Investigating pavement response to a moving vehicle: Characterisation of structural properties and direct measurement of structural rolling resistance

Research output: Book/ReportPh.D. thesis

Abstract

In this thesis, we use measurements of the pavement deflection slope, obtained with the Traffic speed deflectometer (TSD) technology, to analyze two road sections. We show, that the structural rolling resistance (SRR) is given by the deflection slope directly under the moving load. Furthermore, a simple pavement response model is developed and fitted to data. Based on the model fitting results, structural characteristics about the pavement are obtained. Overall, the thesis is split into four main parts:

1) The aim was to develop a new method for measuring rolling resistance. The idea is that the longitudinal deformation of the non-driven, rear-end tire axle is directly related to the rolling resistance. This deformation can in principle be measured using strain gauges. In practice, due to temperature effects in the axle, these measurements were not producing consistent results and the method needs further development to be brought to a routinely functioning state.

2) SRR for two road sections is found by estimating the deflection slope directly under the load through a linear interpolation between the two closest data points.
The method gives highly reproducible results (standard deviations from three repeated measurements between 4 and 10%) with a high spatial resolution. The influence of temperature is tested on a approximately10 km road segment, where the measured SRR coefficient values varies from 0.01%-0.03% of the load for 18 degrees and 0.01%-0.05% for 35 degrees. These values are small compared to typical tire rolling resistance values. The validity of the linear interpolation method was investigated by comparing to results from simulated curves using a continuum pavement model, and it was found to provide a valid estimate of SRR.

3) A simple one-dimensional pavement response model consisting of a viscoelastic Euler-Bernoulli beam resting on a Pasternak foundation is developed. A theoretical study of the model is performed, including a sensitivity analysis. It is found that only the behavior of the asphalt complex modulus within some range of wave numbers influence the modelled pavement response. Consequently, a simple viscoelastic model is used to describe top layer behavior and furthermore, the influence of velocity and temperature on the beam response is described.

4) The simple pavement response model is fitted to TSD data and is found to fit data very well. By analyzing the resulting best estimated parameter values, a connection between observed changes in the deflection slope data and changing structural characteristics of the pavement is derived. Surprisingly, the dominating source of damping is found to be the foundation damping. In fact, the top layer acts almost elastic in a majority of data. The ratio of maximum and minimum deflection slope amplitudes is shown to identify the dominating source of damping in a pavement within the model framework.
Lastly, a pilot study for determining asphalt complex modulus master curves based on TSD data at different temperatures and driving velocities is presented. The study illustrates that it is possible to create master curves describing the viscoelastic behaviour of the asphalt layer by applying the Time-Temperature Superposition principle to TSD data in conjunction with a sufficiently advanced road model. The presented method has the advantage that it uses a non-destructive measuring method and is easy to apply on large road sections. For future work, we recommend a study involving numerous different temperatures in order to cover a larger range of frequencies.
Original languageEnglish
Place of PublicationRoskilde
PublisherRoskilde Universitet
Number of pages302
Publication statusPublished - 2021

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