Simultaneous in-situ Stiffness and Anomalies Measurement on Pavement Subgrade Using Tomography Surface Waves Technique

Abstract

Non-destructive testing (NDT) has been developed as a effective tool in road evaluation system in order to in-situ assess the stiffness parameter of pavement layer, partcularly in conducting a quick assessment on soil subgrade layer. The NDT method based on the seismic surface wave measurement has been recently developed and applied for material evaluation of road-pavement, i.e. the shear wave velocity, Poisson's ratio and dynamic elastic modulus. In this paper, an improved technique of tomography surface waves measurement for simultaneously evaluation of stiffness and anomalies of pavement soil-subgrade is presented. The method performs the time-frequency spectrum analysis on recorded seismic wave data, which is non-destructively sampling the subgrade layers properties. An interactive wavelet analysis is used in the spectrum analysis to produce the real phase velocity and its corresponding shear wave velocity. Using principal of stress-strain material in elastic behavior, the elastic modulus parameter of soil-subgrade layers is then generated. This method is improved for producing the 2-D elastic modulus profile and at the same time, it shows the structure anomalies in the investigated subgrade layers. The higher elastic modulus values can be found in the subgrade layer with more homogeneous soil densities that may be produced from a good degree of compaction. While the lower elastic modulus can be identified in the subgrade layers which are having many structural anomalies. From this study, it can be shown that the tomography seismic surface wave technique is able to simultaneously determine the stiffness and structure anomalies within existing road pavement. Thus, this method can be potentially advanced and developed as an innovative material evaluation device for pavement structures.