Framework for Limit State Design of Geosynthetic-Reinforced Walls and Slopes

Abstract

Introduced is a unified limit state design framework for geosynthetic-reinforced slopes and walls. It is demonstrated that limit state design is an essential step in design even though the usual perception is that the performance of such structures is “better than expected.” A brief critical overview of commonly available analysis methods is presented. The typical design methodology which is an extension of conventional limit equilibrium (LE) analysis is discussed. It is shown that with the addition of the safety map tool, an optimized design can be achieved with relative ease. However, while the safety map can be used in design, the basic solution is still incomplete. Subsequently, the LE approach is generalized to include the complete solution, i.e., the required tensile force distribution along each layer considering reinforcement layout and anchorage properties. The modified approach produces a solution needed for stability including the required connection strength. It is based on free body equilibrium ensuring that at each point within the reinforced mass, the factor of safety is the same. That is, unlike the safety map which shows the corresponding safety factor at each location, the presented framework adjusts the required strength of the reinforcement so that the safety factor is the same constant everywhere. Limited parametric studies demonstrate the performance of the new framework as well as that of the safety map approach. These studies show the impact of facing blocks, seismicity, backslope, quality of backfill, length of reinforcement, and effects of secondary short reinforcement. The results are compared with relevant experimental data. The agreement is reasonably good. Finally, a general link between the framework and actual design is briefly discussed.