Mechanistic-Empirical Flexible Pavement Thickness Design: The Minnesota Method

This report documents the development of a mechanistic-empirical (M-E) flexible pavement thickness design method for use in Minnesota. The report includes a comprehensive literature review of the state of the practice. The Minnesota Road Research Project (Mn/ROAD) served as the primary source of data, in addition to information from the literature, during the development of the method.

The mechanistic pavement model, WESLEA, provided reasonably accurate pavement response data and was chosen as the model for Minnesota. Pavement material properties and traffic loads were characterized using Mn/ROAD data. These characterizations were used both as input to WESLEA and to calibrate pavement performance equations to Minnesota conditions. The two modes of distress considered in this method are fatigue cracking and rutting. Fatigue performance is a function of tensile strain at the bottom of the asphalt concrete layer while the rutting is a function of compressive strain at the top of the sub grade. It was recommended that load spectra be used to characterize traffic.

The computer program, ROADENT, resulted from this research. An interactive design tool, the program runs in a Windows environment. The report includes a user's guide.