Interface transmissivity and hydraulic conductivity of GCLs below poured concrete

ABSTRACT: The performance of four geosynthetic clay liners (GCLs) used as a hydraulic barrier below concrete-lined sewage treatment lagoons was examined based on a series of laboratory tests aimed at measuring: (i) the lateral flow of synthetic wastewater through the interface between each GCL product and a 0.1 m thick cast-in-place concrete above the GCL over a 14-month period and, from this data, calculating the concrete/GCL interface transmissivity (θ); and (ii) the hydraulic conductivity (k) of the GCLs below poured concrete when exposed to (iia) synthetic wastewater under isothermal conditions, or (iib) a series of wet–dry and/or cool–heat cycles for up to 12 months. The four GCLs have either sodium or polymer-enhanced sodium bentonite, and either granular or powdered bentonite. When the wastewater head above the GCL was 1.0 m (stress on concrete, σ = 10 kPa), θ for the GCL with granular sodium bentonite was 4 × 10−11 m2/s. For the same GCL, when the head increased to 2.5 m (σ = 25 kPa), the value of...