Abstract:
Road building in Ethiopia is increasingly in demand to meet medium and long terms development programs. Roads
are constructed radiating from the capital city of the country in all direction. The objective of this research study is to evaluate the
flexible pavement deflections with respect to pavement depth using Software along Jimma to Seka road segment and compare
the laboratory results with the Ethiopian Road Authority (ERA) standards. Ever Stress Software (ESS) is a numerical analysis
technique to obtain the deflection of pavement layers. The methodology of this research was finding the sensitivity of the road
parameters (dimension, layers thickness, elastic modulus, Poisson’s ratio, loads and pressures) in reducing the major causes of
failure in asphalt pavement fatigue cracking and rutting due to vertical surface deflections, the critical tensile strains at the bottom
of the asphalt layer and the critical compressive strains on the top of subgrade. The analytical method used was the elastic
modulus and Poisson’s ratio of the pavement materials as design parameters after CBR results of each layers was obtained. The
expected outputs have shown that the displacement or deflection (uz) was as high as 0.38mm in the asphalt surface and gradually
decreased as the pavement thickness increased. Large values of deflections indicates an over stressed condition which results in
the pavement surface to crack and distortion as a results of fatigue or accumulated plastic deformation. Therefore, the relative
deflection of pavement layer decreases as the pavement depth increases.
