Modeling mechanical response of cemented EPS-backfill

Cemented backfill is one of geomaterials which is used at a high volume to serve a variety of geo-infrastructure systems, e.g., embankments, retaining walls and approach abutments, and involves the solidification of soil or similar fine aggregate through the addition of a controlled amount of cementitious materials, such as Portland cement, fly ash or lime. A certain volume of expanded polystyrene (EPS) pre-puff bead can be incorporated into the backfill matrix to shape the backfill into a mixture, named EPS-backfill, which shows favorable properties a pure backfill rarely exhibits, e.g., reduced unit weight. The ductility of the backfill can also be improved by the inclusion of EPS bead and thus the amendment of material fabric structure. This study was carried out to model the mechanical response of EPS-backfill in terms of the cemented structure of the material. A model was established by treating the shear strength of the material as the combination of bond resistance and friction resistance, which were modeled against elasto-brittle and an elasto-plastic body, respectively. The load share ratio between the two bodies was determined in terms of material breakage undergone by the material. The model was verified against laboratory results of triaxial tests conducted on a series of EPS-backfill samples.