Electromagnetic properties of railway ballast

doi:10.1016/S0963-8695(00)00006-2

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Electromagnetic properties of railway ballast

Journal Article•DOI•

Electromagnetic properties of railway ballast

M. R. Clark¹, R. Gillespie¹, T. Kemp¹, D. M. McCann¹, Michael Forde¹ - Show less +1 more•Institutions (1)

University of Edinburgh¹

01 Jul 2001-Ndt & E International (Elsevier)-Vol. 34, Iss: 5, pp 305-311

TL;DR: In this article, the dielectric properties of railway track ballast using Ground Penetrating Radar (GPR) have been investigated for identifying defects in railway track bed and the implications of the findings for radar velocity are discussed.

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Abstract: Laboratory experiments were undertaken to identify and characterise the dielectric properties of railway track ballast using Ground Penetrating Radar (GPR). Better results were obtained with lower frequency antennas. Clear distinctions were obtained between wet and dry and clean and spent ballast. The laboratory experiment is described in detail and sample radar scan plots given — the final analysis of dielectric constants is also given. The implications of the findings for radar velocity are discussed. The application to identifying defects in railway track bed is discussed.

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Electrical properties of road materials and subgrade soils and the use of ground penetrating radar in traffic infrastructure surveys

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Timo Saarenketo

01 Nov 2006

TL;DR: In this paper, the authors focused on both the research results of studies on electrical properties of road materials and subgrade soils and their seasonal changes and the use of Ground Penetrating Radar technique in traffic infrastructure surveys.

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Abstract: This PhD thesis is composed of a synopsis and five published papers that are focused on both the research results of studies on electrical properties of road materials and subgrade soils and their seasonal changes and the use of Ground Penetrating Radar technique in traffic infrastructure surveys. The data for this survey was collected mainly in Finland, Texas, Scotland and Sweden and thus presents many kinds of road materials, subgrade soils and climate conditions. This research demonstrates that the GPR technique not only gives valuable structural information on the different types of structures and subgrade soils but it provides a wide range of information of the electrical properties of the materials under survey which can be further related to their mechanical performance. The best information will be gained if GPR data is analysed together with other non destructive testing data collected from the roads, railways and airports.

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162 citations

Cites background from "Electromagnetic properties of railw..."

...Fines are mainly formed through the mechanical wear, imposed by vibrations and loads from passing trains, and chemical wear caused by pollution and the effects of weather erosion on the larger particles (Clark et al. 2001)....
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...The ballast of a railway line must perform many different functions some of which are (Clark et al. 2001): reduce stresses applied to weaker interfaces, resist vertical, lateral and longitudinal forces applied to sleepers to maintain track position; and to provide drainage for water from the track structure. Ballast quality surveys focus on locating sections of clean and spent ballast. Spent ballast normally has a higher amount of fine particles than is allowed and can no longer fulfil the requirements for which it is being used (Clark et al. 2001). Fines are mainly formed through the mechanical wear, imposed by vibrations and loads from passing trains, and chemical wear caused by pollution and the effects of weather erosion on the larger particles (Clark et al. 2001). According to Nurmikolu (2005), mechanical wear is the most important factor increasing the fines content in ballast in Finland but organic material from external sources also has an important role in increasing water adsorption properties of ballast....
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...The ballast of a railway line must perform many different functions some of which are (Clark et al. 2001): reduce stresses applied to weaker interfaces, resist vertical, lateral and longitudinal forces applied to sleepers to maintain track position; and to provide drainage for water from the track structure. Ballast quality surveys focus on locating sections of clean and spent ballast. Spent ballast normally has a higher amount of fine particles than is allowed and can no longer fulfil the requirements for which it is being used (Clark et al. 2001). Fines are mainly formed through the mechanical wear, imposed by vibrations and loads from passing trains, and chemical wear caused by pollution and the effects of weather erosion on the larger particles (Clark et al. 2001). According to Nurmikolu (2005), mechanical wear is the most important factor increasing the fines content in ballast in Finland but organic material from external sources also has an important role in increasing water adsorption properties of ballast. However, in some countries coal dust from cargo trains has been the main source of fines in ballast. GPR can also detect, very reliably, if subgrade soil material has penetrated or mixed with the ballast (Hugenschmidt 2000, Brightwell & Thomas 2003). Dielectric value is a good indicator of ballast quality. The dielectric properties of ballast materials have been surveyed by Clark et al. (2001) and Sussman et al. (2002). The main parameters affecting the dielectric properties are moisture content and the level of fouling (Sussman et al. 2002). Clark et al. (2003a) have presented the dielectric values of good and poor quality ballast materials that have been compared in dry, moist and wet conditions (Table 6)....
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...The ballast of a railway line must perform many different functions some of which are (Clark et al. 2001): reduce stresses applied to weaker interfaces, resist vertical, lateral and longitudinal forces applied to sleepers to maintain track position; and to provide drainage for water from the track structure....
[...]
...The ballast of a railway line must perform many different functions some of which are (Clark et al. 2001): reduce stresses applied to weaker interfaces, resist vertical, lateral and longitudinal forces applied to sleepers to maintain track position; and to provide drainage for water from the track structure. Ballast quality surveys focus on locating sections of clean and spent ballast. Spent ballast normally has a higher amount of fine particles than is allowed and can no longer fulfil the requirements for which it is being used (Clark et al. 2001). Fines are mainly formed through the mechanical wear, imposed by vibrations and loads from passing trains, and chemical wear caused by pollution and the effects of weather erosion on the larger particles (Clark et al. 2001). According to Nurmikolu (2005), mechanical wear is the most important factor increasing the fines content in ballast in Finland but organic material from external sources also has an important role in increasing water adsorption properties of ballast. However, in some countries coal dust from cargo trains has been the main source of fines in ballast. GPR can also detect, very reliably, if subgrade soil material has penetrated or mixed with the ballast (Hugenschmidt 2000, Brightwell & Thomas 2003). Dielectric value is a good indicator of ballast quality. The dielectric properties of ballast materials have been surveyed by Clark et al. (2001) and Sussman et al....
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Journal Article•DOI•

Scattering analysis of ground-penetrating radar data to quantify railroad ballast contamination

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Imad L. Al-Qadi¹, Wei Xie¹, Roger Roberts²•Institutions (2)

University of Illinois at Urbana–Champaign¹, Geophysical Survey²

01 Sep 2008-Ndt & E International

TL;DR: In this article, a ground-penetrating radar (GPR) survey with multiple sets of 1 and 2 GHz air-horn antennae was conducted at the Transportation Technology Center, Inc. (TTCI) in Pueblo, Colorado.

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Abstract: This paper will evaluate ground-penetrating radar (GPR) as a non-destructive method to rapidly, effectively, and continually assess the conditions of railroad ballast. Compared to uniformly graded, clean ballast, fouled ballast has a finer, well-graded particle size with fewer air voids. Ballast under different conditions generates various GPR electromagnetic scattering patterns. A field GPR survey with multiple sets of 1 and 2 GHz air-horn antennae was conducted in summer 2005 at the Transportation Technology Center, Inc. (TTCI) in Pueblo, Colorado. The 2 GHz antenna was found to be more sensitive to the change in scattering pattern. Appropriate data processing was used to remove the effects of the rails to obtain clear GPR images of the subsurface layers. From the image analysis, ballast thickness, ballast fouling condition, and trapped water can be assessed.

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78 citations

Journal Article•DOI•

Signal processing of GPR data for road surveys

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Luca Bianchini Ciampoli, Fabio Tosti, Nikos Economou, Francesco Benedetto

19 Feb 2019

TL;DR: Results have proven the viability of the proposed signal processing method for data acquired on flexible pavements using GPR, provided recommendations on use of specific processing stages depending on survey requirements and quality of the raw dataset.

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Abstract: Effective quality assurance and quality control inspections of new roads as well as assessment of remaining service-life of existing assets is taking priority nowadays. Within this context, use of ground penetrating radar (GPR) is well-established in the field, although standards for a correct management of datasets collected on roads are still missing. This paper reports a signal processing method for data acquired on flexible pavements using GPR. To demonstrate the viability of the method, a dataset collected on a real-life flexible pavement was used for processing purposes. An overview of the use of non-destructive testing (NDT) methods in the field, including GPR, is first given. A multi-stage method is then presented including: (i) raw signal correction; (ii) removal of lower frequency harmonics; (iii) removal of antenna ringing; (iv) signal gain; and (v) band-pass filtering. Use of special processing steps such as vertical resolution enhancement, migration and time-to-depth conversion are finally discussed. Key considerations about the effects of each step are given by way of comparison between processed and unprocessed radargrams. Results have proven the viability of the proposed method and provided recommendations on use of specific processing stages depending on survey requirements and quality of the raw dataset.

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71 citations

Journal Article•DOI•

Railroad Ballast Evaluation Using Ground-Penetrating Radar: Laboratory Investigation and Field Validation

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Zhen Leng¹, Imad L. Al-Qadi¹•Institutions (1)

University of Illinois at Urbana–Champaign¹

06 Sep 2010-Transportation Research Record

TL;DR: In this article, controlled laboratory testing was conducted to measure accurately the dielectric constants of two common ballast types, granite and limestone, under various fouling and moisture conditions.

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Abstract: Ballast fouling in the railroad substructure is detrimental to the effectiveness of the railroad track and its structural capacity. The early detection of ballast fouling is of utmost importance to the safety of the rail system and its life-cycle cost-effectiveness. Ground-penetrating radar (GPR), a nondestructive evaluation tool, has shown its potential as a means of assessing the condition of the railroad substructure rapidly, effectively, and continuously. However, an unknown ballast dielectric constant and an unclear interface between clean and fouled ballast limit the accuracy of GPR assessment. In the present study, controlled laboratory testing was conducted to measure accurately the dielectric constants of two common ballast types, granite and limestone, under various fouling and moisture conditions. In addition, a time-frequency method, short-time Fourier transform (STFT), was used to demonstrate graphically the frequency energy variation with the depth of the ballast under various conditions. Th...

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55 citations

Journal Article•DOI•

Imaging attributes of railway track formation and ballast using ground probing radar

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R Jack¹, Peter Jackson¹•Institutions (1)

University of Nottingham¹

01 Dec 1999-Ndt & E International

TL;DR: In this article, the authors used Ground Probing Radar (GPR) technology to image attributes of the formation and ballast of railway track formations and found that changes in the quality of the image correlated well with marked changes observed in trial pits, and with significant changes in track geometry records.

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Abstract: Trial pitting and portable ballast samplers currently provide one means of assessing and monitoring the composition of railway track formations. A technique has been sought in which the lateral continuity of properties observed in these pits and cores can be assessed quickly with a view to characterising sections of the formation or ballast. The technique that is being developed by IMC Geophysics Ltd., in association with Scott Wilson Pavement Engineering, uses Ground Probing Radar (GPR) technology to image attributes of the formation and ballast. Trials have demonstrated that significant horizons can be imaged and that character changes along those horizons can be correlated with quality or structural variations. At sites where the ballast is relatively clean the interface between ballast and subgrade has been clearly imaged. In particular, changes in the quality of the image have correlated well with marked changes observed in trial pits, and with significant changes in track geometry records. From a combination of trial pits, cores, track geometry records and GPR it should be possible to improve the economics of track maintenance.

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49 citations

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Book•

Track Geotechnology and Substructure Management

[...]

Ernest T. Selig, John M. Waters

01 Jan 1995

TL;DR: In this article, the authors provide practical guidance for the design, construction, maintenance, and renewal of railway track as they relate to geotechnology, along with the properties of the ballast and subgrade materials.

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Abstract: This study provides practical guidance for the design, construction, maintenance, and renewal of railway track as they relate to geotechnology. Key functions of various track components are examined, along with the properties of the ballast and subgrade materials. In addition, the equipment and methods used for track installation, maintenance and renewal are explained in detail, as are the factors which determine the long-term geometric quality of the track.

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928 citations

Journal Article•DOI•

A Theoretical Evaluation of Impulse Radar Wave Propagation Through Concrete

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I. J. Padaratz¹, Michael Forde¹•Institutions (1)

University of Edinburgh¹

01 Jan 1995-Nondestructive Testing and Evaluation

TL;DR: In this article, a systematic parametric analysis was undertaken of electromagnetic wave propagation through concrete structures, and it was shown that the use of the simplified expression for wave velocity in relation to concrete structures is seen to be erroneous at lower frequencies - especially at higher conductivities.

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Abstract: It has been shown that one of the most important factors affecting a radar survey of a concrete structure is the operational frequency of the antenna. The operational choice of frequency is difficult as there is always a compromise between signal penetration and resolution. Whilst case histories have proved valuable sources of information, they have not yielded the systematic data needed by structural engineers specifying investigative studies. In the work reported herein, a systematic parametric analysis was undertaken of electromagnetic wave propagation through concrete structures. From this, the use of the simplified expression for wave velocity in relation to concrete structures is seen to be erroneous at lower frequencies - especially at higher conductivities. For a given frequency the skin depth )a measure of penetration( drops as conductivity increases. Also, the frequency of the electromagnetic pulse through concrete is shown to be the order of 75% of the centre frequency of the antenna a...

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23 citations

Journal Article•DOI•

Comparison of laboratory and simulated data for radar image interpretation

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C. Colla¹, C. D. Burnside¹, M. R. Clark¹, K. J. Broughton¹, Michael Forde¹ - Show less +1 more•Institutions (1)

University of Edinburgh¹

01 Dec 1998-Ndt & E International

TL;DR: In this paper, it has been shown that the output from in-house ray-tracing simulation software provides a means by which the impulse radar response of a structural system can readily be simulated.

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Abstract: It has been shown that the output from in-house ray-tracing simulation software provides a means by which the impulse radar response of a structural system can readily be simulated. Radar simulations were undertaken of re-bar targets in a tank. A 900 MHz commercial antenna was simulated. The simulations undertaken have shown the effects that target spacing and depth have on the radar signature shapes and the results compare well with real-case survey plots. Simulation data have been used to assess the output specification from a commercial antenna, with interesting findings. It is expected that simulation will allow the interpretation of actual surveys to be more readily understood, which will in turn allow a better engineering assessment to be made of a structure under investigation.

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12 citations