Diagnosis of Pavement Structure Based on Spectxal Analysis of Surface Wave

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The purpose of this study is to develop a method to diagnose pavement structure using surface wave propagation. This is a method of nondestructive testing. The most commonly used nondestructive testing device for pavement is called FWD. According to the FWD, pavement layer moduli are estimated from measured surface deflections assuming layer thickness is known. Surface wave method is a method to diagnose pavement structure using the characteristics that a wave propagation speed in layered media depends on a frequency. It has been said that the method has a potential to estimate not only layer moduli but layer thickness. There are two approaches to estimate those, which are a simplified method and a theoretical inversion. Surface wave test has been aimed to find soil profiles and an applicability of the method to pavement has not been fully investigated. In this study, we examined whether the past findings can be applicable to pavement and we aim to develop a method suitable for pavement. The followings are found on the applicability of the past findings :1. It is impossible to estimate layer thickness using a simplified method.2. Theoretical dispersion curve is essential for inversion but found difficult to obtain in a se of pavement. New findings from this study are as follows :3. Rayleigh wave speed for a surface layer can be found from the test if a high frequency wave can be generated. When the thickness is 10cm, a frequency of 20kHz is required and 50kHz when it is 5cm.4. There is a strong correlation between thickness of surface layer and a slope of nearly straight line in a wave length-phase velocity diagram.