there is a noticeable improvement?” The research adopted an inductive approach, incrementally constructing a conceptual model of the knowledgeable, situated waste actor, through observation and hypothesis-building and -testing. The thesis draws on theory from the fields of environmental information disclosure, science communication, environmental education, and environmental psychology, in an effort to understand and contextualise the influence of waste data and knowledge on waste behaviour. Two empirical studies were undertaken in 2006 and 2011. The studies explored whether SAWIS could create opportunities beyond simply being a tool for data collection, by building the waste knowledge of those persons tasked with the responsibility of collecting and reporting the data. The thesis posited that this new knowledge could lead to changes in personal behaviour and ultimately changes in the way organisations manage their waste. While Miller & Morris’ (1999) theoretical framework of learning provided a useful means of interpreting the 2006 data, the results showed the theoretical framework to be overly simplistic for understanding the role of waste data in a developing country context such as South Africa, in that it did not account for all of the evidence gathered, particularly the existence of behavioural and situational influences. The preliminary theoretical framework was expanded in the 2011 empirical study by including Ajzen’s (1985) theory of planned behaviour. Situated within a pragmatic paradigm, the research adopted a mixed-methods research approach, making use of both quantitative and qualitative methods. The results showed that of the three constructs of knowledge (experience, data, and theory), experience currently has the greatest influence on building waste knowledge, nearly twice that of data/information and three times that of theory. Together the three variables (experience, data, and theory) account for 54.1% of the variance in waste knowledge. Knowledge is shown to have a significant influence on all three of the antecedents to behavioural intention – attitude, subjective norm and perceived behavioural control. Furthermore, perceived behavioural control, and not intention, has the greatest influence on waste behaviour, with the model accounting for 53.7% of the variance in behaviour. Respondents from public and private waste organisations represent two distinct sub-groups in the data set, subject to significantly different influences and behaviours, creating two local models. The theoretical framework accounts for 47.8% of the variance in behaviour in the municipal local model, and 57.6% of the variance in behaviour in the private local model. By applying the combined learning-behaviour theories, the results showed that there are only three regressors that currently have a significant effect on waste behaviour, viz experience, knowledge and perceived behavioural control. Two important conclusions were reached by combining the learning-behaviour theories. First, that there are obstacles that hinder the translation of intention into behaviour in the South African context, which suggests that good waste management practice is not always under the volitional control of those tasked with its implementation. Second, that there are significant differences in the way waste knowledge and behaviour are constructed, which suggest that there are underlying social forces that shape waste behaviour and that these forces may be different in public and private waste organisations. Recognising the influence of both societal structures and agency, the theoretical framework was further expanded by embedding the two linear learning-behaviour theories within Giddens’ (1984) theory of structuration. The conceptual model of the knowledgeable, situated actor developed through this research, provides a means of understanding these barriers to action and the societal context within which waste management takes place in South Africa. From the results it is clear that a tension exists between the national neo-liberal, capitalist economic structures which support a pro-growth paradigm, and the political structures which support a pro-poor social paradigm. Furthermore, this tension plays out within a country undergoing political and organisational transformation post-1994. These structures directly influence the way waste is managed. This research proposes that by understanding the way in which knowledge and behaviour are constructed, and the societal context within which this takes place, it is possible to identify practical interventions that will lead to an improvement in the way waste is managed in South Africa.
Capacity of vertically loaded piles in low density sands.
(2011-05-26) Okonta, Felix Ndubisi.; Schreiner, Hilson Deneys.
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.
A new approach to the polyaxial stress numerical analysis of underground openings.
(2012) Scussel, Dario.; Chandra, Sarvesh.; Trois, Cristina.
The traditional design methodologies for tunnel and underground excavations are divided in to three categories: Empirical, Analytical, and Observational approaches, whereas in the last years the Numerical approach has strongly become popular both for the intrinsic simplicity of the software packages and their ability to manage problems unsolvable with the classic methods. In this thesis, the underground openings have been analyzed using constitutive models other than the Mohr-Coulomb theory. FLAC is used for the analysis and the software has been implemented to include the Polyaxial Strength Criterion. The details of the modifications made in the software are presented and the results are compared with the Singh's elasto-plastic stress distribution in squeezing grounds. The applicability of the Polyaxial Strength Criterion has been therefore extended to all the numerical suites designed for geo-mechanical purposes (FEM, FDM, …) and the obtained results compared to the observations of deformation and radial squeezing pressure of the instrumented tunnels in the Chibro-Khodri underground power station. This study will develop better comprehension of the behavior of the underground openings and also provide a useful tool to the designers in the planning stages.
Predicting shoreline response to wave and sea level trends.
(2012) Corbella, Stefano.; Stretch, Derek Dewey.
In March 2007 the KwaZulu-Natal coastline was devastated by an extreme storm event. There is international concern that such events are associated with climate change. There is evidence of global changes in climate but there is still uncertainty as to whether they are anthropogenic or part of natural decadal (or longer) cycles. The increase in frequency and intensity of extreme storm events will impact on the sediment dynamics of coastlines and the associated risks need to be modelled and quantifed so that they can be included in coastal planning and management. Durban is a coastal city on the east coast of South Africa and has been used as a case study to identify trends in wave parameters and beach profile volumes. The correlation between profile erosion, waves and tides was explored using singular spectral analysis. The dependence between wave parameters was modelled using copulas. The decadal trends were introduced into these models using a nonstationary generalised extreme value distribution. Numerical models (SWAN, SBEACH, XBEACH) were used to transform the statistical model to near shore waves and estimate the associated erosion. The copula model was used to investigate the relationship between multivariate return periods and erosion return periods. Coastal defence options were reviewed and those appropriate for Durban were identifed. This study provides a review of Durban and Richards Bay's 18 years of Waverider data. It presents wave parameter exceedance statistics and wave height return periods for Durban. Durban's wave data showed increasing trends in maximum significant wave heights, peak wave period, storm event frequencies and a trend towards a more southerly mean wave direction. However, only the increase in peak period and wave direction was statistically significant. The trend in wave direction is considered a potential coastal hazard as it has the potential to increase the littoral drift by 1 % per annum. Durban's beach profiles have shown a long term erosion trend which is due to a combination of wave and sea level trends, and a reduction in sediment supply. The reduction in sediment supply from rivers was found to be both anthropogenic and natural. Storm, wave parameter and sea level trends were estimated to contribute more than 75 % to the total long term erosion. It was found that it takes an average of 2 years for a beach to recover to its pre-storm volume. Different types of coastlines recover at different rates and these recovery rates should be considered in risk assessments. A method for estimating future impacts due to storm and sea level trends has been proposed in the form of a non-stationary copula based statistical model. In general a bivariate return period of wave height and duration was found to approximate erosion return periods, while a method for estimating an analogous multivariate storm and erosion return period was developed. Geotextile sand filled containers were found to be a suitable coastal defence as they satisfy social, environmental and political pressure.
An investigation into the emissions of greenhouse gases associated with the disposal of solid waste in the eThekwini Municipality.
(2013) Friedrich, Elena.; Trois, Cristina.
The amount of greenhouse gases (GHG) emitted due to waste management in the cities of developing countries is predicted to rise considerably in the near future; however, these countries have a series of problems in accounting and reporting these gases. This study investigated GHG emissions from the municipal waste sector in South Africa. In particular, the eThekwini Municipality is researched in detail and current emissions as well as further projections have been calculated. This research has to be placed in the wider context where developing countries (including South Africa) do not have binding emission reduction targets, but many of them publish different greenhouse gas emissions data which have been accounted and reported in different ways. Results from the first stages of this research showed that for South Africa, inventories at national and municipal level are the most important tools in the process of accounting and reporting greenhouse gases from waste. However, discrepancies in the methodology used are a concern. This is a challenging issue for developing countries, especially African ones, since higher accuracy methods are more data intensive. Therefore, the development of local emission factors for the different waste management processes is important as it encourages a common, unified approach. In the accounting of GHG from waste at municipal level, emission factors, based on a life cycle approach, are used with increased frequency. However, these factors have been calculated for many developed countries of the Northern Hemisphere and are generally lacking for developing countries. The second part of this research showed how such factors have been developed for waste processes used in this country. For the collection and transport of municipal waste in South Africa, the average diesel consumption is around 5 dm3 (litres) per tonne of wet waste and the associated GHG emissions are about 15 kg CO2 equivalents (CO2 e). Depending on the type of landfill, the GHG emissions from the landfilling of waste have been calculated to range from -145 to 1 016 kg CO2 e per tonne of wet waste, when taking into account carbon storage, and from 441 to 2 532 kg CO2 e per tonne of wet waste, when carbon storage is left out. The highest emission factor per unit of wet waste is for landfill sites without landfill gas collection and these are the dominant waste disposal facilities in South Africa. The emission factors developed for the different recyclables in the country showed savings varying from -290 kg CO2 e (glass) to – 19 111 kg CO2 e (metals - Al) per tonne of recyclable. They also illustrated that there is variability, with energy intensive materials like metals having higher GHG savings in South Africa as compared to other countries. This study also showed that composting of garden waste is a net GHG emitter, releasing 172 and 186 kg CO2 e per tonne of wet garden waste for aerated dome composting and turned windrow composting, respectively. By using the emission factors developed, the GHG emissions from municipal waste in the eThekwini Municipality were calculated and showed that for the year 2012 net savings of -161 780 tonnes CO2 e were achieved. This is mainly due to the landfill gas to electricity clean development mechanism (CDM) projects and due to recycling in the municipality. In the absence of landfill gas (LFG) collection and utilisation systems, which is typical for the majority of South African landfills, important GHG emission from the anaerobic degradation of waste are recorded. In the near future (year 2014) the closure of one of the three local landfill sites and the re-directioning of the majority of waste to another landfill sites which does not have LFG collection and utilisation, will cause an increase of GHG emissions to 294 670 tonnes CO2 e. An increase in recycling and the introduction of anaerobic digestion and composting has the potential to reduce these emissions as shown for the year 2020. However, only the introduction of a LFG to electricity system will result in the highest possible overall GHG savings from waste management in the municipality. In the absence of the Clean Development Mechanism and the associated financial arrangements, these systems have to be financed locally and might present a financial challenge to the municipality. Therefore, the second intervention which will make a difference by lowering GHG emissions from waste management would be to increase recycling in general and in particular the recycling of paper and metals. Since there is no direct competition for carbon, in addition to recycling, anaerobic digestion can be introduced and this combination will achieve increased savings in the future. If anaerobic digestion is not possible, composting in addition to recycling will also lead to savings, albeit not as high as with anaerobic digestion. The results presented in this study show that life cycle based GHG emission factors for waste and their use can support a unified approach to accounting of GHG and better decision-making for municipalities in the local context. They can give valuable input for the planning and development of future waste management strategies and they can help optimise current municipal solid waste management.
Effective HIV and AIDS management : a South African construction sector model.
(2013) Harinarain, Nishani.; Haupt, Theodore Conrad.
Abstract available on PDF file.
Anthropogenic impacts and biophysical interactions in Lake St Lucia.
(2013) Chrystal, Robynne Angela Lawrie.; Stretch, Derek Dewey.
The St Lucia estuarine lake system in South Africa is part of a UN- ESCO World Heritage site and a Ramsar wetland of international importance. Like many estuarine systems worldwide St Lucia has experienced signi cant anthropogenic impacts over the past century including catchment land use changes, water diversions/abstractions and inlet manipulation. In addition, the system has recently su ered losses in species diversity and abundance following unprecedented hy- persaline conditions and desiccation. Questions regarding its sustain- ability have motivated a reevaluation of management decisions made in the past and of options for the future. To understand the func- tioning of the system, it is necessary to analyse it holistically in terms of the physical processes and their interaction with the biology. This study focusses on aspects of the biophysical interactions in the estu- arine complex, and aims to provide new knowledge to underpin the development of improved models for predicting the response of the system to anthropogenic interventions. A model for the water and salt budgets was used to investigate what if scenarios in terms of past anthropogenic interventions, in particular the e ects of diverting the Mfolozi River from St Lucia. Furthermore, the risks of hypersalinity and desiccation were assessed for each sce- nario. Integrating these modeled scenarios with observed biological responses to physicochemical changes suggested that large long-term changes in the ecological structure can be expected in the di erent management scenarios. To validate this, the ecosystem response to changing environmental responses was quantitatively assessed using ecological network analysis. Long-term simulations show that the separation of the Mfolozi and St Lucia mouths had a signi cant impact on the functioning of the St Lucia system. The Mfolozi plays a pivotal role in maintaining a more stable mouth state regime and provides a vital source of freshwater during dry conditions. The con guration of the Mfolozi/St Lucia inlet plays a key role in the physico-chemical environment of the system and in uences the system's susceptibility to desiccation and hypersaline conditions. Ecosystem indices revealed that the water level, salinity and mouth state have a signi cant impact on species abundance and diversity as well as the ecological structure and functioning of the system. In addition, ecosystem indices show that the system recovers rapidly during favourable conditions. The arti cial separation of the St Lucia and Mfolozi inlets underpins the most signi cant impacts on the water and salt budget of the lake and its reversal is key to the sustainability of the system.
Maximising the photobiological production of hydrogen using leachate, while monitoring algal photosynthesis using pam fluorometry.
(2014) White, Sarah Anne.; Trois, Cristina.; Anandraj, Akash.
Hydrogen is universally known as the most efficient renewable energy source capable of meeting global energy demands. Chlamydomonas reinhardtii has the ability to produce biohydrogen during the metabolic engineering of the photosynthetic pathways. The aim of this study was to 1) use leachate as a feedstock to enhance microalgal biomass and subsequent hydrogen production, 2) use Pulse Amplitude Modulated (PAM) Fluorometry to elucidate the role of photosystem one during hydrogen production, 3) use Nicotinamide Adenine Dinucleotide Phosphate (NADPH) fluorescence as an indicator of hydrogen production and 4) design a modular pilot scale biohydrogen bioprocessing system implementing experimental findings into a conceptual model. This resulted in a cost effective source of renewable hydrogen produced from waste. The use of 16% landfill leachate was found to increase biomass production by 26% as compared to using Tris- Acetate Phosphate (TAP) media alone. Hydrogen induction resulted in an increased gas synthesis of 37% as well as an increased production period of 8 days compared to the normal 5 days. Landfill leachate further reduced the costs as it acted as a free nutrient source with the added ecological advantage of leachate treatment. Hydrogen production was induced by sulphur depletion and physiological parameters were measured using PAM Fluorometry. Photosystem I was found to be dominant during hydrogen production while photosystem II was down-regulated due to the sulphur depletion and damaged D1 proteins. NADPH fluorescence was significantly correlated to hydrogen yields allowing for NADPH to be utilised as a molecular indicator for hydrogen synthesis. The overall functionality of this bioprocessing system relies on the optimum physiological functioning of cells. The above findings were implemented into a pilot scale design, maximising the physiological performance during hydrogen production. This study has contributed knowledge regarding the production of hydrogen gas from leachate, the physiological changes of photosystem I during hydrogen production and the use of NADPH fluorescence as an indicator. The fundamental theories of bioprocessing incorporate a firm understanding of cellular and biochemical processes. The use of molecular indicators determined from physiological studies can be used at pilot scale to improve overall efficiency of hydrogen production.
The use of commercial garden refuse at different degrees of maturity as an organic carbon source to bio-denitrify treated MSW landfill leachate.
(2014) Plüg, Björn.; Trois, Cristina.
Abstract available in PDF file.

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