Location of Failure Plane within Narrow GRS Wall Systems

The design of a Geosynthetic Reinforced Soil (GRS) wall for internal stability requires computing the reinforcement embedment length against pullout failure. The location of failure plane is important input for this design. The current FHWA design guidelines assume the location of failure plane based on Rankine theory. While this assumption holds true for conventional walls it is unconservative for GRS walls under constrained spaces, also known as “narrow GRS walls”. The observations from centrifuge tests suggest that the inclination angle of failure plane is less than that one calculated based on Rankine theory for narrow GRS walls. This paper presents a limit equilibrium study to accurately locate failure planes within narrow GRS walls. The critical failure planes within narrow GRS walls are searched using Spencer’s method with a function of noncircular failure plane. The results predicted from limit equilibrium analyses shows a good agreement with the experimental data from centrifuge tests conducted on narrow walls. The results indicate that critical failure plane is bilinear: the failure surface being formed partially through the reinforced soil and partially along the interface between the GRS and stable wall faces. Finally, the effect of wall aspect ratio on the inclination angle of the critical failure plane is computed and depicted in a chart for design purposes.