Sustainability and Resilience of Transportation Infrastructure in African Countries

为了应对为非洲国家提供可持续和弹性基础设施的全球挑战，该提案汇集了来自杜伦大学、夸梅·恩克鲁玛科技大学（加纳）、比勒陀利亚大学（南非）和Nyaoro & Associates（坦桑尼亚）的主要研究人员。本提案中概述的研究将调查(i)在道路建设中使用可持续（当地发生的）建筑材料和（ii）气候变化对交通基础设施的影响。一个关键的共同要素将是在实验室和现场测试中测量吸力，使用杜伦大学开发的高吸力张力计。在设计和建造可持续的低流量道路（每天的交通量少于300辆车）时，将调查使用当地可获得的材料。对于小容量密封道路，道路环境（由气候、排水和施工细节控制）是影响道路性能的最重要因素，而不是交通荷载。该研究的新颖之处在于，通过非饱和土力学原理，获得了热带气候条件下道路施工材料基本行为的知识。目前，道路施工规范的要求与观察到的性能之间存在脱节。这可以解释为由于缺乏在这些环境中吸力的现场测量，对道路基础内的非饱和条件缺乏了解。基于在加纳和坦桑尼亚不同气候条件下的实地测量，在实验室保水测量的支持下，将有可能解决(i)调整规范和道路设计以适应当地材料；或（ii）调整或修改材料（通过稳定）以适应实际规格。非洲的气候变化表现为极端天气和降雨模式的变化。为了考虑气候变化的影响，将对南非的一条铁路线进行吸力和含水量测量。这些将用于识别由于湿/干循环而导致的交通基础设施的潜在恶化。这一恶化机制可能会因气候变化而加剧，因为由于旱季降水减少（甚至干旱）和雨季降雨更强，预计干湿循环的幅度会更大。与铁路基础设施应对气候和环境影响的弹性有关的另一个方面是铁路在重轴、循环载荷下的性能。人们认为地层的刚度与地层的不饱和行为有关，这种关系是理解地层长期性能的关键。这些测量结果将根据南非这一特定研究地点现有的12年历史数据进行解释。

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.