The University of Southampton
University of Southampton Institutional Repository

Groundwater flow into underground openings in fractured crystalline rocks: an interpretation based on long channels

Groundwater flow into underground openings in fractured crystalline rocks: an interpretation based on long channels
Groundwater flow into underground openings in fractured crystalline rocks: an interpretation based on long channels
Rethinking an old tracer experiment in fractured crystalline rock suggests a concept of groundwater flow in sparse networks of long channels that is supported by results from an innovative lattice network model. The model, HyperConv, can vary the mean length of ‘strings’ of connected bonds, and the gaps between them, using two independent probability functions. It is found that networks of long channels are able to percolate at lower values of (bond) density than networks of short channels. A general relationship between mean channel length, mean gap length and probability of percolation has been developed which incorporates the well established result for ‘classical’ lattice network models as a special case. Using parameters appropriate to a 4-m diameter drift located 360 m below surface at Stripa Mine Underground Research Laboratory in Sweden, HyperConv is able to reproduce values of apparent positive skin, as observed in the so-called Macropermeability Experiment, but only when mean channel length exceeds 10 m. This implies that such channel systems must cross many fracture intersections without bifurcating. A general relationship in terms of flow dimension is suggested. Some initial investigations using HyperConv show that the commonly observed feature, ‘compartmentalization’, only occurs when channel density is just above the percolation threshold. Such compartments have beeen observed at Kamaishi Experimental Mine (Japan) implying a sparse flow network. It is suggested that compartments and skin are observable in the field, indicate sparse channel systems, and could form part of site characterisation for deep nuclear waste repositories.
1431-2174
1-56
Black, John H.
96c3928f-2eb7-44e2-8176-0ec8fb723b34
Woodman, Nicholas
9870f75a-6d12-4815-84b8-6610e657a6ad
Barker, John
33bf9dec-cc9b-451c-8192-46099e316b6d
Black, John H.
96c3928f-2eb7-44e2-8176-0ec8fb723b34
Woodman, Nicholas
9870f75a-6d12-4815-84b8-6610e657a6ad
Barker, John
33bf9dec-cc9b-451c-8192-46099e316b6d

Black, John H., Woodman, Nicholas and Barker, John (2016) Groundwater flow into underground openings in fractured crystalline rocks: an interpretation based on long channels. Hydrogeology Journal, 1-56. (In Press)

Record type: Article

Abstract

Rethinking an old tracer experiment in fractured crystalline rock suggests a concept of groundwater flow in sparse networks of long channels that is supported by results from an innovative lattice network model. The model, HyperConv, can vary the mean length of ‘strings’ of connected bonds, and the gaps between them, using two independent probability functions. It is found that networks of long channels are able to percolate at lower values of (bond) density than networks of short channels. A general relationship between mean channel length, mean gap length and probability of percolation has been developed which incorporates the well established result for ‘classical’ lattice network models as a special case. Using parameters appropriate to a 4-m diameter drift located 360 m below surface at Stripa Mine Underground Research Laboratory in Sweden, HyperConv is able to reproduce values of apparent positive skin, as observed in the so-called Macropermeability Experiment, but only when mean channel length exceeds 10 m. This implies that such channel systems must cross many fracture intersections without bifurcating. A general relationship in terms of flow dimension is suggested. Some initial investigations using HyperConv show that the commonly observed feature, ‘compartmentalization’, only occurs when channel density is just above the percolation threshold. Such compartments have beeen observed at Kamaishi Experimental Mine (Japan) implying a sparse flow network. It is suggested that compartments and skin are observable in the field, indicate sparse channel systems, and could form part of site characterisation for deep nuclear waste repositories.

Text
Long channel concept Final inc figs.pdf - Accepted Manuscript
Download (3MB)

More information

Accepted/In Press date: 2 December 2016
Organisations: Infrastructure Group

Identifiers

Local EPrints ID: 403640
URI: https://eprints.soton.ac.uk/id/eprint/403640
ISSN: 1431-2174
PURE UUID: 4b719e81-3887-4ef8-9a6f-062a1a138333
ORCID for Nicholas Woodman: ORCID iD orcid.org/0000-0002-5571-0451

Catalogue record

Date deposited: 06 Dec 2016 16:43
Last modified: 06 Jun 2018 12:38

Export record

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×