Influence of temperature, vehicle overloading and tire pressure on flexible pavement performance
Nakazzi, Maria Theresa
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The purpose of this project was to investigate the influence of temperature, vehicle over loading and tire pressure on flexible pavement performance. Two case studies of Kawempe-Luwero road and Kampala Masaka road are used. The Kawempe – Luweero Road is one of the major roads in the country, passing through towns of Kawempe, Matugga, Kagoma, Wobulenzi, Luwero among others; linking the central region of Uganda to Northern Uganda and Southern Sudan. It covers a distance of approximately 32.3 kilometres. The Kampala – Masaka road passes through towns of Busega, Kyengera, Nsangi, Mpigi and Lukaya ending at Masaka; covering a distance of approximately 127 kilometres. The Ugandan Government’s recent focus on infrastructure development has greatly attracted new economic truck configurations with higher freight capacities which have resulted in accelerated pavement damage in form of load induced distress such as fatigue cracking and rutting. In light of this, this study presents a Mechanistic-Empirical approach using KENLAYER to estimate damage caused by vehicle characteristics like tire pressure and loading as well climatic conditions of temperature. In the present thesis, the two roads stated above are analysed by using a mechanistic computer program KENLAYER. The flexible pavements are analysed to evaluate their design life and the effect of factors like temperature, overloading (increasing axle load, load repetitions and VDF) and high tire pressure on pavement responses and pavement design life is studied. Using the results of analysis of these flexible pavements, a comparative assessment is carries out. Analysis results show that increasing temperature not only increases the stresses and strains in pavement structure but also leads to decrease in design life. Under overloading conditions (increase in GVW from 18T to 28T) design life decreased by more than 65% for Kawempe-Luweero road and by approximately 43% for Kampala-Masaka road. With the increase of tire pressure from 600 kPa to 1200 kPa, design life of Kawempe Luweero road decreased by more than 65% whereas that of Kampala-Masaka road decreased by more than 85%. From KENLAYER analysis results, it is concluded that flexible pavement compositions can be used to evaluate performance for higher load repetitions. Also mechanical characterisation of bituminous material is needed to be done for higher temperatures. Increasing GVW (Overloading) and tire pressure exceeding the permissible limits should be enforced strictly to stop the early deterioration of pavements.