Abstract
In pavement management systems, deflection basin tests, such as the Falling Weight Deflectometer test, are common techniques that are widely used, while the surface wave test, i.e. the Spectral Analysis of Surface Wave test, is recently employed as an alternative technique in pavement evaluation and monitoring. In this paper, the performance of both dynamic non-destructive tests on pavement subgrade investigation is presented. Surface wave propagation between a set of receivers was transformed into the frequency domain using the Fast Fourier Transform technique and subsequently a phase spectrum was produced to measure the time lag between receivers. Using the phase difference method, an experimental dispersion curve was generated. Inversion analysis based on the 3-D stiffness matrix method was then performed to produce a shear wave velocity profile. The elastic modulus of pavement layers was calculated based on linear elastic theory. In the Falling Weight Deflectometer test, seven geophones were used to collect in situ deflection data. Based on a back-calculation procedure with the ELMOD software, the elastic modulus of each flexible pavement layer can be obtained. Both techniques are able to comprehensively investigate the elastic modulus of the subgrade layer in existing pavement non-destructively. The elastic modulus between the Spectral Analysis of Surface Wave method and the Falling Weight Deflectometer test on the subgrade layer is observed to be in a good agreement. A correlation of the elastic modulus of thesubgrade layer from both techniques is also presented.
Highlights
Experience has shown that predictions and diagnosis of pavement integrity are significant, especially since destruction will continuously occur once highway pavements are open for traffic
Compared to the profile obtained by core-drilling, the profile obtained by spectral analysis of surface wave (SASW) method which employs 3D inversion analysis indicates each pavement layer clearly
Compared to result obtained by falling weight deflectometer (FWD) test, the value of elastic modulus obtained by SASW method is higher
Summary
Experience has shown that predictions and diagnosis of pavement integrity are significant, especially since destruction will continuously occur once highway pavements are open for traffic. To ensure the highway pavements continue to serve the purpose, it is very important to periodically evaluate their conditions. The DT method (i.e. resilient modulus test, Marshall test) has the advantage of examining actual in-service material. This conventional method is more time consuming, destructive (coring is required) and costly if applied in routine monitoring of road works (AASHTO 1993; Asphalt Institute 1986). It provides only vertical information at certain points (Mulargia et al 2014)
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