An instrumented oedometer was designed and constructed for the purpose of investigating at-rest and compaction-induced earth pressures in moist soils. The device has a split oedometer ring, and horizontal stresses are measured using load cells which support one half of the ring. Rapid cyclic loading was applied to compacted soil specimens, using a digital pressure regulator and a computer-based data acquisition system. The performance of the device was validated by performing tests on silicon rubber and Monterey sand. / Ph. D.

Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Microorganisms play an important role in the stability and maintenance of the ecosystem and in the condition of the soil. However, in their natural environment, microorganisms often experience changing and hostile conditions. They therefore need to be able to adapt physiologically and modify their micro-environment. Biofilm formation is one mechanism to establish favorable micro-environments. The extracellular polymeric substances (EPS) that are typically associated with biofilm formation may also have an impact on soil structure. The aim of this project was to evaluate the potential of microbial manipulation on EPS production and the possible impact thereof on soil structure in order to improve water retention. Specific objectives of this study included the screening of natural environments for EPS-producers, developing techniques to observe EPS production and accumulation in the pores between soil particles, measuring the effect of EPS production on soil water hydraulic gradient, as well as determining the fate and impact of EPS-producers when introduced to naturally-occurring soil microbial communities. Several environmental samples have been screened for EPS-producing microorganisms. Soil columns were then inoculated with these EPS-producers and the passage of 20 mlaliquots water through the columns measured at 3 or 4-day intervals. Microbes isolated from soil, through their EPS production capability proved to retain water more effectively than was the case for water-borne EPS-forming microbes. This phenomenon was further studied using flow cells, filled with soil and inoculated with the EPS-producers isolated from either soil or water. Fluorescence microscopy showed that the soil microbes produced EPS that clogged pores between sand particles more effectively. This clogging resulted in lowering the soil water hydraulic gradient. To evaluate the effect of EPS-producers on existing soil microbial communities, cell counts, Biolog™whole-community carbon utilization studies and T-RFLP (terminal-restriction fragment length polymorphism) analyses were performed. Shifts in the soil microbial community could not be readily seen by observing microbial numbers and T-RFLP-analysis, but was noticeable in carbon utilization patterns. / AFRIKAANSE OPSOMMING: Mikroorganismes speel 'n belangrike rol in die stabiliteit en instandhouding van die ekosisteem en in die kondisie van die grond. In hul natuurlike omgewing ervaar mikroorganismes dikwels veranderlike en ongunstige toestande. Mikroorganismes het dus nodig om hulself fisiologies aan te pas en verander hul mikro-omgewing daarvolgens. Biofilm-vorming is een meganisme om gunstige mikro-omgewings te skep. Die ekstrasellulêre polimeriese produkte (EPP) wat tydens biofilm-vorming gevorm word, mag ook 'n impak hê op die grondstruktuur. Die doel van hierdie projek was om die potensiaal van mikrobiese manipulasie op EPP-vorming te evalueer asook die moontlike impak daarvan op grondstruktuur wat sodoende waterretensie kon bevorder. Die spesifieke doelwitte van hierdie studie het ingesluit die isolasie van EPPproduseerders vanuit natuurlike omgewings, die ontwikkeling van verskeie tegnieke waarvolgens EPP-produksie en die akkumulasie daarvan in die porieë tussen gronddeeltjies bestudeer kon word, die effek van EPP-produksie op hidrouliese gradiënt van grondwater en om die lot en impak wat EPP-produseerders op natuurlike grondmikrobiese populasies te bepaal. Verskeie grond- en watermonsters was getoets vir die voorkoms van EPP-produserende mikroorganismes. Grondkolomme is geïnokuleer met EPP-produseerders en die vloei van 20 ml-volumes water deur die kolomme is gemeet met 3 of 4-dag intervalle. Grond-geïsoleerde mikrobes het beter waterretensie tot gevolg gehad as water- geïsoleerde mikrobes. Hierdie verskynsel was verder bestudeer deur die gebruik van vloeiselle, gevul met grond of sand en geïnokuleer met EPP-produseerders geïsoleer vanuit grond of water. Fluoressensie mikroskopie het aangetoon dat grondmikrobes EPP produseer wat die porieë tussen gronddeeltjies meer effektief verstop. Dié verstopping het gelei tot die verlaging van die grondwater se hidrouliese gradiënt wat bepaal is deur die gebruik van die konstante-vlak bepalingsmetode. Om die effek van EPP-produseerders op bestaande mikrobiese populasies te bepaal, is seltellings, Biolog™ heel-gemeenskap koolstofverbruik studies en T-RFLP (terminale-restriksie fragment-lengte polimorfisme) analises uitgevoer. Veranderinge in die mikrobiese populasie kon nie geredelik bloot deur die bepaling van mikrobiese getalle en T-RFLP-analise waargeneem word nie, maar wel met die koolstofverbruikspatrone.

published_or_final_version / abstract / Applied Geosciences / Master / Master of Science

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Applied Geosciences / Master / Master of Science

published_or_final_version / Applied Geosciences / Master / Master of Science

CSLIP2 (De Natale, 1987) is the only slope stability program that utilizes a "direction set" optimization routine in its search for the minimum safety factor. However, CSLIP2 which employs Powell's Conjugate Direction Method permits only the horizontal and vertical directions (x and y) to be used as the initial direction set. The efficiency of the existing search routine is improved by replacing the x-y coordinate directions with initial directions that are parallel to and perpendicular to the principal axis of the safety factor contours.

A project report submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in partial fulfillment of the requirements for the degree of Master of Science in Engineering. Johannesburg 1998. / Various studies have been done to show that labour-based construction can meet the high standards normally required in the construction of roads. The organisational requirements that were needed to ensure the efficient use of labour have also been dealt with in various studies. Tile need for alleviation of poverty, unemployment and the negative social impact thereof by increasing the labour input in construction is understood by all concerned. A further step is however necessary before the idea of increasing the . labour component in any kind of roadwork can be taken seriously. Engineers need to move forward from the policy and organisational issues associated with labour intensive construction and start to provide designers with sound and innovative engineering solutions to overcome the hurdles experienced on the ground. The study looks at the process of foam bitumen stabilisation of soils and gravels with a view of utilising this innovative method for labour intensive construction. The material after having been stabilised can be placed in a stockpile. Actual durations that the material can safely remain in stockpile have been determined in this study to be in excess of six months for recycled asphalt and in excess of four months for the foam stabilised sand. Foam stabilised gravel was also studied and showed that after a year in stockpile the material failed probably due to a weakening of the bitumen and aggregate bond. Covering the stockpiled material did not show any significant difference to that of a similar uncovered stockpile. The position within the stockpile also did not have much effect on the engineering properties of the stoc piled material. The fact that the foam stabilised material can be worked on when cold and that it can be stockpiled for several months implies that the material is labour friendly and can be used in labour intensive construction of road base course layers or wearing course layers. / AC2017

A project report submitted to the Faculty of Engineering, University of the Witwatersrand in partial fulfilment of the requirements for the degree of Master of Science in Engineering. / Until recently use of ionic chemical soil stabilisers seemed hit or miss. The paper by paige-Green and Bennett explains that the stabilisers work only on soils containing reactive clays. The author's findings confirm this conclusion. It was shown that a CBR test, which can be done in any road soils laboratory, can be used to measure the chanqe in strength caused by the treatment of the soil with a chosen ionic stabiliser. South Africa is faced with a serious unemployment problem. The World Bank and the International Labour Organisation have shown that employment in construction can be significantly increased by the use of labour instead of machinery. Field trials showed that ionic stabilisers can readily be applied labour intensively. These stabilisers could improve marginal materials to road-building standard and this could further reduce the dependence on machinery by reducing the need to transport quantities of high quality gravel. / Andrew Chakane 2019

Chiu, Ming Ho. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 139-155). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.v / Table of Contents --- p.vii / List of Tables --- p.xi / List of Figures --- p.xiii / List of Plates --- p.xiv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.1.1 --- Environment of Hong Kong --- p.1 / Chapter 1.1.1.1 --- Flat land area --- p.1 / Chapter 1.1.1.2 --- Population --- p.2 / Chapter 1.1.1.3 --- Climate --- p.2 / Chapter 1.1.2 --- Landslides in Hong Kong --- p.4 / Chapter 1.1.2.1 --- Landslide history --- p.4 / Chapter 1.1.2.2 --- Government actions on landslide prevention --- p.7 / Chapter 1.1.3 --- Slopes in Hong Kong --- p.8 / Chapter 1.1.4 --- Slope stabilization --- p.10 / Chapter 1.1.4.1 --- Conventional methods of slope stabilization --- p.10 / Chapter 1.1.4.2 --- Biotechnical stabilization --- p.13 / Chapter 1.2 --- Situation in Hong Kong --- p.16 / Chapter 1.2.1 --- Slope protection in the past --- p.16 / Chapter 1.2.2 --- Government action on improving slope appearance --- p.16 / Chapter 1.2.3 --- Proprietary slope greening techniques --- p.19 / Chapter 1.3 --- Vegetation growth on slopes --- p.22 / Chapter 1.3.1 --- Basic requirements of plants --- p.22 / Chapter 1.3.2 --- Potential problems of proprietary systems on shotcreted cut slopes --- p.24 / Chapter 1.3.2.1 --- Steep gradient --- p.24 / Chapter 1.3.2.2 --- Thin soil --- p.24 / Chapter 1.3.2.3 --- Rainfall seasonality --- p.25 / Chapter 1.4 --- Current study --- p.26 / Chapter 1.4.1 --- Objectives --- p.26 / Chapter 1.4.2 --- Significance --- p.26 / Chapter 1.4.3 --- Thesis layout --- p.27 / Chapter Chapter 2 --- Soil water status and vegetation of cut slopes --- p.30 / Chapter 2.1 --- Introduction --- p.30 / Chapter 2.2 --- Materials and methods --- p.36 / Chapter 2.2.1 --- Study site --- p.36 / Chapter 2.2.2 --- In situ measurements and substrate sampling --- p.43 / Chapter 2.2.3 --- Physical properties of substrates on slopes --- p.43 / Chapter 2.2.3.1 --- Slope angle --- p.43 / Chapter 2.2.3.2 --- Substrate thickness --- p.43 / Chapter 2.2.3.3 --- Soil moisture --- p.43 / Chapter 2.2.3.4 --- Soil texture --- p.43 / Chapter 2.2.3.5 --- Bulk density --- p.44 / Chapter 2.2.3.6 --- Water retention capacity --- p.44 / Chapter 2.2.4 --- Chemical properties of substrates on slopes --- p.44 / Chapter 2.2.4.1 --- pH --- p.44 / Chapter 2.2.4.2 --- Conductivity --- p.45 / Chapter 2.2.4.3 --- Organic matter --- p.45 / Chapter 2.2.4.4 --- Total Kjeldahl nitrogen --- p.45 / Chapter 2.2.4.5 --- Mineral nitrogen (ammonium and nitrate) --- p.45 / Chapter 2.2.4.6 --- Carbon:Nitrogen --- p.46 / Chapter 2.2.4.7 --- Total phosphorus --- p.46 / Chapter 2.2.4.8 --- Available phosphorus --- p.46 / Chapter 2.2.4.9 --- Major extractable cations --- p.46 / Chapter 2.2.5 --- Green coverage on slopes --- p.46 / Chapter 2.2.6 --- Statistical analysis --- p.47 / Chapter 2.3 --- Results --- p.47 / Chapter 2.3.1 --- Rainfall characteristics --- p.47 / Chapter 2.3.2 --- Soil moisture --- p.49 / Chapter 2.3.3 --- Green coverage --- p.52 / Chapter 2.3.4 --- Physical properties of substrate on slopes --- p.55 / Chapter 2.3.5 --- Chemical properties of substrate on slopes --- p.57 / Chapter 2.4 --- Discussion --- p.61 / Chapter 2.4.1 --- Soil moisture and vegetation growth --- p.61 / Chapter 2.4.2 --- Soil nutrients and vegetation growth --- p.66 / Chapter 2.4.3 --- Other substrate properties and vegetation growth --- p.69 / Chapter 2.5 --- Summary --- p.75 / Chapter Chapter 3 --- Surface runoff and soil erosion of cut slopes --- p.76 / Chapter 3.1 --- Introduction --- p.76 / Chapter 3.2 --- Materials and methods --- p.84 / Chapter 3.2.1 --- Study site --- p.84 / Chapter 3.2.2 --- Experimental setup --- p.84 / Chapter 3.2.3 --- Surface runoff and soil loss --- p.88 / Chapter 3.2.4 --- Nutrient loss in runoff --- p.89 / Chapter 3.2.4.1 --- Total Kjeldahl Nitrogen --- p.89 / Chapter 3.2.4.2 --- Mineral nitrogen (ammonium and nitrate) --- p.89 / Chapter 3.2.4.3 --- Total phosphorus --- p.89 / Chapter 3.2.4.4 --- Available phosphorus --- p.90 / Chapter 3.2.5 --- Other substrate properties --- p.90 / Chapter 3.2.5.1 --- Soil texture --- p.90 / Chapter 3.2.5.2 --- Bulk density --- p.90 / Chapter 3.2.5.3 --- Soil compaction --- p.90 / Chapter 3.2.5.4 --- Water retention capacity --- p.90 / Chapter 3.2.5.5 --- Organic matter --- p.90 / Chapter 3.2.6 --- Vegetation coverage and green coverage on slope --- p.91 / Chapter 3.2.7 --- Statistical analysis --- p.91 / Chapter 3.3 --- Results --- p.91 / Chapter 3.3.1 --- Meteorological characteristics --- p.91 / Chapter 3.3.2 --- Surface runoff and runoff coefficient --- p.92 / Chapter 3.3.2.1 --- Surface runoff and runoff coefficient between different treatments --- p.92 / Chapter 3.3.2.2 --- Surface runoff and runoff coefficient between different proprietary systems --- p.97 / Chapter 3.3.3 --- Soil loss --- p.98 / Chapter 3.3.3.1 --- Soil loss between different treatments --- p.98 / Chapter 3.3.3.2 --- Soil loss between different proprietary systems --- p.99 / Chapter 3.3.4 --- Nutrient loss --- p.99 / Chapter 3.3.4.1 --- Nutrient loss between different treatments --- p.99 / Chapter 3.3.4.2 --- Nutrient loss between different proprietary systems --- p.104 / Chapter 3.3.5 --- Substrate properties of proprietary systems --- p.104 / Chapter 3.3.6 --- Vegetation coverage and green coverage --- p.107 / Chapter 3.3.7 --- Relationship between rainfall and erosional parameters --- p.110 / Chapter 3.4 --- Discussion --- p.117 / Chapter 3.4.1 --- Surface runoff and runoff coefficient between different treatments --- p.117 / Chapter 3.4.2 --- Relationship between rainfall characteristics and surface runoff --- p.122 / Chapter 3.4.3 --- Soil loss between different treatments --- p.125 / Chapter 3.4.4 --- "Relationship between rainfall characteristics, surface runoff and soil loss" --- p.126 / Chapter 3.4.5 --- Nutrient loss between different treatments --- p.128 / Chapter 3.4.6 --- Surface runoff and erosional losses between different proprietary systems --- p.129 / Chapter 3.5 --- Summary --- p.132 / Chapter Chapter 4 --- Conclusions --- p.134 / Chapter 4.1 --- Summary of major findings --- p.134 / Chapter 4.2 --- Implications of the study --- p.136 / Chapter 4.3 --- Limitations of the study --- p.137 / Chapter 4.4 --- Suggestions for further investigation --- p.138 / References --- p.139 / Appendices --- p.156