Abstract: Lightweight fills of sand-EPS beads were formed by blending sands with EPS beads in proportions.They could be used as lightweight geomaterials/fills suitable for various infrastructures,e.g.,embankments,backfills and replacing materials.To study their deformation and shear strength behavior could help understand their mechanical properties and determine the ground deformation and stability in the fields.A laboratory investigation was conducted to disclose the compression deformation,shear deformation and strength behaviors of the lightweight fills of sand-EPS beads.One-dimensional(1D) compression tests and consolidated drained triaxial shear tests were implemented.Based on the 1D compression tests,a compression model was proposed to describe their compression deformation behavior and to consider the solid phase volumetric variations.In triaxial shear tests,deviatoric stress-axial strain-volumetric strain curves and K f lines were observed.Effects of mixing ratios and stress conditions on the shear deformation and strength behaviors were also discussed.Meanwhile,transition points along Kf lines were analyzed,which would help determine the mixing ratios.