Unpaved roads comprise about 72 percent of the national and provincial road network in South Africa and substantially more of the total southern African road network. Significant costs are incurred annually by the authorities on the maintenance of these roads and enormous sums are associated with the cost of using these roads. Specifications for the use of materials for unpaved roads in southern Africa abound, the origin of most of these, however being rather obscure. It would appear that many of them have been transferred from other countries, mostly in the northern hemisphere. The geological materials used for construction in southern Africa, having been subjected to aeons of weathering and minimal major periods of recent glaciation, differ greatly from those in the northern hemisphere. One of the main objectives of this research was to investigate the performance of local geological materials used in wearing courses for unpaved roads and relate this to their geotechnical properties. This involved the sampling, testing and monitoring of 110 sections of unpaved road in the Transvaal and South West Africa over a period of more than three years. A large data base of gravel height, roughness, rut and corrugation measurements and the severity and extent of dustiness, stoniness, potholes, cracks, loose material, slipperiness and trafficability was compiled. The material and performance data were then used to develop performance related specifications and prediction models for roughness progression and gravel loss with the aim of providing improved unpaved roads and consequently reducing the road user and maintenance costs, in the national interest. Some of the savings will obviously be off-set to some extent by slightly increased materials location and construction costs. These costs are, however, shown to be minimal in comparison with the potential savings to the road user, the national economy and the generally improved quality of life of many road users in southern Africa. A good knowledge of the geotechnical properties of potential wearing course materials (which are significantly dependent on the geological origin) is necessary to differentiate good gravels from poor ones. / Ongeplaveide paaie maak ongeveer 72 persent uit van die nasionale en provinsiale padnetwerk in Suid Afrika en heelwat meer van die totale padnetwerk van suidelike Afrika. Groot kostes word jaarliks aangegaan deur die owerhede vir die instandhouding van hierdie paaie, asook enorme kosts wat in verband gebring kan word met die gebruik van hierdie paaie. Materiaalspesifikasies vir ongeplaveide paaie in suidelike Afrika is volop. Die oorsprong van die meeste hiervan is egter twyfelagtig en dit wil voorkom of dit uit ander lande, hoofsaaklik in die noordelike halfrond, afkomstig is. Die geologiese materiale gebruik vir padkonstruksie in suidelike Afrika verskil grootliks van die in die noordelike halfrond. Dit was onderwerp aan eeue se verwering en minimale groot-skaalse onlangse glasiale werking verskil grootliks van die. Een van die hoof doelwitte van hierdie navorsing was om ondersoek in te stel na die werkverrigting van plaaslike geologiese materiale wat gebruik word vir die slytlaag van ongeplaveide paaie en om dit in verband te bring met hul Geotegniese eienskappe. Dit het behels monsterneming en toets van materiale, asook monitering van 110 seksies ongeplaveide pad in Transvaal en Suid-Wes Afrika oor 'n tydperk van drie jaar. 'n Groot databasis bestaande uit inligting oor metings van gruishoogte, ongelykheid, spoor en sinkplaat asook inligting van graad en omvang van stof, klipperigheid, slaggate, krake, los materiaal, glibberigheid en rybaarheid is saamgestel. Die materiaal- en werkverrigtingsdata is toe gebruik om werkverrigtingsverwante spesifikasies op te stel, asook om modelle daar te stel om verswakking in gelykheid, en gruisverlies te voorspel. Die doel is om beter ongeplaveide paaie te voorsien en gevolglik die padverbruikers- en onderhoudskoste in nasionale belang te verminder. 'n Gedeelte van die besparing sal onvermydelik deur effens duurder konatruksiekoste en moontlike langer vervoerafstande van materiaal gekanselleer word. Hiedie koste is egter minimaal in verhouding tot die potensiele besparing vir die padgebruiker, die nasionale ekonomie en die algemene verbetering in lewenskwaliteit van baie padgebruikers in suidelike Afrika. 'n Goeie kennis van die geotegniese eienskappe van potensiele slytlaagmateriale (wat grootliks afhanklik is van geologiese oorsprong) is noodsaaklik om te differensieer tussen goeie an swak gruise. / Thesis (PhD)--University of Pretoria, 1989. / Civil Engineering / Thesis (PhD)--University of Pretoria, 1989. / Unrestricted

No description available.

Seabed surface sediments vary with active geomorphodynamics and sediment remobilization processes. Understanding relations between geotechnical sediment properties and sediment mobilization processes can potentially improve predictions of coastal erosion and hazard mitigation. Portable free fall penetrometers have emerged as an economic and useful tool for rapid geotechnical site characterization and uppermost sediment layer investigation. Acoustic methods have been used to assess seabed layering, scour evolution, and seabed morphology. However, there still exist major limitations in using these methods for classification and characterization of seabed sediment surface layers in the context of local sediment dynamics. Therefore, the goal of this research is to advance field data collection methods and field data availability towards advancing the current understanding and prediction of nearshore sediment dynamics. Geotechnical and geophysical measurements were conducted at different sites: Delaware Bay, Delaware; Pea Island, North Carolina; York River, Virginia; Potomac River, Maryland; Guadalupe River, Brazos River, Colorado River, Texas with different soil types and properties, hydrodynamic conditions, and morphological settings. The data collected was utilized to address the research goals through: (1) combining geotechnical and acoustic measurements to get better insight on sediment dynamics and erodibility, (2) proposing a framework that utilizes PFFP data to classify soil and estimate certain sediment properties (relative density and friction angle for sand and undrained shear strength for clays), relevant for local sediment dynamics, and (3) investigating how relevant geotechnical properties are reflected in acoustic, and specifically chirp sonar measurements. The findings of this research support the capability of portable free fall penetrometer to estimate sediment properties in topmost layers for different soil types such as friction angles, with an accuracy of ± 1° and undrained shear strength values, with <10% mismatches. Geoacoustic parameters such as acoustic impedance can also be calculated from acoustic measurements and correlated to certain sediment properties such as porosity and bulk density. Combining both measurements can yield better site characterization and accurate estimation of sediment properties for a better prediction of sediment dynamics. / Doctor of Philosophy / As the impacts of climate change seem to worsen, the likelihood of extreme events increases. This includes more frequent and severe events such as erosion, storm surges, melting glaciers, and sea level rise that impacts coastlines and coastal infrastructure. The increase in water levels increases the frequency of coastal hazards and flooding. These events result in devastating consequences, economically and environmentally, and disrupt people's lives all over the world. To adapt and reduce the severity of these consequences, there is a need to capture the changes in seabed, and a better understanding of seabed properties and their erodibility. This requires a reliable site characterization and an accurate estimate of seabed properties, which remain a challenge for different marine environments. There exist different site investigation methods to estimate seabed sediment properties that fall under geotechnical or geophysical types. One of the common geotechnical methods is a Portable free fall penetrometer (PFFPs), that presents a robust and economical tool for a rapid site assessment of topmost seabed layers. Geophysical tools, and mainly acoustic methods, are also often used to complement geotechnical methods due to their ability to cover vast areas in efficient time. However, both methods still face limitations in assessing seabed layers and properties. Therefore, the objective of this research is to develop a framework that paves the way for a reliable assessment of seabed properties using geotechnical and geophysical methods. Both methods were utilized for data collection in different locations across the US: Delaware Bay, Delaware; Pea Island, North Carolina; York River, Virginia; Potomac River, Maryland. Three additional sites Guadalupe, Brazos River, and Colorado Rivers, Texas were surveyed post hurricane Harvey that resulted in extreme flooding events. The measurements are collected from different coastal environments. This better account for the diversity in seabed to achieve a more generalized and well-integrated methodology to assess seabed layers under different conditions.

Geotechnical sediment properties such as moisture content, relative density, bearing capacity, and undrained shear strength have been discussed in the context of coastal sediment dynamics. However, these properties have rarely been assessed in their respective relevance or quantitatively related to sediment transport and erodibility. Also, to date there is no framework available for collecting direct measurements of these properties for estimating initiation of motion and erosion rates. Here, it is postulated that improving the ability to measure geotechnical sediment properties in energetic foreshore environments can improve our ability to predict coastal response to climate change. Through a series of field measurements, the research presented here (1) provides a framework for conducting geotechnical measurements of beaches, (2) advances portable free fall penetrometer (PFFP) data analysis in intertidal environments through the introduction of an impact velocity dependent strain-rate correction factor, (3) relates textural and sediment strength properties derived from PFFP measurements to an erosion rate parameter and hydrodynamically driven bed-level change, and (4) uses PFFP measurements to develop a sediment classification scheme in terms of soil behavior and erosion behavior for a mixed sediment type Arctic environment. Relationships between sediment properties other than grain size, most significantly void ratio, and erodibility parameters highlight the relevance of these measurements in geomorphodynamically active sandy beach environments. For the cohesive sediments in the Arctic, undrained shear strength was also related to an erosion rate parameter, allowing for a categorical framework for erodibility classification to be developed. The cohesive framework was combined with the relationships developed for sandy sediments and used to highlight areas of active sediment transport in the context of local morphodynamic and ice gouging processes. Finally, a simple case study showed how implementing in-situ erodibility parameters was important for long-term morphological modelling. The results represent a step forward in our ability to predict and mitigate climate change related issues from coastal erosion. / Doctor of Philosophy / Climate change driven impacts on coastal environments include increasing frequency and severity of storms, coastal erosion, and inundation of populated areas. Specifically for Arctic environments, warming has caused more sediment to be introduced into coastal waters as well as accelerated rates of permafrost melting and shoreline retreat and decreases in sea ice. One aspect of understanding how these changes will continue to affect coastal communities and our ability to predict climate change effects is understanding the role of sediment properties on sediment erosion and shoreline change. Physical and geomechanical (strength) properties of coastal sediments are important for a variety of coastal applications but have rarely been investigated in the context of quantifying, predicting, and assessing erosion, specifically in the context of field measurements. Towards this end, a series of field surveys were conducted along the coast of North Carolina at a sandy beach, and in Harrison Bay, Alaska, an Arctic coastal zone with both sandy and muddy sediments. Tools for taking physical samples of the beach and seabed, measuring the sediment strength, among other properties in place were used to characterize the local sediments. Once a framework was developed for characterizing the type of sediment, the measured properties were then related to measurements of erosion rate from a series of laboratory experiments performed on physical samples taken from the sites. Finally, one of the instruments for measuring sediment strength both on land and in the water was used to develop classification schemes for seabed sediments in terms of their erodibility. The results of this work highlight the importance of geotechnical properties for coastal sediment transport processes, reveal new relationships between sediment properties and properties quantifying erosion behavior, and offer a framework for future research to classify erodibility of coastal environments in the field with a single piece of equipment. Overall, the work presented here contributes to our ability to measure, quantify, and predict coastal response to climate change.

Crude oil is of economic importance to any nation. However its poor management and disposal method has resulted in oil spillage and ground contamination. Most emphasis on crude oil contamination on the environment has been on surface and ground water pollution, as well as plants and animals with little or no attention paid to the engineering properties of the contaminated soil. This research is thus aimed at investigating the effect of light crude oil contamination on the geotechnical properties of kaolinite clay soil. This research is a laboratory based experiment in which the contaminated soil was prepared by adding different percentages of light crude oil (2%, 5%, 8%, 10%, 15% and 20%) measured by weight of the dry soil sample and mixed until a uniform mixture was obtained. The British Standard Test Methods for Civil Engineering purposes BS 1377: 1990 (EUROCODE 7: EN 1997: 2-5) was adopted with few modifications. The calculations were based on the fact that the pore space in the contaminated soil is occupied by water and crude oil so water content was calculated from the fluid content and the rate of evaporation of crude oil during oven drying was also considered. The classification results showed that crude oil contamination caused an increase in linear shrinkage, liquid limit, plastic limit and plasticity index between 0% to 20% contaminations. The compaction result showed that there was an increase in maximum dry density while the optimum moisture content decreased between 0% and 15% of crude oil contamination. The result showed that the soil could not compact at 20% contamination and above. Also, the coefficient of permeability increased with increase in the percentage of crude oil contamination while the coefficient of consolidation value (Cv) increases with increase in the percentage of contamination. There was a decrease in the cohesion value and the frictional angle due to the introduction of the crude oil into the soil. Although crude oil altered the geotechnical properties of the kaolinite clay soil and reduced its strength, the soil can still be used for geotechnical purposed after remediation.

This thesis presents the results of an investigation of factors which influence the geotechnical properties of frozen mine backfill (FMB). FMB has extensive application potential for mining in permafrost areas. The uniaxial compressive strength (UCS) of hardened backfill is often used to evaluate mine backfill stability. However, the deformation behaviour and stiffness of the FMB are also key design properties of interest. In this thesis, uniaxial compressive tests were conducted on FTB and FCPB samples. Information about the geotechnical properties of FMB is obtained. The effects of FMB mix components and vertical compression pressure on the geotechnical properties of FMB are discussed and summarized. An optimum total water content of 25%-35% is found in which the strength and the modulus of elasticity of the FTB are 1.4-3.2 MPa and 35-58 MPa, respectively. It is observed that a small amount (3-6%) of cement can significantly change the geotechnical properties of FTB.

This thesis presents the results of an investigation of factors which influence the geotechnical properties of frozen mine backfill (FMB). FMB has extensive application potential for mining in permafrost areas. The uniaxial compressive strength (UCS) of hardened backfill is often used to evaluate mine backfill stability. However, the deformation behaviour and stiffness of the FMB are also key design properties of interest. In this thesis, uniaxial compressive tests were conducted on FTB and FCPB samples. Information about the geotechnical properties of FMB is obtained. The effects of FMB mix components and vertical compression pressure on the geotechnical properties of FMB are discussed and summarized. An optimum total water content of 25%-35% is found in which the strength and the modulus of elasticity of the FTB are 1.4-3.2 MPa and 35-58 MPa, respectively. It is observed that a small amount (3-6%) of cement can significantly change the geotechnical properties of FTB.

This thesis presents the results of an investigation of factors which influence the geotechnical properties of frozen mine backfill (FMB). FMB has extensive application potential for mining in permafrost areas. The uniaxial compressive strength (UCS) of hardened backfill is often used to evaluate mine backfill stability. However, the deformation behaviour and stiffness of the FMB are also key design properties of interest. In this thesis, uniaxial compressive tests were conducted on FTB and FCPB samples. Information about the geotechnical properties of FMB is obtained. The effects of FMB mix components and vertical compression pressure on the geotechnical properties of FMB are discussed and summarized. An optimum total water content of 25%-35% is found in which the strength and the modulus of elasticity of the FTB are 1.4-3.2 MPa and 35-58 MPa, respectively. It is observed that a small amount (3-6%) of cement can significantly change the geotechnical properties of FTB.

Le traitement des sols à la chaux est une technique ancienne et efficace dans les travaux de génie civil. Dans l'objectif du « zéro emprunt/zéro déchet » dans les travaux de terrassement routier, cette étude démontre que quelles que soient la plasticité et la médiocrité des propriétés hydromécaniques des sols argileux, le traitement à la chaux s'avère efficace. Les résultats expérimentaux concernant un sol argileux extrêmement plastique et gonflant montrent que les propriétés géotechniques s'améliorent avec le traitement à la chaux : le gonflement est éliminé, la plasticité réduite fortement et la résistance mécanique augmentée. Le suivi du processus physico-chimique de la réaction chaux–argile a permis de déterminer les quantités de chaux nécessaires aux changements instantanés ou/et durables du comportement hydromécanique des sols argileux traités. L'échange cationique poursuivi par la réaction pouzzolanique induisent dans les sols traités des modifications minéralogiques, texturales et structurales. Des hydrates calciques nouveaux sont formés grâce à la consommation de la chaux et des argiles. Ces hydrates tapissent les bords des particules argileuses et constituent une couche qui enrobent et assurent le lien entre les particules. Ces changements sont ainsi à l'origine des améliorations des propriétés géotechniques des sols traités. Les travaux de recherche réalisés démontrent que le processus et la cinétique des réactions chaux– argile dépendent du cation échangeable, de la quantité de chaux disponible, de la température de maturation et de la structure de l'argile : smectite, illite ou kaolinite. / Lime treatment techniques have largely been developed across the word mainly in civil engineering works. The context of sustainable development implies to improve the rate of reuse of clay soils in the earthworks. This study demonstrates that whatever the plasticity and poor hydromechanical properties of clay soils, the lime treatment is effective. Experimental results on highly plastic clay soil show that all geotechnical properties progress with the lime treatment: the swelling is eliminated, the plasticity is reduced greatly and the strength increases. Monitoring the physicochemical lime-clay reaction allowe to determine the quantities of lime required for short term and/or long term changes in the hydromechanical behaviour of treated clay soils. The cation exchange pursued by the pozzolanic reactions induced mineralogical, textural and structural changes in the treated soil. New hydrates are formed through the consumption of lime and clay. These hydrates contour the edges of clay particles and formed a layer which coat and provide the link between particles. These changes are well behind improvements in geotechnical properties of treated soil. The research conducted in this thesis shows that the process and the kinetics of lime-clay reactions depend on the exchangeable cation, the amount of lime available, to the curing temperature and the structure of the clay smectite, illite and kaolinite.

This thesis presents the results of an investigation of factors which influence the geotechnical properties of frozen mine backfill (FMB). FMB has extensive application potential for mining in permafrost areas. The uniaxial compressive strength (UCS) of hardened backfill is often used to evaluate mine backfill stability. However, the deformation behaviour and stiffness of the FMB are also key design properties of interest. In this thesis, uniaxial compressive tests were conducted on FTB and FCPB samples. Information about the geotechnical properties of FMB is obtained. The effects of FMB mix components and vertical compression pressure on the geotechnical properties of FMB are discussed and summarized. An optimum total water content of 25%-35% is found in which the strength and the modulus of elasticity of the FTB are 1.4-3.2 MPa and 35-58 MPa, respectively. It is observed that a small amount (3-6%) of cement can significantly change the geotechnical properties of FTB.