In situ measurements of near-surface hydraulic conductivity in engineered clay slopes
In situ measurements of near-surface hydraulic conductivity in engineered clay slopes
In situ measurements of near-saturated hydraulic conductivity in fine grained soils have been made at six exemplar UK transport earthwork sites: three embankment and three cutting slopes. This paper reports 143 individual measurements and considers the factors that influence the spatial and temporal variability obtained. The test methods employed produce near-saturated conditions and flow under constant head. Full saturation is probably not achieved due to preferential and by-pass flow occurring in these desiccated soils. For an embankment, hydraulic conductivity was found to vary by five orders of magnitude in the slope near-surface (0 to 0.3 metres depth), decreasing by four orders of magnitude between 0 and 1.2 metres depth. This extremely high variability is in part due to seasonal temporal changes controlled by soil moisture content (up to 1.5 orders of magnitude). Measurements of hydraulic conductivity at a cutting also indicated a four orders of magnitude range of hydraulic conductivity for the near-surface, with strong depth dependency of a two orders of magnitude decrease from 0.2 to 0.6 metres depth. The main factor controlling the large range is found to be spatial variability in the soil macro structure generated by wetting/drying cycle driven desiccation and roots. The measurements of hydraulic conductivity reported in this paper were undertaken to inform and provide a benchmark for the hydraulic parameters used in numerical models of groundwater flow. This is an influential parameter in simulations incorporating the combined weather/vegetation/infiltration/soil interaction mechanisms that are required to assess the performance and deterioration of earthwork slopes in a changing climate.
123-135
Dixon, N.
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Crosby, C.J.
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Stirling, R.
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Hughes, P.N.
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Smethurst, J.
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Briggs, K.
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Hughes, D.
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Gunn, D.
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Hobbs, P.
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Loveridge, F.
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Glendinning, S.
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Dijkstra, T.
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Hudson, A.
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5 February 2019
Dixon, N.
6272601b-f201-4828-898b-2b4b8d5e08c0
Crosby, C.J.
3860314d-1844-4c5f-b433-f032201a4c64
Stirling, R.
db08b140-8662-4c14-b889-0cf6a7d6c56d
Hughes, P.N.
6eb480ef-5702-4fbd-b022-7cd098c5c7be
Smethurst, J.
8f30880b-af07-4cc5-a0fe-a73f3dc30ab5
Briggs, K.
8974f7ce-2757-4481-9dbc-07510b416de4
Hughes, D.
d3b52ac5-5b40-4694-8350-927e4c292ecb
Gunn, D.
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Hobbs, P.
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Loveridge, F.
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Glendinning, S.
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Dijkstra, T.
32bcc951-6d68-4317-8c83-8335e45e67be
Hudson, A.
c834356f-d618-49d2-a8cc-cd338e1a87a4
Dixon, N., Crosby, C.J., Stirling, R., Hughes, P.N., Smethurst, J., Briggs, K., Hughes, D., Gunn, D., Hobbs, P., Loveridge, F., Glendinning, S., Dijkstra, T. and Hudson, A.
(2019)
In situ measurements of near-surface hydraulic conductivity in engineered clay slopes.
Quarterly Journal of Engineering Geology and Hydrogeology, 52 (1), .
(doi:10.1144/qjegh2017-059).
Abstract
In situ measurements of near-saturated hydraulic conductivity in fine grained soils have been made at six exemplar UK transport earthwork sites: three embankment and three cutting slopes. This paper reports 143 individual measurements and considers the factors that influence the spatial and temporal variability obtained. The test methods employed produce near-saturated conditions and flow under constant head. Full saturation is probably not achieved due to preferential and by-pass flow occurring in these desiccated soils. For an embankment, hydraulic conductivity was found to vary by five orders of magnitude in the slope near-surface (0 to 0.3 metres depth), decreasing by four orders of magnitude between 0 and 1.2 metres depth. This extremely high variability is in part due to seasonal temporal changes controlled by soil moisture content (up to 1.5 orders of magnitude). Measurements of hydraulic conductivity at a cutting also indicated a four orders of magnitude range of hydraulic conductivity for the near-surface, with strong depth dependency of a two orders of magnitude decrease from 0.2 to 0.6 metres depth. The main factor controlling the large range is found to be spatial variability in the soil macro structure generated by wetting/drying cycle driven desiccation and roots. The measurements of hydraulic conductivity reported in this paper were undertaken to inform and provide a benchmark for the hydraulic parameters used in numerical models of groundwater flow. This is an influential parameter in simulations incorporating the combined weather/vegetation/infiltration/soil interaction mechanisms that are required to assess the performance and deterioration of earthwork slopes in a changing climate.
Text
Dixon et al Hydraulic Conductivity paper QJEGH FINAL 01aug18
- Accepted Manuscript
More information
Accepted/In Press date: 1 August 2018
e-pub ahead of print date: 4 September 2018
Published date: 5 February 2019
Identifiers
Local EPrints ID: 422718
URI: http://eprints.soton.ac.uk/id/eprint/422718
ISSN: 1470-9236
PURE UUID: 2693d461-73ca-45ef-8a4c-dffa3ad62461
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Date deposited: 01 Aug 2018 16:30
Last modified: 12 Aug 2024 01:36
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Contributors
Author:
N. Dixon
Author:
C.J. Crosby
Author:
R. Stirling
Author:
P.N. Hughes
Author:
K. Briggs
Author:
D. Hughes
Author:
D. Gunn
Author:
P. Hobbs
Author:
S. Glendinning
Author:
T. Dijkstra
Author:
A. Hudson
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