Title: Air permeametry on outcrop analogues: a composite image of the Neogene aquifer, Belgium
Authors: Rogiers, Bart ×
Beerten, Koen
Smekens, Tuur
Huysmans, Marijke
Gedeon, Matej
Mallants, Dirk
Batelaan, Okke
Dassargues, Alain #
Issue Date: 24-Apr-2012
Host Document: Geophysical Research Abstracts vol:14
Conference: EGU General Assembly location:Vienna date:22-27 April 2012
Article number: EGU2012-1788-1
Abstract: Saturated hydraulic conductivity (Ks) is one of the most important parameters determining groundwater flow and
contaminant transport in both unsaturated and saturated porous media. While several well-established laboratory
methods exist for determining Ks, in-situ measurements of this parameter remain very complex. Since the 50’s,
and increasingly from the late 80’s, air permeameters are being used effectively as an indirect method to determine
Ks on outcrop sediments. In this paper, the heterogeneity within outcrop sediments that are analogues for the
Neogene aquifer hydrostratigraphic units in northern Belgium is studied with a hand-held air permeameter. This
aquifer, representing a major groundwater source, consists of several sandy geological units from Miocene to
Pleistocene age with a marine to continental origin. Moreover, it plays an important role in the Belgian deep
geological radwaste disposal studies, and is the subject of a safety assessment for a future low-level radwaste
surface repository. To characterise the variability between and within the different lithostratigraphical aquifer units,
804 air permeability measurements at cm-scale were performed on several outcrops that are analogues for the
sandy aquifer sediments and a highly heterogeneous aquitard. Equivalent meter-scale Ks tensors were calculated
numerically through the law of flow conservation to obtain the vertical anisotropy factor. The off-diagonal tensor
components were shown to be negligible.
To validate the air permeametry data, 18 additional constant head permeameter tests on 100 cm3 cores and 27 grain
size analyses based Ks assessments were performed on outcrop material. The comparison indicates that hand-held
air permeameters are very effective and useful tools to characterise the magnitude of hydraulic conductivity, as
well as it’s small-scale variability and anisotropy, on a broad range of sediment types.
However, a comparison with data from a previous borehole campaign on similar though not identical aquifer
sediments reveals that the Ks values predicted at the outcrops are systematically higher by at least a factor of 10
than the corresponding Ks distributions determined from the borehole cores. One explanation is the weathering
state of several-cm thick clay lenses, i.e. much less weathered in the aquitard than in the analogous outcrop with
correspondingly lower conductivities for the aquitard. This shows that transferring outcrop data to the subsurface
should be done with care because of different degrees of compaction, weathering states, etc.
Publication status: published
KU Leuven publication type: IMa
Appears in Collections:Division of Geology
× corresponding author
# (joint) last author

Files in This Item:

There are no files associated with this item.


All items in Lirias are protected by copyright, with all rights reserved.