Investigation and Development of a Contemporary Pavement Design Procedure for Rockhampton Regional Council

Abstract

This presentation will be a summary of the Industry Project I completed in 2022 and submitted as my final assessment in the Masters of Engineering Practice Course. The purpose of this project was to investigate and understand how road pavements perform in practice, and to use this understanding to develop a Pavement Design Procedure to be used by Rockhampton Regional Council in everyday practice. This project relates to common Council roads such as light to medium trafficked urban streets, and lower volume rural roads, constructed using traditional unbound granular pavements with bitumen surfacing or thin asphalt surfacing. I will start by discussing the outcomes of a literature review summarising the history of road pavements and road pavement design, the development of Road Pavement Design Manuals and Empirical Design Charts, the key points of traditional and current pavement design procedures, and the transition from Empirical to Mechanistic design methods . I will then discuss the outcomes of a visual assessment of pavement condition completed on 103 projects that had been constructed between 1993 and 2012, for the purpose of understanding how pavements were performing using existing pavement design methods. The observed defects were summarised to assist with understanding pavement deterioration mechanisms and guide procedural improvements. The outcomes of my investigation into the three main components of pavement design (i) Design Traffic Calculation, (ii) Determination of Subgrade CBR, and (iii) Pavement Thickness Design, will be discussed. For each pavement design component, a procedure has been recommended for implementation. The investigation into design traffic considered how accurately generic traffic load distribution (TLD) data and presumptive values represent heavy vehicle loading on typical Rockhampton streets and concluded that design methods using presumptive values applied to a percentage of the AADT were significantly over-estimating the total design traffic. The subgrade CBR investigation recommended accepting partially saturated subgrade conditions and outlined a testing regime to quantify the in situ subgrade strength and moisture conditions to be adopted for the site. This followed analysis of a case study that monitored subgrade moisture conditions every month for a period of 12 months, to better understand how partially saturated subgrades perform. Numerous pavement designs were completed comparing QTPDM Chart 1, Austroads Chart 8.4, and Austroads mechanistic-empirical design methods to determine the most appropriate method to calculate pavement thickness. An economic analysis was completed, concluding that the Austroads empirical design charts are the most suitable option for Rockhampton streets.