ABSTRACT
When considering the stability with GCLs the bentonite layer has to be regarded as a cohesive soil layer with shear coefficients which depend on the consolidation condition; this means that it has to be differentiated between drained and undrained conditions. The comparably low shear strength of the bentonite layer is overcome by stitch bonding or needle-punching of the geotextile cover and support layers; a transmission of shear forces is made possible by this providing fibre reinforcement. When the shear coefficients are determined in shear tests with GCLs the materials to be used and the actually effective stress and state conditions have to be considered. This paper deals with the long-term shear behaviour on the example of stitch bonded GCLs (strip-wise yarn reinforcement) and needle-punched GCLs (fibre reinforcement over the entire matting) for the use in landfill capping sealing systems.
