Effect of boundary conditions on earth pressure reduction using EPS Geofoam

Abstract

This paper presents results of small scale physical model tests on an instrumented rigid retaining wall subjected to 1-D shaking and effectiveness of EPS (expanded polystyrene) geofoam to reduce seismic earth pressures. Two different boundary conditions viz., retaining wall with and without hinge at the base were considered during experiments. Initial application of 50 kPa static surcharge, followed by seismic load in the form of a stepped sinusoidal acceleration in the range of 0 to 0.7 g was applied in increments of 0.045 g, each increment being applied for 5 seconds at 3 Hz frequency. The seismic earth pressure distribution was observed nearly hydrostatic in the case of retaining wall with hinge, without geofoam inclusion. Whereas, for the retaining wall without hinge, the observed seismic earth pressure distribution was curvilinear with maximum pressures in the upper half of the retaining wall. Provision of 10D (10 kg/m3) EPS geofoam reduced the total lateral force on the retaining wall by about 23% and 28%, for retaining wall with and without hinge, respectively. It was observed that, boundary conditions are mainly influenced the earth pressure distribution in both the cases, with and without geofoam provision.