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Expanded polystyrene (EPS) geofoam seismic buffers can be used to reduce earthquake-induced loads acting on rigid retaining wall structures. A numerical study was carried out to investigate the influence of wall height; EPS geofoam type, thickness, and stiffness; and excitation record on seismic buffer performance. The numerical simulations were carried out using a verified FLAC code. The influence of parameter values was examined by computing the maximum forces on the walls, the buffer compressive strains, and the relative efficiency of the buffer system. In general, the closer the predominant frequency of excitation to the fundamental frequency of the wall model, the greater the seismic loads and buffer compression. The choice of earthquake record is shown to affect the magnitude of maximum earth force and isolation efficiency. However, when the wall response for walls 3 to 9 m in height are presented in this study in terms of isolation efficiency, the data from scaled accelerograms and matching harmonic records with the same predominant frequency fall within a relatively narrow band when plotted against relative buffer thickness. For the range of parameters investigated, a buffer stiffness value less than 50 MN/m3 was judged to be the practical range for the design of these systems.

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The paper reports the results of six shaking table tests using reduced-scale model walls constructed with expanded polystyrene (EPS) panels to reduce dynamic earth loads due to base shaking. The results are compared with a nominal identical rigid (control) wall constructed without a seismic buffer. The test results show that dynamic load attenuation increased with decreasing geofoam stiffness. The test with the highest buffer stiffness resulted in a 15% reduction in dynamic load and the test with lowest stiffness resulted in a 40% reduction in dynamic load compared with the control wall. The results of these experiments provide proof of the concept that EPS panels placed against rigid walls can act as seismic buffers to attenuate dynamic loads due to ground shaking (e.g. earthquake). Additional quantitative data related to load–deformation–time response, back-calculated elastic modulus values for the EPS seismic buffer configurations, dynamic interface shear properties, acceleration amplification in the backfill soil and post-excitation stress relaxation-creep behaviour are also reported.