Shear strength characteristics of interlocked EPS-block geofoam-sand interface

Abstract

Translation of entire geofoam embankment at the bottom of geofoam block assemblage and bedding sand is a possible internal failure mode due to unbalanced hydrostatic forces. In addition, available shearing resistance along the bottom of geofoam block assemblage and bedding sand is an important design issue for internal seismic stability analysis. This study has focused on the methods to increase the interface shear resistance along the traditional flat surface geofoam block and bedding sand interface. In addition to traditional flat surface geofoam-sand interface, the effect of four different interlock configurations composed of geofoam blocks with one- and four-triangular and one- and four-square ledges were quantified by using direct shear tests. Two different densities (EPS19 and EPS29) and two different types of sand (Ottawa sand and Adapazari sand) were used. Therefore, the effects of geofoam stiffness, interface geometry, grain size and particle shape of the bedding sand on the interface stress-strain behavior was quantified. Manufacturing ledges along the traditional geofoam surface significantly improved the geofoam block-sand interface shear resistance. In addition, interrupting the failure plane with ledges changed the interface shear mechanism of the traditional flat surface geofoam block-bedding sand interface from purely frictional to frictional-cohesive behavior.