Hydraulic performance of geosynthetic clay liners in a landfill final cover

Craig H. Benson, Patricia A. Thorstad, Ho Young Jo, Steven A. Rock

Research output: Contribution to journalArticle

70 Citations (Scopus)

Abstract

Percolation from a landfill final cover containing a geosynthetic clay liner (GCL) as the hydraulic barrier is described. The GCL was covered with 760mm of vegetated silty sand and underlain with two gravel-filled lysimeters to monitor percolation from the base of the cover. Higher than anticipated percolation rates were recorded in both lysimeters within 4-15months after installation of the GCL. The GCL was subsequently replaced with a GCL laminated with a polyethylene geofilm on one surface (a "composite" GCL). The composite GCL was installed in two ways, with the geofilm oriented upwards or downwards. Low percolation rates (2.6-4.1mm/year) have been transmitted from the composite GCL for more than 5years regardless of the orientation of the geofilm. Samples of the conventional GCL that were exhumed from the cover ultimately had hydraulic conductivities on the order of 5×10-5cm/s. These high hydraulic conductivities apparently were caused by exchange of Ca and Mg for Na on the bentonite combined with dehydration. The overlying and underlying soils likely were the source of the Ca and Mg involved in the exchange. Column experiments and numerical modeling indicated that plant roots and hydraulic anomalies caused by the lysimeters were not responsible for the high hydraulic conductivity of the GCL. Despite reports by others, the findings of this study indicate that a surface layer 760mm thick is unlikely to protect conventional GCLs from damage caused by cation exchange and dehydration. Accordingly, GCLs should be used in final covers with caution unless if cation exchange and dehydration can be prevented or another barrier layer is present (geomembrane or geofilm).

Original languageEnglish
Pages (from-to)814-827
Number of pages14
JournalJournal of Geotechnical and Geoenvironmental Engineering
Volume133
Issue number7
DOIs
Publication statusPublished - 2007 Jul 1

Fingerprint

clay liner
geosynthetics
Land fill
landfill
Clay
Hydraulics
hydraulics
Lysimeters
Hydraulic conductivity
lysimeter
Dehydration
dehydration
hydraulic conductivity
ion exchange
Ion exchange
Composite materials
Positive ions
Geomembranes
geomembrane
Bentonite

Keywords

  • Clay liners
  • Dewatering
  • Geosynthetics
  • Hydraulic conductivity
  • Landfills

ASJC Scopus subject areas

  • Environmental Science(all)
  • Geotechnical Engineering and Engineering Geology

Cite this

Hydraulic performance of geosynthetic clay liners in a landfill final cover. / Benson, Craig H.; Thorstad, Patricia A.; Jo, Ho Young; Rock, Steven A.

In: Journal of Geotechnical and Geoenvironmental Engineering, Vol. 133, No. 7, 01.07.2007, p. 814-827.

Research output: Contribution to journalArticle

Benson, Craig H. ; Thorstad, Patricia A. ; Jo, Ho Young ; Rock, Steven A. / Hydraulic performance of geosynthetic clay liners in a landfill final cover. In: Journal of Geotechnical and Geoenvironmental Engineering. 2007 ; Vol. 133, No. 7. pp. 814-827.
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