Permeability of damaged geosynthetic clay liners

The results of an experimental test program for the permeability of a damag ed, adhesive-bonded, geosynthetic clay liner (GCL) are presented. GCL speci mens were damaged to simulate damage occurring during handling or installat ion. Either a portion of the GCL was removed to simulate tearing with bento nite loss, or the GCL was punctured with a metal object to simulate damage without bentonite loss. In general, positive results were obtained for the case of damage with bentonite loss: holes up to 3 cm in diameter self-heale d with only a slight increase in hydraulic conductivity compared to an inta ct GCL. However, the self-healing process can be compromised if torn GCLs w ith bentonite loss are placed on a coarse subgrade with large pore openings , which allows the bentonite to migrate from the puncture in the GCL. Damag e without bentonite loss was simulated for both hydrated and unhydrated GCL specimens. Complete self-healing of punctures was generally obtained, but it was also shown that the conversion of sodium bentonite to calcium benton ite causes a drastic reduction of the self-healing capacity of the GCL, con firming that ion exchange is particularly harmful to the overall performanc e of GCLs.