Keywords: seismic slope stability, geosynthetics, soil reinforcement, sliding, coupled SDOF models, finite element analyses.

Over recent decades increased research interest has been observed on the dynamic response and stability issues of earth walls and reinforced soil structures [1]. The current study aims to provide an insight into the dynamic response of reinforced soil structures and the potential of the geosynthetics to prevent the development of slope instability taking advantage of their reinforcing effect. The seismic response of reinforced soil slopes was investigated focusing on the evaluation of instability in terms of permanent slip displacements. For this purpose, a two-dimensional finite-element simulation and a coupled SDOF semi-analytical model were formulated [2,3], which were subsequently used to calculate the magnitude of slip displacements. The coupled dynamic time history analyses which were performed took into account the flexibility of the sliding system, the mechanical properties of the soil and of the geosynthetic material. The general trends observed in the numerical results agree qualitatively with the corresponding ones derived from a series of geotechnical centrifuge tests of a previous study.

It is evident from the results that, as expected, the assumptions of traditional limit equilibrium-based seismic design methods are not supported by the findings of the experimental and the numerical investigations. In general, pseudo-static analyses cannot simulate the extensive (non-discrete) failure surfaces that develop in reinforced soil slopes and cannot estimate displacements. The critical failure surface predicted by pseudo-static analyses approximates only the region of significant deformations. In contrast, permanent deformation analyses can provide a realistic estimate of the developed displacements, but do not provide a distribution along the height of the earth structure. On the other hand, numerical methods (FE-based) can alleviate the deficiencies of the other two approaches, but provide satisfactory results only when proper interface simulation and advanced constitutive material modelling are used, which are not readily available. The application of the two numerical approaches has illustrated the advantages and the shortcomings of each methodology.

1

L.M. Nova-Roessig, N. Sitar, "Centrifuge studies of the seismic performance of reinforced soil structures", Report No. UCB/GT/99-13, Dept. Civil Engineering and Environmental Engineering, University of California, Berkeley, USA, 1999.

2

N.M. Newmark, "Effect of earthquakes on dams and embankments", Geotechnique, 15(2), 139-160, 1965. doi:10.1680/geot.1965.15.2.139

3

B. Westermo, F. Udwadia, "Periodic response of a sliding oscillator system to harmonic excitation", Earthquake Engineering and Structural Dynamics, 11, 135-146, 1983. doi:10.1002/eqe.4290110111

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