Reliability Assessment of Internal Stability Limit States for Two As-Built Geosynthetic MSE Walls

Abstract

This paper reports the results of calculations for the margins of safety for internal stability limit states for two as-built geosynthetic MSE walls constructed in 2006 in Washington State, U.S.A. The walls are unique because a) the internal stability design for the reinforcement was based on a working stress design method which includes the stiffness of the reinforcement as a key parameter, and b) the walls were instrumented and monitored during and after construction. Margins of safety are quantified deterministically using factors of safety, and probabilistically using reliability indices. The calculations are performed using the properties of the as-built materials as opposed to the properties assumed at the time of original design. The results show that the margins of safety for tensile and pullout strength are huge and thus these limit states are not of practical concern for these structures. The critical limit state is the soil failure limit state. Margins of safety for this limit state are shown to be closer to recommended minimums but nevertheless adequate for all reinforcement layers in both walls.