Permittivity Characterization of Unbound Granular Pavement Materials with a Modified Free-Space Approach

Muller, Wayne

doi:10.3141/2578-10

Cited by 3 publications

(11 citation statements)

References 29 publications

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“…Considering these issues and available techniques, a modified free‐space (MFS) approach was initially investigated as a potential method of measuring moist and compacted UBG samples for the purpose of calibrating GPR field measurements (Muller, Scheuermann, and Reeves ). Various aspects of the approach, including its accuracy compared to conventional apparatus and the influence of sample edges (Muller and Dérobert ), the influence of sample aspect ratio, antenna spacing, and beam pattern (Muller and Scheuermann ), previously have been investigated or discussed. While the approach has been used to measure the permittivity of moisture‐varying UBG samples from several quarry sources (Muller ), the influence of sample attributes such as density had not been investigated.…”

Section: Introductionmentioning

confidence: 99%

“…Various aspects of the approach, including its accuracy compared to conventional apparatus and the influence of sample edges (Muller and Dérobert ), the influence of sample aspect ratio, antenna spacing, and beam pattern (Muller and Scheuermann ), previously have been investigated or discussed. While the approach has been used to measure the permittivity of moisture‐varying UBG samples from several quarry sources (Muller ), the influence of sample attributes such as density had not been investigated. As the approach is intended as a means of calibrating GPR measurements, it is important to understand how these variations affect MFS and GPR measurements.…”

Section: Introductionmentioning

confidence: 99%

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A comparison of modified free‐space (MFS), GPR, and TDR techniques for permittivity characterisation of unbound granular pavement materials

Muller

Bhuyan

Scheuermann

2016

Near Surface Geophysics

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This paper reports on a laboratory experiment comparing permittivity measurements using a modified free-space approach to results using common-offset ground-penetrating radar and time-domain reflectometry on moist and compacted samples of unbound granular road pavement materials. In the first part of the experiment, unbound granular samples from the same source were prepared to varying moisture contents and a fixed target density. Separate samples were prepared for modified free-space and time-domain reflectometry testing, all of which were also measured using ground-penetrating radar. In the second part of the experiment, samples were mixed to a consistent gravimetric moisture content and varying densities before undertaking the modified free-space, time-domain reflectometry, and ground-penetrating radar measurements. Reasonably good agreement was found between modified free-space and ground-penetrating radar measurements, which also compared well with literature relations for crushed rock pavement materials. The time-domain reflectometry results were relatively consistent with those literature relations, although they appeared to deviate from the ground-penetrating radar and trend of modified free-space results for lower density and drier samples.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A comparison of modified free‐space (MFS), GPR, and TDR techniques for permittivity characterisation of unbound granular pavement materials

Muller

Bhuyan

Scheuermann

2016

Near Surface Geophysics

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“…These properties are determined by measuring scattering characteristics (Sparameters) using a Vector Network Analyser (VNA). Assuming the signal is a plane-wave travelling in low-loss conditions, the relative real ( r  ) and imaginary ( r    ) components of permittivity can be determined via [46]:…”

Section: Moisture-permittivity Relationsmentioning

confidence: 99%

“…The corresponding volumetric moisture content (θV) predictions presented in Figure 9 were calculated using the petro-physical relation developed previously [46]. The moisture content results determined via physical sampling are also shown for comparison in Figure 9 and are summarised in Table 2.…”

Section: Mullermentioning

confidence: 99%

“…Prior to equipment completion, semi-automated implementations of conventional [42] and two selfcorrecting geophysical methods [43] were investigated using numerical simulations. A modified free-space (MFS) permittivity characterisation approach was also developed to calibrate petro-physical relations for UBG pavement materials to enable field moisture predictions [42,[44][45][46]. In this paper an improved semi-automated analysis method is The second half was constructed in three layers -base, upper sub-base and lower sub-base.…”

Section: Introductionmentioning

confidence: 99%

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Characterising moisture within unbound granular pavements using multi-offset Ground Penetrating Radar

Muller¹

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Moisture has a significant influence on the performance and durability of unbound granular (UBG) pavements with thin bituminous surfacings, which form the vast majority of all-weather Australian roads. Techniques for measuring pavement moisture content are therefore important to quantify its influence on structural performance, enable early detection of problem areas, and to assess the condition of flood-affected pavements.Conventional techniques, however, require invasive probes or physical sampling which are impractical for large-scale investigations. Ground Penetrating Radar (GPR) techniques show promise, yet existing methods achieve only qualitative estimates, involve simplifications that limit accuracy or require complicated or laborious data analysis. The aim of this research was to develop a semi-automated approach using multi-offset GPR to quantitatively estimate the moisture content and depth of UBG pavement layers while maintaining data analysis simplicity.The research made use of a new type of 3-dimensional (3D) GPR technology able to continuously collect ground-coupled multi-offset gathers across the road while travelling at up to traffic speeds. To enable development of analysis methods prior to equipment completion, numerical simulations were used to model the expected response for typical pavement configurations. These data were used to test a semi-automated approach using interface tracking and conventional multi-offset geophysical analysis methods.They were also used to develop two novel self-correcting analysis techniques, Interface Matching (IM) and Ray-path Modelling (RM), which use migration and tomographic approaches, respectively.A permittivity characterisation approach, later called modified free-space (MFS), was also adapted for laboratory characterisation of UBG materials. It was used to calibrate petro-physical relations for these materials that enable pavement moisture estimates from the GPR measurements. As the MFS approach departs from conventional freespace methods, numerical modelling and a series of laboratory experiments were used to assess measurement accuracy and to determine the influence of sample edges, aspect ratio, and depth and antenna separation on the measurements. These investigations demonstrated that the MFS approach was suitable using the proposed equipment, sample sizes and for the range of relative permittivity values likely to be encountered. It also produced results that compared well with established apparatus over the frequency range relevant to pavement GPR.iii Measurements using this approach were also compared with conventional time-domain reflectometry (TDR) and common-offset GPR measurements of moisture-varying and density-varying UBG samples. The comparison showed similar results for most samples, although TDR reported lower relative permittivity values for drier and lowerdensity materials.Upon completion of the 3D GPR equipment, a revised analysis approach called Raypath Modelling-Semblance (RM-S) was developed. It was used to analyse multi-off...

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Semi-automatic determination of layer depth, permittivity and moisture content for unbound granular pavements using multi-offset 3-D GPR

Muller

2018

International Journal of Pavement Engineering

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Permittivity Characterization of Unbound Granular Pavement Materials with a Modified Free-Space Approach

Cited by 3 publications

References 29 publications

A comparison of modified free‐space (MFS), GPR, and TDR techniques for permittivity characterisation of unbound granular pavement materials

A comparison of modified free‐space (MFS), GPR, and TDR techniques for permittivity characterisation of unbound granular pavement materials

Characterising moisture within unbound granular pavements using multi-offset Ground Penetrating Radar

Semi-automatic determination of layer depth, permittivity and moisture content for unbound granular pavements using multi-offset 3-D GPR

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