3029
Hydraulic conductivity of compacted clay liners moisture-conditioned and permeated
with saline coal seam gas water
La conductivité hydraulique de l'humidité argile compactée doublures conditionné et imprégné avec
de l'eau salée gaz de houille couture
Indrawan I.G.B., Williams D.J., Scheuermann A.
The University of Queensland, Brisbane, Australia
ABSTRACT: The effects on the hydraulic conductivity of compacted clays, commonly used for lining coal seam gas (CSG) water
storage ponds, of moisture conditioning and permeating with CSG water are investigated. Four kaolinite-dominant clays were mixed
with CSG and deionised waters, compacted to varying degrees at different gravimetric moisture contents. The compacted specimens
were subjected to 100 kPa hydraulic loading with CSG or deionised waters in compaction mould permeameters, and 100 kPa applied
stress in oedometers, with the specimens placed in a bath of CSG or deionised water to match the water used to prepare the
specimens. The 100 kPa loading represented the expected maximum pond water depth. The test results show that the hydraulic
conductivity of clay specimens moisture-conditioned and permeated with both CSG and deionised waters decreased with time due to
rearrangement of the clay particles. At the end of the tests with CSG and deionised waters, the clay specimens were found to have
very low hydraulic conductivities of the order of 1E-11 m/s. The hydraulic conductivity values measured using the compaction mould
permeameters were found to be reasonably comparable to those calculated from oedometer test data.
RÉSUMÉ: Les effets du contrôle en humidité et de l'imprégnation en eau venant de la production du gaz de houille, sur la
conductivité hydraulique des argiles compactées (couramment utilisés pour le revêtement des bassins de stockage de cette eau) sont
étudiés. Quatre argiles majoritairement kaolinites ont été mélangées avec le gaz de houille et de l’eau dé-ionisée, compactés à des
degrés divers et à différentes teneurs en eau gravimétrique. Les échantillons compactés ont été soumis à un chargement hydraulique
de 100 kPa avec le gaz ou l’eau dé-ionisée dans des perméamètres à moules de compactage, à une contrainte appliquée de 100 kPa
dans des œdomètres, les échantillons étant placés dans un bain de gaz ou d'eau dé-ionisée pour correspondre à l'eau utilisée pour
préparer les échantillons. Le chargement de 100 kPa correspondait à la profondeur maximale prévue pour le bassin d'eau. Les résultats
des essais montrent que la conductivité hydraulique des échantillons d'argile à l'humidité contrôlée imprégnés à la fois de gaz de
houille et d’eau dé-ionisée a diminué avec le temps en raison du réarrangement des particules d'argile. A la fin des essais avec le gaz
et l’eau dé-ionisée, les échantillons d'argile ont présentés une très faible conductivité hydraulique de l'ordre de 1E-11 m/s. Les valeurs
de conductivité hydraulique mesurée en utilisant les perméamètres à moules de compactage ont été jugées raisonnablement
comparables à ceux calculés à partir des données de test œdométriques.
KEYWORDS: compacted clay liner, dispersion, hydraulic conductivity, kaolinite, oedometer, compaction mould permeameter.
1 INTRODUCTION
Rigid-wall hydraulic conductivity testing can be carried out
using a compaction mould permeameter or an oedometer. A
compaction mould permeameter allows the direct measurement
of hydraulic conductivity, while hydraulic conductivity is
calculated from the rate of consolidation in an oedometer test
and the values obtained have been found to be too low (e.g.,
Taylor 1942; Mitchell & Madsen 1987).
Natural and compacted clays have been used in Queensland,
Australia, as a liner for the storage of saline water produced
during coal seam gas (CSG) production to limit seepage to the
underlying soil and groundwater. Under the prevailing semi-arid
climatic conditions, the available clays are typically dry and
require moisture conditioning to achieve the moisture content
specified for compaction. The most readily available water for
moisture conditioning is the saline CSG water. This paper
investigates the effects of moisture conditioning and permeating
with CSG water on the hydraulic conductivity of these clays,
with testing using deionised water used as a reference.
2 MATERIALS TESTED
Kaolinite-dominated clay samples, labelled herein as SB1, SB2,
SB3 and DT, were obtained from a CSG production site in
Queensland, Australia. The sand, silt and clay fractions are
shown in Table 1. The liquid limits of SB1, SB2, SB3 and DT
were 64.4%, 44.0%, 61.9% and 65.9%, and the plasticity
indices were 43.6%, 25.2%, 45.2% and 51.1%, respectively.
According to the Unified Soil Classification System (USCS),
SB1 and DT were classified as clays of high plasticity (CH),
SB2 was classified as a sandy clay of low plasticity (CL), and
SB3 was classified as a sandy clay of high plasticity (CH).
Table 1. Particle size distributions of clay samples.
Particle size
Sample
Sand (%)
Silt (%)
Clay (%)
SB1
4.1
26.1
69.8
SB2
26.2
24.7
49.1
SB3
20.6
18.6
60.8
DT
13.3
19.9
66.8
The electrical conductivity (EC) of the saturated paste
extracts, corresponding to about the liquid limits, were
13.4 dS/m, 8.7 dS/m, 14.6 dS/m and 14.6 dS/m, for SB1, SB2,
SB3 and DT, respectively. The exchangeable sodium
percentages were 41.3%, 33.2%, 39.0% and 45.1%,
