Two different constitutive models, an elasto-plastic phenomenological model and a kinematic hardeningisotropic softening plasticity model, have been developed to represent the in plane behavior of geosynthetic barrier layers subject to cyclic loading.
The in-plane behavior of geosynthetic barrier layers subject to cyclic loads is an important consideration in performance based seismic design of waste containment systems, including liner and cover systems for landfills and liner systems for mine site heap leach pads. In-plane behavior of geosynthetic barrier layers includes the interface behavior between geomembranes, geotextiles, and geosynthetic clay liners and waste, soil, or other geosynthetic materials and the internal in-plane behavior of geosynthetic clay liners. Constitutive models for in-plane behavior during cyclic loading are required to predict the stresses, strains, and deformations of the geosynthetic elements of the containment system when subject to seismic loading as well as to predict the seismic response of the overlying waste, soil, or ore mass. Both of the constitutive models described herein are capable of modeling a post-peak decrease in mobilized in-plane shear strength and degradation in the inplane mobilized shear resistance during uniform cyclic loading. Both constitutive models have been implemented in a large strain finite difference numerical model and are shown to be able to predict typical patterns of behavior for the in-plane behavior of geosynthetic barrier layers subject to uniform cyclic loading.