EVALUATION OF ASPHALT PAVEMENT PERFORMANCE FROM PCI AND ITS DISTRESS DEPTH ANALYSIS USING EVERSTRESS SOFTWARE: A CASE STUDY ALONG BUTAJIRA – HOSSANA ROAD SEGMENT

Abstract

Research on road surface material performance is crucial for selecting alternative sub base materials to address costly maintenance issues and ensure longer-lasting roads in Ethiopia. The major objective of this research was to examine the existing pavement state and investigate fatigue cracking and rutting deformation failure, eventually intending to offer cost-effective maintenance and repair for the Butajira to Hossana road stretch in Ethiopia. In order to achieve the objective of this research, field visual inspection, field measurements, and laboratory tests on the most deteriorated section were conducted. The pavement condition index was used as part of the study approach to determine the degree and severity of pavement deterioration. Laboratory tests of CBR were conducted to obtain E from the corellation equation on the most deteriorated section to examine the sensitivity of road characteristics in analyzing fatigue cracking and rutting deformation within the asphalt pavement layers. This dual method allowed for a comprehensive evaluation of pavement conditions, combining field assessments with detailed laboratory analyses for a more nuanced understanding of distress mechanisms. The Everstress was employed to analyze stress-strain relationships and deformation characteristics of flexible pavements under diverse conditions. The road exhibits various defects, with a pavement condition index ranging from 34.16 to 70.3, indicating a condition ranging from 7.14% satisfactory to 11.43% very poor. The laboratory test results of subgrade soil reveal that in the subgrade soils have LL (46.14%) and PI (14.71%), maximum dry densities ranged from 1.37 g/cm³ to 1.84 g/m³, while the optimal moisture content was found to be between 12.9% and 25%. AASHTO and USCS classified the soils as A-7-6 and CL, suggesting that clayey component elements were the most common. The soil's overall assessment as a subgrade material is fair to bad. Among the pavement layers, asphalt layer demonstrated the highest horizontal strain (35.2 microstrains) and the lowest vertical strain (37.3 microstrains). Base course layer had an average vertical strain of -22 microstrain, while sub base layer showed an average vertical strain of -231.3 microstrain. In sub grade layer, the vertical strain was -425.1 microstrain at a depth of zero mm and -360.6 microstrain at a depth of 150mm. In conclusion, a substantial amount of the road is in fair, bad, and very poor condition and the early distress of the road identified due to the low quality of the sub grade material and the overloading of the traffic flow. It is recommended to conduct further comprehensive pavement structural testing and implement immediate repair measures to mitigate additional road damage