Use of Falling Weight Deflectometer Multi-Load Data for Pavement Strength Estimation

摘要

The objective of this study is to develop a mechanistic-empirical method for assessing pavement layer conditions and estimating the remaining life of flexible pavements using multi-load level Falling Weight Deflectometer (FWD) deflections. A dynamic finite element program, incorporating a stress-dependent soil model, was developed to generate the synthetic deflection database. Based on this synthetic database, the relationships between surface deflections and critical pavement responses, such as stresses and strains in each individual layer, have been established. A condition assessment procedure for asphalt pavements that uses multi-load level FWD deflections has been developed using these relationships. The verification study was conducted using field data. The results indicate that the proposed procedure can estimate the base and subgrade layer conditions. It was found from the study for the nonlinear behavior of a pavement structure that an FWD test with a load of 12 kip or less does not result in any apparent nonlinear behavior of the subgrade in aggregate base pavements. The study also indicated that the deflection ratio obtained from multi-load level deflections may predict the type and quality of the base/subgrade materials. With regard to the condition assessment of the asphalt concrete (AC) layer, the AC layer modulus and the tensile strain at the bottom of the AC layer were found to be better indicators than deflection basin parameters. The procedures for performance prediction of fatigue cracking and rutting were developed for flexible pavements. The drastically increasing trend in fatigue cracking with time may not be predicted accurately using the proposed procedure. Such trends may be due to the environmental effects and the inconsistent distress measurements. Predicted rut depths using multi-load level deflections show good agreement with measured rut depths over a wide range of rutting. However, the procedure using single load level deflections consistently underpredicts the rut depths. It was concluded that the rutting prediction procedure using multi-load level deflections can estimate an excessive level of rutting quite well and, thus, improve the quality of prediction for rutting potential in flexible pavements. The layer condition assessment procedure and the remaining life prediction algorithms developed in this project were incorporated into APLCAP (Asphalt Pavement Layer Condition Assessment Program) version 2.0, the VisualBasic program developed under the NCHRP 10-48 project.