Research On The Structure Design Of Long Life Pavement In Sub Saharan Africa

Africa is one of the biggest continent in the world, hence it’s extended over an area of nearly 30 million km2 with a population of nearly 760 million people. In sub Saharan Africa, the roads and highways play an important role in the transportation system. Moreover when accounting all the transport modes in sub Saharan Africa the road transport occupies an important place and can be estimated to be 80%～90% of Africa’s urban and inter-countries transportation of goods. Sub Saharan Africa road network density is less than 4.2 km / sq km of which 16% of roads are paved. Currently the state of the road network can be summarized as: 44% of roads in a good condition of service; 22%and 34% respectively for the roads in a poor and medium condition of service.Overall it can be said that the sub Saharan Africa’s roads system is relatively at low level of service and this is due to different situations(pavement aging, rutted roads, serious damage) which actually become a shackle of our economy. Therefore, it is of great importance to address those problems for an economically stronger sub Saharan Africa.Based on the above Issues, this thesis titled “RESEARCH ON THE STRUCTURE DESIGN OF LONG LIFE PAVEMENT IN SUB SAHARAN AFRICA” was carried out and aims to:Firstly, present in details the current situation and main problems of the pavement structure in sub Saharan Africa, the environmental conditions, traffic conditions and common diseases types of the asphalt pavement analysis.Secondly, this thesis introduces the theory and method of the design of the most common asphalt pavement structure in sub Saharan Africa. Mainly based on the existing norms summarizes the sub-Sahara Africa highway asphalt pavement design in the process of heavy vehicle traffic, calculation of the risk, asphalt mixing material parameters, pavement cap level, allowable and actual bearing capacity, pavement structure…,and get to the determination of pavement structure.Then, based on the Sub-Sahara Africa asphalt pavement structure design theory and method; combined with Europe, America, China and other countries long-life pavement design concepts, design requirements, design criteria…; pre-designing three different structures of long life pavement such as full depth pavement, semi-rigid pavement and composite structures.Finally, according to the theory of elastic layered system, the mechanical properties of three typical long life pavement are analyzed by using the international large-scale general finite element software ABAQUS. And for each pavement structure two different types of three-dimensional finite element model(3D-FEM) were established. In the first case a Semi sinusoidal dynamic load was used in pavement structure without cracks in the pavement structure, in this case it’s question of analysis and comparison of structure mechanics response by the distribution of tensile strain at the bottom of the asphalt layer, tensile strain at the bottom of the base and Compressive strain on top of subgrade soil time history curves of the three kinds. The other is the fracture mechanics analysis of pavement structure under moving uniform load, in which the crack propagation law of different asphalt pavement structure is studied.