Comparative Study of Flexible Pavement Design Methodologies

Abstract

Road deterioration, potholes, ruts, crack, and undulations, set evidence on the importance of investigating the causes of these defects and then offering a solution to eliminate them. Poor pavement thickness design is one of the most important reasons affecting road deterioration and distress. The overall objective of this study is to develop a good knowledge of flexible pavement design methodologies, their use, application, data required for design, advantages and disadvantages and compare among them. Also to develop a good knowledge of the new design technology of flexible pavement structures based on mechanistic analysis and the common empirical parameters used by AASHTO Guide for Design of Pavement. The use of empirical methods has been established and widely recognized approach to thickness design; however, their disadvantages are becoming more prevalent with the increase in understanding of mechanistic-empirical design. The new 2002 AASHTO 'Guide for Design of Pavement Structures' is based on mechanistic -empirical procedures. The research plan was to study and collect data for sample roads in Khartoum State (Alhuda Street) and national road (Atbara Heya Road) and in UAE (Al-ain Nahel Road) the data for design of these roads are subgrade strength (CBR and MR), traffic data, road location and climate conditions, The flexible pavement design methods applied were: TRL, AASHTO, AI, SPDM and Layers system. Comparison between results had been made in term of total thickness of pavement. It was found for case study1and 2 that AI method gave the smallest thickness, RN31 method gave the largest thickness, and SPDM and AASHTOO gave in between ,for case study3 the method that gave the smallest thickness was RN31, while the method that gave the largest thickness was AASHTO. Medium values were by SPDM and AI methods Method that gives results closer to the results of the program -AASHTO method was closer in result to SPDM in case study1 Alhuda Street while AI was the closer one in case study2 Atbara Heya and RN31 was the closer one in case study 3Alain Nahel road in term of total thickness. SPDM computer software program is effective and easy to be applied. Hence it is recommended to be used in pavement design.