Reliability of state of practice for selection of shear strength parameters for waste containment system stability analyses

Abstract

In this paper, reliability analyses are performed using the results of slope stability analyses on example waste slopes to address two sources of uncertainty involved in waste slope stability assessments. These include the uncertainty associated with using shear strength parameters derived from non-project-specific sources and the uncertainty associated with the conditions required to make the development of a progressive failure mechanism, and subsequent mobilization of large-displacement shear strengths, possible. The results of the slope stability and reliability analyses performed demonstrate that less reliable or overly conservative designs can result from the use of shear strength parameters obtained from non-project-specific sources and that reliability analyses, even simple ones, provide information that can be used to establish confidence levels in factor of safety calculations. Reliability analysis results also show that slope stability calculations based on the full mobilization of large-displacement shear strengths are conservative since such analyses implicitly assume that a progressive failure mechanism develops. A method is presented that considers one particular progressive failure mechanism for the development of large-displacement conditions. The method provides a framework for evaluating the reliability of slopes where the potential for progressive failure exists.