Interface Shear Strength Characteristics of Interlocked EPS-Block Geofoam

Abstract

Lightweight fills constructed by the use of expanded polystyrene block (EPS-block) geofoam (geofoam block) is known to be susceptible to horizontal loading since the vertical pressure which enhances the shear resistance along the interface of individual blocks is low. Therefore, research has focused on the methods to increase the interface shear resistance of geofoam blocks. This study investigated the use of interlocking mechanisms by conducting direct shear tests on four different interlock configurations. An interlock configuration utilized a number of ledges and notches to interrupt the continuous horizontal shearing plane in-between geofoam blocks. Two different densities of geofoam blocks (EPS19 with a minimum density of 18.4 kg/m3 and EPS29 with a minimum density of 28.8 kg/m3) were used in order to investigate the effect of material hardness on stress-strain behavior and interface friction properties. The results of this study showed that the interlocking mechanism improved the interface shearing resistance of geofoam blocks. The number of ledges and notches used in an interlocked configuration had an effect on the interface shear strength properties, and higher numbers raised the interface failure envelope to the level of internal shear strength of monoblock EPS. In conclusion, implementing an interlocked configuration changed the EPS/EPS interface friction mechanism from purely frictional to frictional-adhesional.