Due to urbanization, industrialization and population increase, a substantial increase occurred in the number of vehicles and hence large numbers of end-of-use tires are being disposed every year. The vast majority of these tires are stockpiled or used as a fuel for combustion which, in both cases, affects the environment detrimentally. The use of tire rubber in cement-stabilized aggregate mixtures (CSAMs) will ensure beneficial use of large quantities of these waste materials, saving natural resources and may enhance the properties of CSAMs especially these related to brittleness and sensitivity to fatigue failure. Research was undertaken to investigate, at macro and mesoscale levels, the effect of both rubber and degree of stabilization and their combination on the behaviour of CSAMs in terms of the most influential pavement design properties under different static and dynamic modes of loading. These properties are strength, stiffness and fatigue. A range of testing equipment, methodologies and tools was developed, suggested and implemented to perform this investigation. Further investigation was also conducted to provide better understanding of the damage and failure mechanism through quantitative studying of the fractured surface, internal structure and surface cracking patterns under different testing modes. The results of this study revealed that the addition of rubber has a negative effect on the compaction efficiency, compressive, flexural and tensile strengths while the stiffness, under different testing modes, was slightly reduced. In addition, a tougher mixture was produced after rubber-modification which means a change from a brittle to a more ductile behaviour. This behaviour was observed through different stiffness modulus evaluation methods. On the other hand, increase in cementation level has resulted in an increase in both strength and stiffness for both reference and rubberized mixtures. However, the decrease in the mixtures’ strength due to rubberization was more obvious in highly cemented mixtures than the lightly cemented ones. On the other hand, a greater decline in the mixtures’ stiffness, due to rubber incorporation, was observed at low cement contents. This behaviour is related to the void-like behaviour which depends, to large extent, on the relative stiffness between rubber and surrounding matrix. Quantification of the fractured surfaces and cracking pattern utilizing the photogrammatry and fractal dimension concepts, respectively, revealed that the addition of rubber resulted in rougher and more tortuous cracks and increases disperse-ability of these cracks. This means the rubber-modification changed the cracking pattern which implies better load transfer through the cracks and less risk of reflection cracking. The investigation of the internal structure, at mesoscale level, showed that the cracks were propagated through the rubber particles at all investigated cementation levels. This contributed to a lengthening of the crack path and to the delaying of crack propagation by absorbing and relieving the stresses at the crack tip, especially at the microcrack level. The latter mechanisms are behind toughness and fatigue improvement. Evaluation of rubber distribution revealed uniform distribution and this decrease as rubber content increases. The results also indicated an improvement in the fatigue life for all rubber replacement levels. This was valid at all cementation levels. In terms of modulus degradability, rubberization of the cemented mixture has only a slight effect on this property while larger permanent deformation was accumulated after rubber inclusion. It was observed that the poorly cemented mixtures showed greater stiffness modulus degradation. Pavement analysis and design study showed that the decrease in the mixtures’ strength overshadowed any improvement due to both mitigation of mixtures’ stiffnesses or fatigue life enhancement. However, this is not the case for poor rubber mixtures where this mixture showed better behaviour than the reference mixtures.

No description available.

This research has examined the application of machine learning and statistical methods for developing roadside particle (number/mass concentrations) prediction models that can be used for air quality management. Data collected from continuous monitoring stations including pollutants, traffic and meteorological variables were used for training the models. A hybrid feature selection method involving Genetic Algorithms and Random Forests was successfully used in selecting the most relevant predictor variables for the models from the variables selected based on their correlation with the PM\(_+\), PM\(_{2.5}\) and PNC concentrations. The study found that the hybrid feature selection can be used with both statistical and machine learning methods to produce less expensive and more efficient air quality prediction models. Among the machine learning models studied the Boosted Regression Trees (BRT), Random Forests (RF), Extreme Learning Machines (ELM) and Deep Learning Algorithms were found to be the most suitable for the predictions of roadside PM\(_+\), PM\(_{2.5}\), and PNC concentrations. The machine learning models performed better than the ADMS-road model in spatiotemporal predictions involving monitoring sites locations. Moreover, they performed much better in predicting the concentrations in street Canyons. The ANN and BRT were found to be suitable for air quality management applications involving traffic management scenarios.

A possible way to continuously monitor the whole water distribution system is to equip pipes with many microsensors. If these sensors are to be integrated within the pipe walls, it is important to assess their impact on the structural integrity of the pipes. In order to test a large number of samples, small polyethylene samples were produced using compression moulding and tested in different stress modes such as tension, bending, Charpy impact and flexural creep, with respect to different chip sizes (4 and 16mm\(^²\)), shapes (circle and square), numbers (one and two), orientations and position as well as sample dimensions and chip-polyethylene interface. It was discovered that the square chip contributes to the highest increase in the polymer stiffness, but significantly reduces its ductility. The 4mm\(^²\) circle causes the smallest disruption in the polymer integrity, especially when including multiple chips and when there is no adhesion. It significantly improves the impact resistance, while its effect in the short and long term bending stress modes is insignificant. The 16mm\(^²\) circle perpendicular to the load direction failed in bending at large strains. The optimal chip orientation for improving the impact strength and reducing the embrittlement effect in tension is parallel to the applied load.

The economy of Oman, was traditional in character before the development of the oil sector which set in motion the present structural transformation. Economic prosperity gave the opportunity to the public to possess their own private means of transport, thus resulting in a rapid increase in the number of vehicles in the country, particularly in the Muscat Area the capital city of the country. Free essential services such as health and education, and no taxes and duties have led to high disposable household income. Therefore, Muscat is witnessing rapid and successive land-use changes, expansion of the urban area and multi-car owning households. In the last two decades the population of Muscat increased considerably. This population growth was accompanied by a substantial expansion of Muscat's boundaries to provide homes, work places and other facilities. The topographical nature of the area limited the flat land available for housing, shops, schools, and other elements of the infrastructure. The resulting competition for space had as one of its consequences that insufficient land was allocated for car parking in the major activity centres, and the result was an acute shortage of parking spaces in these areas. The expansion of the Muscat Area was accompanied by changes in the employment and residential pattern. This resulted in a significant increase in number of vehicles, trips and commuting, and so the need for effective transport services and facilities became greater than ever before. The topographical features made it more difficult to provide sufficient transportation facilities. Development planning neglected the importance of arranging urban activities in such a way that the need for vehicle movements would be greatly reduced. It also resulted in low density population areas with street patterns mostly not designed for public transport services. This study sets out to discuss the problems of urban transportation in the Muscat Area and seeks to answer the following questions: What are the trip characteristics? How far do the natural topographical features inhibit the development of the Muscat road network? How does the existing network serve the needs of the area? How far can it cope with the traffic movement? Will the proposed major roads solve the present problems of traffic congestion and alleviate future ones? What are the main causes for traffic accidents? To what extent are car parking facilities adequate at the major activity centres? What is the role of Oman National Transport Company buses within the public transport system? The Muscat Area faces problems of traffic congestion and accidents, high demand on parking facilities and inadequate public transport. The situation is liable to deteriorate sharply in the next few years, unless effective action is taken. There is a need for a study that can provide immediate practical solutions and propose guidelines for future policy to ensure that the transport system is expanded and improved to cope with the needs arising from future growth. This study identifies factors contributing to the existing traffic problems with the intention of providing useful information which can help traffic planners and decision makers in understanding the nature of the problems, and finding solutions and guidelines for future policy. As far as methodology is concerned, a literature review is supported by fieldwork involving questionnaires and contacts with relevant authorities. Four types of surveys were conducted in order to collect information that can identify some of the factors that are contributory to the present problems. On the basis of the analysis of the data collected, urban transport problems are identified and discussed together with some possible solutions and recommendations.

Gravel filters are potentially a low cost, low maintenance water treatment solution. They require no mechanical or electrical parts and can operate without the addition of chemicals or the need for close supervision. As such, they are an appropriate technology for treating road runoff as a component of Sustainable urban Drainage Systems (SuDS) and as an initial stage of drinking water treatment in rural areas. However, the processes by which pollutant particles are removed in gravel filters are poorly understood and practical experience shows that many filters fail long before their expected design life is reached. For this reason gravel filters are little used for drinking water treatment and, when they are incorporated into SuDS, their removal efficiency and maintenance requirements are unpredictable. The aim of this thesis was to better understand particle removal processes and the implications for gravel filter design. This was achieved through a combination of lab-based experiments and numerical modelling. • The change in conservative tracer transport characteristics with pollutant particle accumulation was assessed through column experiments. • The spatial heterogeneity of particle accumulation was measured by collecting 3D data with magnetic resonance imaging (MRI). Multiple scans of filters allowed the temporal evolution of particle accumulation to be assessed. A method for processing the raw MRI data to yield the change in 3D pore geometry was developed, assessed and applied. • A simple method for extracting and comparing pore network characteristics at different stages of particle accumulation was applied to the MRI derived geometry. • Direct modelling of the 3D MRI pore geometry with the open source software OpenFOAM allowed correlation of flow velocities with particle accumulation at each point in the pore network. Lagrangian particle tracking was used to simulate the transport of a conservative tracer through the filter. Key findings were that spatial heterogeneity in particle accumulation was influenced by both initial pore geometry and the temporal evolution of the pore network with accumulation. This was attributed to the formation of high velocity preferential flow paths that were evident in both the 3D MRI data and the numerical model of that data. Pore networks exhibited a decrease in connectivity with accumulation and this was mirrored by a decrease in the volume of the filter that was accessible to a conservative tracer. Conclusions of this thesis are that MRI is a useful tool for non-invasively assessing the spatial variability of clogging in gravel filters and, when combined with numerical modelling of the pore geometry, for establishing the link between pore velocity and particle removal. The formation of preferential flow paths is detrimental to the pollutant removal efficiency of a filter and could explain why many filters fail to produce good quality effluent well before their physical pollutant storage capacity is reached.

Actualmente, el tramo de Av. Venezuela desde Próceres hasta España, presenta un suelo de baja capacidad de soporte, con un grado plástico entre medio a alto y con indicios de ser expansivo, siendo este el responsable de generar problemas de transitabilidad en épocas de lluvias, asentamientos a nivel de vereda y hundimientos en la vía con ausencia de pavimento. Debido a la problemática anterior, la presente tesis busca mejorar las propiedades físicomecánicas del suelo mediante la incorporación de agregados de carpetas asfálticas recicladas (CAR) más cenizas de aserrín (CDA), evaluándose las siguientes combinaciones: 50%CAR+4CDA+46%S, 50%CAR+8%CDA+42%S, 60%CAR+4%CDA+36%S, 60%CAR+8%CDA+32%S, 70%CAR+4%CDA+26%S y 70%CAR+8%CDA+22%S, estos porcentajes fueron ensayados en cada muestra de subrasante arcillosa: ML(C-01), CL(C-02) y CH(C-03). En base a los ensayos de laboratorio desarrollados, se obtuvo el 70%CAR+4%CDA como porcentajes óptimos de los estabilizantes, ocasionando en las tres subrasantes arcillosas los siguientes cambios: el IP, varió entre 0.55 a 1.00 veces su valor natural, determinándose 17.00%, 18.00% y 17.00% según sea la muestra, así mismo, la MDS, incrementó entre 2.23 a 3.24 veces su valor original, obteniéndose 1.907, 1.930 y 1.922 g/cm3 correspondientemente, en tanto, el CBR(95%), aumentó entre 2.23 a 3.24 veces su valor inicial, alcanzando 9.50%, 6.70% y 9.40% respectivamente, recalcándose que, las tres muestras pasaron de ser una subrasante inadecuada a una regular. Finalmente, para la ejecución de pavimento flexible cuya subrasante esté mejorada con 70%CAR+4%CDA se necesitará S/893,764.88 soles por cada 500m, no obstante, esta propuesta disminuye al 42.11% los impactos que tradicionalmente se generarán. / Due to the above problems, this thesis seeks to improve the physical-mechanical properties of the soil by incorporating aggregates of recycled asphalt pavement (RAP) plus sawdust ashes (SDA), evaluating the following combinations: 50%RAP+4%SDA+46%S, 50%RAP+8%SDA+42%S, 60%RAP+4%SDA+36%S, 60%RAP+8%SDA+32%S, 70%RAP+4%SDA+26%S y 70%RAP+8%SDA+22%S, these percentages were tested in each sample of clayey subgrade: ML(C-01), CL(C-02) and CH(C-03). Based on the developed laboratory tests, 70%RAP+4%SDA was obtained as optimal percentages of the stabilizers, causing the following changes in the three clayey subgrades: the IP varied between 0.55 to 1.00 times its natural value, determining 17.00%, 18.00% and 17.00% depending on the sample, likewise, the MDD increased between 2.23 to 3.24 times its original value, obtaining 1.907, 1.930 and 1.922 g/cm3 correspondingly, while the CBR(95%), increased between 2.23 to 3.24 times its initial value, reaching 9.50%, 6.70% and 9.40% respectively, emphasizing that the three samples went from being an inadequate subgrade to a regular one. Finally, for the execution of flexible pavement whose subgrade is improved with 70%RAP+4%SDA, it will cost a total of S/893,764.88 per 500m, however, this proposal reduces the impacts that will traditionally be generated to 42.11%.