A COMPARISON BETWEEN PAVEMENT RESPONSES FROM THE FALLING WEIGHT DEFLECTOMETER AND THOSE FROM TRUCK LOADING BASED ON THE LAYERED ELASTIC ANALYSIS

Abstract

Pavement responses e.g., surface deflections, tensile strains, and compressive strains etc. were determined from the multi-layered elastic analysis (LEA). The LEA has been widely accepted in most mechanistic design and performance analysis of the road pavements, where their structures were assumed to be homogenous, isotropic, linear-elastic, and finite thickness with modulus of elasticity and Poisson's ratio. The falling weight deflectometer (FWD) is a traditional tool for the structural condition evaluation of road pavements. In Thailand, a typical FWD loading stress of 700-800 kPa was practically adopted by the Department of Highways, while a tandem axle-dual wheel having a 690 kPa (100 psi) tire pressure and a 100 kN (10 metric tons) single axle load generated by the standard 10-wheel Thai truck (e.g., legal load permit of 25-ton gross weight) was considered in the pavement design and analysis. The objective of this paper is therefore to compare the pavement responses from the FWD and the standard Thai truck loads based on the LEA. Comparison results indicated that the average error was about 10% for 800-kPa FWD-standard Thai truck deflections, while 21% for 700-kPa FWD-standard Thai truck deflections. In case of tensile strain at the bottom of thin asphalt surface, the average error was respectively 2% and 14% for 800-kPa FWD-standard Thai truck and 700-kPa FWD-standard Thai truck. However, for thick asphalt surface, the average error was respectively 38% and 21% for 800-kPa FWD-standard Thai truck and 700-kPa FWD-standard Thai truck. In case of the compressive strain above the subgrade, the average error ranged from 7 to 11% for 800-kPa FWD-standard Thai truck and 8 to 12% for 700-kPa FWD-standard Thai truck.