Seasonal variations measured by TDR and GPR on an anthropogenic sandy soil and the implications for utility detection

Curioni, Giulio; Chapman, David; Metje, Nicole

doi:10.1016/j.jappgeo.2017.01.029

Cited by 22 publications

(13 citation statements)

References 38 publications

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“…Electromagnetic (EM) techniques have been widely used for measuring (Robinson et al 2008). Among these, time domain reflectometry (TDR) is a well-established method that has been used to measure and electrical parameters at point locations in the field based on the measurement of the apparent dielectric permittivity, K a (Herkelrath et al 1991;Robinson et al 2003a;Delin and Herkelrath 2005;Curioni et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Time domain reflectometry (TDR) potential for soil condition monitoring of geotechnical assets

et al. 2019

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The performance of geotechnical assets is influenced by various external factors including time and changing loading and environmental conditions. These changes could reduce the asset’s ability to maintain its function, potentially resulting in failure, which could be extremely disruptive and expensive to remediate; thus, the ability to monitor the long-term condition of the ground is clearly desirable as this could function as an early-warning system, permitting intervention prior to failure. This study demonstrates, for the first time, the potential of using time domain reflectometry (TDR) for long-term monitoring of the relative health of an asset (via water content and dry density) in a field trial where a clayey sandy silt was exposed to leaking water from a pipe. TDR sensors were able to provide detailed information on the variation in the soil conditions and detect abrupt changes that would relay a prompt for asset inspections or interventions. It is proposed that TDR could be used alone or together with other shallow geophysical techniques for long-term condition monitoring of critical geotechnical assets. Early-warning systems could be based on thresholds defined from the values or the relative change of the measured parameters.

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Section: Introductionmentioning

confidence: 99%

Time domain reflectometry (TDR) potential for soil condition monitoring of geotechnical assets

et al. 2019

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“…At 1 GHz, permittivity values range from just over 10.9–31.1. This interval is significant because the permittivity of the soil is likely to be within this range (Curioni, Chapman and Metje ). If the permittivity of the soil is similar to the permittivity of the root, it is unlikely that ground penetrating radar can detect it.…”

Section: Resultsmentioning

confidence: 99%

Direct measurements of tree root relative permittivity for the aid of GPR forward models and site surveys

Mihai

Gerea

Curioni

et al. 2019

Near Surface Geophysics

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Ground penetrating radar has been used extensively in near‐surface studies to detect underground objects and features typically located within a few metres beneath the surface. In urban areas, ground penetrating radar is widely used to study buried utilities such as pipes and cables. A more recent and unconventional application of ground penetrating radar is the detection of tree roots, which can interact negatively with the human infrastructure in a number of ways. However, the geophysical study of tree roots has proven quite challenging and site‐specific. Most tree roots (even coarse roots) have a small diameter and are hard to resolve through geophysical methods. In addition, the sheer amount of potential variability regarding the tree species, age, size, health and the subsurface environment (e.g., soil or a man‐made material such as concrete or asphalt) makes it very hard to implement a one‐size‐fits‐all approach. This is where robust, easily customizable forward models can be of assistance, indicating the range of detectable geophysical contrast and the limitations of the method, as well as the suitable antenna frequencies. Here, a vector network analyser with a commercial open‐ended coaxial probe was used to take direct measurements of the relative permittivity of freshly cut tree root segments at frequencies from 50 MHz to 3 GHz. The results were used as inputs to ground penetrating radar forward modelling using gprMax open source software, depicting various realistic scenarios which could be encountered in actual field surveys. The developed models help better understand the applicability, potential and limitations of ground penetrating radar surveys for detecting tree roots in different environments, aiding the development of future surveys. The notable variability in the tree roots is a significant consideration for surveys and forward models.

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“…Survey equipment is calibrated for average conditionsfor example, average velocity for groundpenetrating radar (GPR), and this is sometimes regarded as 'good enough'. This issue can be overcome by testing the ground conditions at the time of survey (Curioni et al, 2017) or by checking the detected depth against the measured depth at all inspection chambers and adjusting the detected depths accordingly. Nevertheless, the issue of increased confidence against increased accuracy, which is conflated in PAS128, remains.…”

Section: Discussionmentioning

confidence: 99%

Improved underground utilities asset management – assessing the impact of the UK utility survey standard (PAS128)

Metje

Hojjati

Beck³

et al. 2020

Proceedings of the Institution of Civil Engineers - Municipal E

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Buried utilities (e.g. gas, water, electricity, drainage), many installed decades ago, are vital urban support systems. Their locations are often not well documented, yet accurate location greatly helps replacement, rehabilitation and maintenance of existing services and is crucial for installation of new utilities: it minimises utility strikes / third party damage and the huge associated costs of delayed / additional streetworks. Several international standards and specifications aim to provide guidance on utility surveys to increase client confidence in their accuracy and repeatability. The most recent specification is PAS (Publicly Available Specification) 128 in the UK for underground utility detection, verification and location. This paper investigates the impact of PAS128 by comparing trial site survey results from different utility survey specialists with each other and with the vertical and horizontal accuracies at trial excavations. While the overall detection level was very good for all companies, the research revealed that the definition of quality level QLB1 needs to be reconsidered as it was not achieved in many places with respect to the vertical accuracy. It is recommended that future revisions of PAS128 differentiate between accuracy and confidence since detection by multiple sensing technologies increases the confidence, but not the accuracy as suggested by PAS128.

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Seasonal variations measured by TDR and GPR on an anthropogenic sandy soil and the implications for utility detection

Cited by 22 publications

References 38 publications

Time domain reflectometry (TDR) potential for soil condition monitoring of geotechnical assets

Time domain reflectometry (TDR) potential for soil condition monitoring of geotechnical assets

Direct measurements of tree root relative permittivity for the aid of GPR forward models and site surveys

Improved underground utilities asset management – assessing the impact of the UK utility survey standard (PAS128)

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