Swelling and diffusion characteristics of the experimental GCLs

Swelling and diffusion characteristics of GCL samples made in the laboratory were studied and the results compared with the results of an industrial GCL. A Swell-Diffusion apparatus was designed, fabricated, and used to perform the swelling and swelling-diffusion tests. Two types of available local geotextiles (Types I and II) with an available low quality Bentonite (LQB) were used to fabricate two types of GCL’s in the laboratory (Types A and B E-GCLs). The effect of stitching, applied stress, and wetting procedure, was investigated in swelling tests. For type A E-GCL, with no stitch and no applied stress, a maximum of 6 mm swell was observed. Under 12.5 kPa stress, the swell decreased to a maximum of 2 mm. When this GCL was stitched, a maximum of 1.8 mm and 1.4 mm swell with zero and 12.5 kPa stresses were shown, respectively. The swelling results showed that the wetting procedure (from top, from bottom, and both ways) has a negligible effect in maximum swell. The type B E-GCL (having better geotextile quality compared to type A) showed a maximum 2.3 mm swell with no stitch, and 1.6 mm swell when stitched. The industrial needle punched reinforced GCLs with high quality granular sodium bentonite, under 12.5 kPa stress and wetted from top and bottom, showed a maximum of 3 mm swell. The swell data obtained from these experiments are in reasonable agreement with the data reported in the literature for similar GCLs under comparable conditions. Diffusion experiments were performed for types A and B E-GCL’s, as well as for the industrial GCLs. The chloride diffusion coefficients for types A and B E-GCL’s ranged from 2.7x10-10 m2/s to 3.5x10-10 m2/s compared to 2.9x10-10 m2/s to 3.5x10-10 m2/s for the industrial GCLs, which is in good agreement.