The Effect of Amplification on the Seismic Stability of Reinforced Soil Slopes Using Horizontal Slice Method

Horizontal Slice Method (HSM) is an approach employed to evaluate the seismic stability of soil slopes and walls in the framework of limit equilibrium method and pseudo-static analysis. HSM is also capable of applying variable accelerations at different levels within the horizontal slices of a slope or retaining structure, which is difficult when using other limit equilibrium procedures. In this paper the effect of amplification of seismic acceleration on the stability of slopes and soil structures has been evaluated. In combination with the HSM a pseudo-dynamic method is adopted in the present analysis, which also considers the effect of phase difference in the shear waves traveling through the backfill due to seismic excitation. The analysis is based on the observations of Nova-Roessig and Sitar relating to centrifuge tests performed on a number of scaled reinforced soil slopes. Two main sets of analyses are conducted. In the first one, seismic amplification is considered in the analysis by assigning amplified accelerations at different levels to the corresponding slices with different distributions. The second set of analyses is conducted for slopes having the same seismic acceleration for all the slices, which means there is no amplification. The main results of the analysis are presented in dimensionless form relating to the total force in the reinforcement layers to maintain the stability of the reinforced structure. This definition is equivalent to the coefficient of active lateral earth pressure. Therefore the effect of amplification on the active lateral earth pressure can be evaluated and compared with the case of no amplification. The failure surfaces for each set of analysis are also obtained and compared with the observed deformations in the physical model.