In situ root identification through blade penetrometer testing – Part 2

field testing

Gerrit Meijer (Lead / Corresponding author), Anthony Bengough, Jonathan Knappett, Kenneth Loades, Bruce C. Nicoll

Research output: Contribution to journalArticle

4 Citations (Scopus)
9 Downloads (Pure)

Abstract

The spatial distribution, depths and diameters of roots in soil are difficult to quantify but important to know when reinforcement of a rooted slope or the stability of a plant is to be assessed. Previous work has shown that roots can be detected from the depth–resistance trace measured using a penetrometer with an adapted blade-shaped tip. Theoretical models exist to predict both forces and root displacements associated with root failure in either bending or tension. However, these studies were performed in dry sand under laboratory conditions, using acrylonitrile butadiene styrene root analogues rather than real roots. In this paper blade penetrometer field testing on two forested field sites, with Sitka spruce and pedunculate oak in sandy silt and clayey silt respectively, is used to evaluate models under field conditions. Root breakages could be detected from blade penetrometer depth–resistance traces and using complementary acoustic measurements. Predictions of additional penetrometer resistance at root failure were more accurate than the displacement predictions. An analytical cable model, assuming roots are flexible and fail in tension, provided the best predictions for Sitka roots, while thick oak roots were better predicted assuming bending failure. These matched the modes of failure observed in 3-point bending tests of the root material in each case. The presence of significant amounts of gravel made it sometimes difficult to distinguish between hitting a root or a stone. The root diameter could be predicted when root strength and stiffness, and soil penetrometer resistance were known and the right interpretative model selected. Estimates based on peak force were more accurate than those based on root displacement. This measurement procedure is therefore a potentially valuable tool to quantify the spatial distribution of roots and their reinforcement potential in the field.
Original languageEnglish
Pages (from-to)320-331
Number of pages12
JournalGéotechnique
Volume68
Issue number4
Early online date3 Aug 2017
DOIs
Publication statusPublished - Apr 2018

Fingerprint

penetrometer
Silt
Testing
Spatial distribution
Reinforcement
Bending tests
Gravel
Butadiene
Styrene
Cables
Sand
Acoustics
Stiffness
Soils
in situ
reinforcement
silt
prediction
spatial distribution
breakage

Cite this

@article{e996badf5cf248c8bf2b89982c17be84,
title = "In situ root identification through blade penetrometer testing – Part 2: field testing",
abstract = "The spatial distribution, depths and diameters of roots in soil are difficult to quantify but important to know when reinforcement of a rooted slope or the stability of a plant is to be assessed. Previous work has shown that roots can be detected from the depth–resistance trace measured using a penetrometer with an adapted blade-shaped tip. Theoretical models exist to predict both forces and root displacements associated with root failure in either bending or tension. However, these studies were performed in dry sand under laboratory conditions, using acrylonitrile butadiene styrene root analogues rather than real roots. In this paper blade penetrometer field testing on two forested field sites, with Sitka spruce and pedunculate oak in sandy silt and clayey silt respectively, is used to evaluate models under field conditions. Root breakages could be detected from blade penetrometer depth–resistance traces and using complementary acoustic measurements. Predictions of additional penetrometer resistance at root failure were more accurate than the displacement predictions. An analytical cable model, assuming roots are flexible and fail in tension, provided the best predictions for Sitka roots, while thick oak roots were better predicted assuming bending failure. These matched the modes of failure observed in 3-point bending tests of the root material in each case. The presence of significant amounts of gravel made it sometimes difficult to distinguish between hitting a root or a stone. The root diameter could be predicted when root strength and stiffness, and soil penetrometer resistance were known and the right interpretative model selected. Estimates based on peak force were more accurate than those based on root displacement. This measurement procedure is therefore a potentially valuable tool to quantify the spatial distribution of roots and their reinforcement potential in the field.",
author = "Gerrit Meijer and Anthony Bengough and Jonathan Knappett and Kenneth Loades and Nicoll, {Bruce C.}",
note = "The authors thank David Boldrin (University of Dundee/James Hutton Institute) for his assistance during the field work. G. J. Meijer acknowledges a studentship provided by Forest Research, funded by ClimateXChange, the Scottish Government’s Centre for Expertise on Climate Change. The James Hutton Institute receives funding from the Scottish Government.",
year = "2018",
month = "4",
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language = "English",
volume = "68",
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}

In situ root identification through blade penetrometer testing – Part 2 : field testing. / Meijer, Gerrit (Lead / Corresponding author); Bengough, Anthony; Knappett, Jonathan; Loades, Kenneth; Nicoll, Bruce C. .

In: Géotechnique, Vol. 68, No. 4, 04.2018, p. 320-331.

Research output: Contribution to journalArticle

TY - JOUR

T1 - In situ root identification through blade penetrometer testing – Part 2

T2 - field testing

AU - Meijer, Gerrit

AU - Bengough, Anthony

AU - Knappett, Jonathan

AU - Loades, Kenneth

AU - Nicoll, Bruce C.

N1 - The authors thank David Boldrin (University of Dundee/James Hutton Institute) for his assistance during the field work. G. J. Meijer acknowledges a studentship provided by Forest Research, funded by ClimateXChange, the Scottish Government’s Centre for Expertise on Climate Change. The James Hutton Institute receives funding from the Scottish Government.

PY - 2018/4

Y1 - 2018/4

N2 - The spatial distribution, depths and diameters of roots in soil are difficult to quantify but important to know when reinforcement of a rooted slope or the stability of a plant is to be assessed. Previous work has shown that roots can be detected from the depth–resistance trace measured using a penetrometer with an adapted blade-shaped tip. Theoretical models exist to predict both forces and root displacements associated with root failure in either bending or tension. However, these studies were performed in dry sand under laboratory conditions, using acrylonitrile butadiene styrene root analogues rather than real roots. In this paper blade penetrometer field testing on two forested field sites, with Sitka spruce and pedunculate oak in sandy silt and clayey silt respectively, is used to evaluate models under field conditions. Root breakages could be detected from blade penetrometer depth–resistance traces and using complementary acoustic measurements. Predictions of additional penetrometer resistance at root failure were more accurate than the displacement predictions. An analytical cable model, assuming roots are flexible and fail in tension, provided the best predictions for Sitka roots, while thick oak roots were better predicted assuming bending failure. These matched the modes of failure observed in 3-point bending tests of the root material in each case. The presence of significant amounts of gravel made it sometimes difficult to distinguish between hitting a root or a stone. The root diameter could be predicted when root strength and stiffness, and soil penetrometer resistance were known and the right interpretative model selected. Estimates based on peak force were more accurate than those based on root displacement. This measurement procedure is therefore a potentially valuable tool to quantify the spatial distribution of roots and their reinforcement potential in the field.

AB - The spatial distribution, depths and diameters of roots in soil are difficult to quantify but important to know when reinforcement of a rooted slope or the stability of a plant is to be assessed. Previous work has shown that roots can be detected from the depth–resistance trace measured using a penetrometer with an adapted blade-shaped tip. Theoretical models exist to predict both forces and root displacements associated with root failure in either bending or tension. However, these studies were performed in dry sand under laboratory conditions, using acrylonitrile butadiene styrene root analogues rather than real roots. In this paper blade penetrometer field testing on two forested field sites, with Sitka spruce and pedunculate oak in sandy silt and clayey silt respectively, is used to evaluate models under field conditions. Root breakages could be detected from blade penetrometer depth–resistance traces and using complementary acoustic measurements. Predictions of additional penetrometer resistance at root failure were more accurate than the displacement predictions. An analytical cable model, assuming roots are flexible and fail in tension, provided the best predictions for Sitka roots, while thick oak roots were better predicted assuming bending failure. These matched the modes of failure observed in 3-point bending tests of the root material in each case. The presence of significant amounts of gravel made it sometimes difficult to distinguish between hitting a root or a stone. The root diameter could be predicted when root strength and stiffness, and soil penetrometer resistance were known and the right interpretative model selected. Estimates based on peak force were more accurate than those based on root displacement. This measurement procedure is therefore a potentially valuable tool to quantify the spatial distribution of roots and their reinforcement potential in the field.

U2 - 10.1680/jgeot.16.P.204

DO - 10.1680/jgeot.16.P.204

M3 - Article

VL - 68

SP - 320

EP - 331

JO - Geotechnique

JF - Geotechnique

SN - 0016-8505

IS - 4

ER -