Global Stability of Bilinear Reinforced Slopes

Abstract

Design and construction of geosynthetic reinforced simple slopes are a common practice. These types of slope commonly use a single inclination, termed a linear slope. Design of linear slopes is frequently done using limit equilibrium (LE) analysis. The scenario of two tiered slopes, one with a vertical upper tier and another with an inclined lower tier, is termed in this study as a bilinear slope. It increases the right-of-way for various types of infrastructure in the same way as linear slopes. This paper presents a LE approach to analyze such bilinear reinforced slopes. This LE analysis uses a top-down log spiral mechanism and is rigorous in the sense that it satisfies equilibrium at the limit state. The presented formulation and numerical scheme yield the required, unfactored reinforcement strength. Results are presented in the form of stability charts, enabling quick assessment of reinforcement strength required for stability. A complementary chart shows the quantity of backfill saved when using bilinear reinforced slope versus the alternative, equivalent linear reinforced slope. A shallow inclination of the lower tier eliminates the need for its reinforcements although it is surcharged by a vertically reinforced slope. That is, the reinforcement in the upper tier also resists failures through its foundation, an aspect that is considered in the analysis. However, if the lower tier is steep, it may require some reinforcement as the resistance of the geosynthetics placed in the upper tier is not sufficient for adequate stability.