Evaluation of the Traffic Speed Deflectometer data using simplified deflection model

Falling Weight Deflectometer (FWD) has been used by many road agencies worldwide for structural evaluation of both flexible and concrete pavements since the 1980s. With the development of Traffic Speed Deflectometer (TSD), the laser-based deflectograph is increasing used to perform continuous bearing capacity measurement at a range of driving speeds. The two main advantages of the TSD technology are; its ability to carry out continuous deflection measurements rather than at discrete points and the tests can be carried out at traffic speed without the need for lane closure in the case a stationary device such as the FWD. The objective of this paper is to study the deflection basins generated by TSD on flexible pavements using Simplified Deflection Model (SDM). The study shows that TSD data can be modelled accurately using SDM that can be represented in a mathematical form of Y = K-1 exp (-r/K-2). K-1 is equal to deflection at D-0 in micron and K-2 is the structural parameter at the respective sensor location r. It is observed that the majority of the pavement sections possess nonlinear subgrade behaviour in the TSD deflection data. The dynamic effects generated by the TSD axle load are likely to be the reason for the pavements to exhibit subgrade nonlinearity. A comparison between the FWD and TSD data shows a high level of correlation and a mathematical model has been established for estimation of FWD deflections using the TSD data. The study also shows that he theoretical deflections generated by the SDM are in good agreement with the actual deflection data obtained from FWD test. Statistical analysis confirms that the SDM generated D-0 deflections are not significantly different from the D-0 deflections recorded by FWD device. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.