Reliability-based stability analysis considering GCL shear strength variability

Abstract

The impact of different levels of uncertainty in geosynthetic clay liner (GCL) shear strength on landfill stability is evaluated in this study. The uncertainty in shear strength of the interface governing landfill stability is defined using statistical parameters obtained from a significant database of GCL internal and GCL–geomembrane interface large-scale direct shear tests. Uncertainty in GCL shear strength arises from material variability within a single product type and between different product types. For a given product type, uncertainty arises from material differences among specimens from the same manufacturing lot as well as among specimens from different manufacturing lots. In addition, uncertainty was observed to arise from differences in test procedures such as hydration, consolidation and shear displacement rate. A framework for incorporating the observed laboratory shear strength variability into realistic field applications is presented. Reliability-based stability analyses were used to assess the impact of uncertainty in laboratory GCL shear strength test results on conventional design methodologies. Specifically, the impact of uncertainty on the relationships between the conventional safety factor and the probability of failure is assessed. Owing to the high shear strength variability observed in the database, high probability of failure values were found to correspond to safety factors typically used in geotechnical practice.