geosynthetic clay liners

The di!usion coe$cients deduced from GCL di!usion tests performed with 3 g/L to 5 g/L (0.05 M to 0.08 M) NaCl solutions decrease linearly with decreasing "nal bulk GCL void ratio. However, this di!usion coe$cient is shown to be dependent on the source solution and, when the NaCl concentration is increased signi"cantly, the di!usion coe$cient deduced is also shown to increase. For the range of products examined, it is shown that the method of GCL manufacture did not signi"cantly a!ect the di!usion coe$cients. Di!erent methods of perform-ing the test are examined and it is shown that the type of di!usion test has little e!ect on the di!usion coe$cient deduced at a given void ratio for the range of NaCl concentrations examined (3 g/L to 5 g/L). However, as the NaCl concentration increases to 0.6 M or 2.0 M, a constant stress applied to the sample is shown to mitigate increases in di!usion coe$cients compared to the case of the sample being tested at a constant void ratio. ( 2000 Elsevie