Performance of Geosynthetic Reinforced Slopes at Failure

Abstract

A centrifuge testing program was undertaken to investigate the failure mechanisms of geosynthetic reinforced soil slopes and to evaluate the assumptions in their design. Scaling laws were established so that factors of safety in the models would be identical to those in prototype structures. Failure of the models was characterized by well-defined shear surfaces through the toe of the slopes, which is in good agreement with current design methods for reinforced slopes based on limit equilibrium. The moment of failure was defined by a sudden change in the rate of settlements at the crest of the slope. In contrast to the assumption in current design procedures that failure should initiate at the toe of a reinforced slope, failure initiated at midheight of the slopes. Model deformations were found to depend on the backfill properties, but were essentially independent of the tensile strength and spacing of the reinforcements. The test results showed that overlapping reinforcement layers contribute to stability as they failed by breakage instead of by pullout when intersected by the failure surfaces. The experimental results also indicate that stability of the reinforced slopes is governed by the peak shear strength and not by the critical state shear strength of the backfill soil. A new distribution of maximum reinforcement forces with depth, which is consistent with the failure mechanism observed in the models, is proposed for geosynthetic reinforced soil slopes.

Peak Versus Residual Shear Strength in Geosynthetic-Reinforced Soil Design

“…A detailed description of the characteristics of the centrifuge testing program is presented by Zornberg et al (1998a). The centrifuge tests can be grouped into three test series (B, D, or S).…”

“…This has led to a perceived overconservatism in their design. Consequently, an investigation was undertaken to evaluate design assumptions for geosynthetic-reinforced slopes (Zornberg et al 1998a(Zornberg et al , 2000. The results of centrifuge tests provide an excellent opportunity to examine the validity of various assumptions typically made in the analysis and design of reinforced soil slopes.…”

“…0 sand obtained by Riemer (1992). As the residual friction angle is mainly a function of mineralogy (Bolton 1986 Scale requirements for the reinforcing material establish that the reinforcement tensile strength in the models should be reduced by N. That is, an Nth-scale reinforced slope model should be built using planar reinforcement having 1/N the strength of the prototype reinforcement elements (Zornberg et al 1998a). Two types of nonwoven interfacing fabrics, having mass per unit area values of 24.5 and 28 g/m 2 , were selected as reinforcement.…”

Short communication: (What) To teach or not to teach – from theory to practice

“…This is not sensible, partly because the value of f 0 cv cannot be measured with clays, since it lies at an indeterminate value between the peak and the residual value and partly because soil failure is governed by the peak value of f 0 . Zornberg et al (1998), for example, conclude from their experimental testing of reinforced earth walls that failure is governed by the peak f 0 value.…”

Numerical Analysis on Deformation Behavior of Geosynthetic-Reinforced Slopes

“…Some valuable work associated with such analysis has been conducted by Jewell, 1982Jewell, , 1986Jewell, and 1991Milligan and Rochelle, 1984;Rowe and Soderman, 1985;Leshchinsky and Reinschmidt, 1985;Leshchinsky et al 1986;Hird, 1986;Chouery et al, 1989;Leshchinsky and Boedeker, 1989;Koerner, 1990;Low et al, 1990;Greenwood, 1990;Mandal and Labhane, 1991;Wright and Duncan, 1991;Greenwood and Zytynski 1993;Sabhahit et al, 1994;Leshchinsky et al 1995;Mandal and Joshi, 1996;Low and Tang, 1997;Palmeira et al, 1998;Shahgholi et al 2001. Centrifuge model tests have been conducted by Zornberg et al (1998Zornberg et al ( & 2003, Viswanadham and Mahajan (2007) to investigate the mechanical behaviour of reinforced slopes both at failure and in pre-failure states.…”