DEVELOPMENT OF LAYERED ELASTIC ANALYSIS PROCEDURE FOR PREDICTION OF FATIGUE AND RUTTING STRAINS IN CEMENT -STABILIZED LATERITIC BASE OF LOW VOLUME ROADS

ABSTRACT

It is generally known that the major causes of failure in asphalt pavement is fatigue cracking and rutting deformation, caused by excessive horizontal tensile strain at the bottom of the asphalt layer and vertical compressive strain on top of the subgrade due to repeated traffic loading. In the design of asphalt pavement, it is necessary to investigate these critical strains and design against them. This study was conducted to develop a simplified layered elastic analysis and design procedure to predict fatigue and rutting strain in cement-stabilized base, low-volume asphalt pavement. The major focus of the study was to develop a design procedure which involves selection of pavement material properties and thickness such that strains developed due to traffic loading are within the allowable limit to prevent fatigue cracking and rutting deformation. Analysis were performed for hypothetical asphalt pavement using the layered elastic analysis program EVERSTRESS for four hundred and eighty pavement sections and three traffic categories. A total of Ninety predictive regression equations were developed with thirty equations for each traffic category for the prediction of pavement thickness, tensile (fatigue) strain below asphalt layer and compressive (rutting) strain on top the subgrade. The regression equations were used to develop a layered elastic analysis and design program, “LEADFlex”. LEADFlex procedure was validated by comparing its result with that of EVERSTRESS and measured field data. The LEADFlex-calculated and measured horizontal tensile strains at the bottom of the asphalt layer and vertical compressive strain at the top of the subgrade were calibrated and compared using linear regression analysis. The coefficients of determination R2 were found to be very good. The calibration of LEADFlex-calculated and measured tensile and compressive strains resulted in minimum R2 of 0.992 and 0.994 for tensile (fatigue) and compressive (rgutting) strain respectively indicating that LEADFlex is a good predictor of fatigue and rutting strains in cement-stabilized lateritic base for low-volume asphalt pavement. The result of this research will enable pavement engineers to predict critical fatigue and rutting strains in low-volume roads in order to prevent pavement failures.