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Title: In situ measurements of near-surface hydraulic conductivity in engineered clay slopes
Authors: Dixon, Neil
Crosby, Chris
Stirling, Ross A.
Hughes, Paul N.
Smethurst, J.A.
Briggs, Kevin
Hughes, David
Gunn, David
Hobbs, P.
Loveridge, F.
Glendinning, Stephanie
Dijkstra, Tom
Hudson, A.
Keywords: Hydraulic conductivity
Engineered fill
Field measurement
Near-surface
Issue Date: 2018
Publisher: © The authors. Published by the Geological Society
Citation: DIXON, N. ... et al, 2018. In situ measurements of near-surface hydraulic conductivity in engineered clay slopes. Quarterly Journal of Engineering Geology and Hydrogeology, 52 (1), pp.123-135.
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 0.3 and 1.2 metres depth. This extremely high variability is in part due to seasonal temporal changes controlled by soil moisture content, which can account for up to 1.5 orders of magnitude of this variability. 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.
Description: This paper is closed access until 31 August 2019.
Sponsor: This paper is an output from iSMART, a collaborative research project funded by the UK Engineering and Physical Sciences Research Council (Grant number EP/K027050/1).
Version: Accepted for publication
DOI: 10.1144/qjegh2017-059
URI: https://dspace.lboro.ac.uk/2134/34253
Publisher Link: https://doi.org/10.1144/qjegh2017-059
ISSN: 1470-9236
Appears in Collections:Closed Access (Architecture, Building and Civil Engineering)

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