Rational approach to rutting rehabilitation decisions

In this thesis a study was conducted on the contributions of pavement structural layers to rutting of flexible pavements. Based on extensive literature review and analysis, computer simulations using the finite element method (FEM) were conducted to predict rutting failures. Rutting in hot mix asphalt (HMA) surface mixtures, base courses, and subgrades were simulated. Transverse surface profile characteristics indicative of failure within specific structural layers were determined in the form of simple distortion parameters. Specific criteria were developed for these distortion parameters and compared with full-scale accelerated pavement test (APT) data obtained from several sources. The findings of the initial study suggested that the relative contributions of the layers to rutting in a flexible pavement could be determined from an analysis of its transverse surface profile. A series of finite element analyses were conducted to refine the initial criteria. A matrix of typical pavement sections covering a wide range of structural sections was carefully selected so that the applicability of the refined criteria was maximized. Several issues concerning practical uses of the criteria, such as lateral support (shoulder width and type), wheel wander distribution, and heavy load/high tire pressure, were all investigated and resolved. A PC-based software called Profile Analysis Assistant Program (PAAP) was developed to facilitate FEM analyses and extracting distortion parameters from transverse surface profiles. To ease the use of the criteria an input table called Failure Identification Table (FIT) was developed using the Spreadsheet software. The appropriateness of the refined criteria was validated using trench data collected from various in-service pavements in different States. Good agreement was found between the predicted failure modes (location in the structural layer) and field-observed pavement failures. A method to estimate the contributions of individual pavement layer to total rutting was then developed in the form of a recommended draft AASHTO practice based on the study findings