Reliability-based design of internal limit states for mechanically stabilized earth walls using geosynthetic reinforcement

Abstract

This paper demonstrates reliability-based design for tensile rupture and pullout limit states for mechanically stabilized earth (MSE) walls constructed with geosynthetic (geogrid) reinforcement. The general approach considers the accuracy of the load and resistance models that appear in each limit state equation plus uncertainty due to the confidence (level of understanding) of the designer at the time of design. The reliability index is computed using a closed-form solution that is easily implemented in a spreadsheet. The general approach provides a quantitative link between nominal factor of safety, which is familiar in allowable stress design practice, and reliability index used in modern civil engineering reliability-based design practice. A well-documented MSE wall case study is used to demonstrate the general approach and to compare margins of safety using different load and resistance model combinations. A practical outcome from the case study example is the observation that the pullout limit state is much less likely to control design than the ultimate tensile rupture state for walls with continuous reinforcement coverage. The more accurate “simplified stiffness method” that is used to compute tensile loads in the reinforcement under operational conditions is shown to generate a more cost-effective reinforcement option than the less accurate American Association of State Highway and Transportation Officials (AASHTO) simplified method.

FEM model for analysing the interaction of a geomatrix with a subsoil

“…Since the geosynthetic in a geomatrix transfers tensile stress, it is often believed that it creates a reinforcement, and the entire geomatrix is viewed as a structure from reinforced soil. However, this is not true, because the main task of the geosynthetic is to immobilize (stabilize) the aggregate grains, thanks to which the layer thus formed will provide proper reinforcement of the subsoil and an appropriate support for the structure being built [10], [28]. The most important feature of the geomatrix is its high stiffness, which ensures the correct construction of an object located directly on it (works are carried out on a stable subsoil).…”

2020 Awards

“…R.J. Bathurst, P. Lin, and T. Allen: Reliability-based design of internal limit states for mechanically stabilized earth walls using geosynthetic reinforcement (Bathurst et al 2019) ABSTRACT: This paper demonstrates reliability-based design for tensile rupture and pullout limit states for mechanically stabilized earth (MSE) walls constructed with geosynthetic (geogrid) reinforcement. The general approach considers the accuracy of the load and resistance models that appear in each limit state equation plus uncertainty due to the confidence (level of understanding) of the designer at the time of design.…”