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Paper title: Geosynthetic Clay Liner Overlap Performance and Testing

Authors - Preston Kendall, John Buckley and Richard Austin


Whilst the hydraulic performance of Geosynthetic Clay Liners (GCLs) is rigorously tested, the performance of the overlap is equally important, frequently untested and poses additional testing challenges.  

Designers should be confident that overlap performance is equivalent or superior to that of the constituent GCL, otherwise the overlap is introducing a weakness into the design of the lining system. Overlap performance however is often not specified in standard GCL QA regimes and there is little published data on the overlap performance of the various recommended practices.

Geofabrics tested a range of GCLs for overlap performance compared to the constituent GCL.  Results show that additional treatment of overlaps is necessary to match the hydraulic performance of constituent GCL.  Effective overlapping systems include the application of bentonite paste as well as bentonite powder impregnated in the overlap area.

The paper outlines a practical test method to measure GCL overlap performance, discusses the measured performance of different overlap construction techniques and suggests ways to optimise GCL field overlap performance.  

For more information on how to design or specify geosynthetic clay liners, including the overlap detail, please contact Preston Kendall on 07 5594 8600 or at This e-mail address is being protected from spambots. You need JavaScript enabled to view it

I would like more info.

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