Sustainability and Resilience of Transportation Infrastructure in African Countries

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To address the global challenge of providing sustainable and resilient infrastructure for African countries, this proposal brings together leading researchers from Durham University with Kwame Nkrumah University of Science & Technology (Ghana), University of Pretoria (South Africa) and Nyaoro & Associates (Tanzania). The research outlined in this proposal will investigate (i) the use of sustainable (locally occurring) construction materials in road construction and (ii) the impacts of climate change on transportation infrastructure. A key common element will be the measurement of suction in laboratory and field testing, using high suction tensiometers developed at Durham University. The use of locally available materials will be investigated for the design and construction of sustainable low volume roads (with traffic volumes of less than 300 vehicles per day). For low-volume sealed roads it is the road environment (controlled by climate, drainage and construction details) that is the most important factor influencing the road performance, rather than traffic loading. The novelty of the research proposed is to gain knowledge of the fundamental behaviour of road construction materials in tropical climate conditions through the principles of unsaturated soil mechanics. There is currently a disjoint between the requirements of specifications for road construction and observed performance. This can be explained by the lack of understanding of unsaturated conditions within the road base, due to a lack of field measurements of suction in these environments. Based on field measurements in different climatic conditions in Ghana and Tanzania, supported by water retention measurements in the laboratory, it will possible to address (i) adapting the specification and road design to suit local materials; or (ii) adapting or modifying the materials (by stabilisation) to suit a realistic specification.Climate change in Africa has been manifest by extreme weather and changing rainfall patterns. To consider the impacts of climate change, suction and water content measurements will be obtained for a railway line in South Africa. These will be used to identify potential deterioration of transportation infrastructure due to wetting/drying cycles. This deterioration mechanism is likely to be exacerbated by climate change, when dry/wet cycles are expected to have greater amplitude, due to a reduction in precipitation (even drought) in dry seasons and more intense rainfall in wetter seasons. Another aspect related to the resilience of railway infrastructure in response to climatic and environmental influences is the performance of railway formation under heavy axle, cyclic loading. It is thought that the stiffness of the formation is linked to the unsaturated behaviour of the layerworks and that this relationship is key to understanding the long-term performance of the formation. These measurements will be interpreted in the light of existing historical data at this specific research site in South Africa, that spans a period of 12 years.