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Rehabilitation of field tunnel erosion using techniques developed for construction with dispersive soils

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Hardie, MA and Cotching, WE and Zund, PR (2007) Rehabilitation of field tunnel erosion using techniques developed for construction with dispersive soils. Australian Journal of Soil Research, 45 (4). pp. 280-287. ISSN 0004-9573

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Abstract

Past repairs of field tunnel erosion using mechanical treatments (deep ripping, contour furrowing, contour
ripping, etc.) and reestablishment of perennial vegetation have often failed, resulting in further tunnelling. Techniques to
prevent ‘piping’ (tunnel erosion) in earth dams constructed using sodic clays have not been used in the repair of field tunnel
erosion; however, these techniques have the potential to reduce recurrent failure. Installation of an optical fibre cable in
a Grey Sodosol and Grey Dermosol at a site near Dunalley, Tasmania, in November 2001, resulted in the formation of a
380-m-long tunnel erosion system. Detailed site investigations and soil analysis in 2004 indicated that the tunnel erosion
resulted from the consequences of inadequate compaction during the installation of the optical fibre cable, and secondary
processes such as capture of surface and subsurface flow, dispersion of sodic clays, and translocation of dispersed clay
platelets through the poorly compacted fill. Repair works consisted of excavating the entire length of the tunnel system,
chemical amelioration with gypsum, compaction of repacked fill to reduce internal porosity, and installation of sand blocks
to capture and remove water moving along the reinstalled cable. Inspections conducted 2 years after completion of the
repair works indicated the site to be stable; however, it is acknowledged that this is too short an interval to adequately
assess the long-term stability of repair works and techniques employed at the site. Due to the costs associated with the
application of dam construction techniques, their use for the repair of field tunnel erosion is likely to only be justified
where continued erosion poses a risk of damage to high value infrastructure.

Item Type: Article
Keywords: sodicity, dispersion, piping, optic fibre cable, gypsum.
Journal or Publication Title: Australian Journal of Soil Research
Publisher: CSIRO Publishing
Page Range: pp. 280-287
ISSN: 0004-9573
Identification Number - DOI: 10.1071/SR06154
Date Deposited: 07 Apr 2008 14:39
Last Modified: 18 Nov 2014 03:35
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