Abstract: In order to research a new type of geotechnical material——light weight sand, its deformation and strength characteristics were researched by triaxial test. The results show that light weight sand have different primary structural strength because of different mixed ratio and age, soil samples of different primary structural strength are in the state of shear dilatancy or shear contraction under different confining pressures, these lead to strain hardening, strain softening, and three corresponding pore pressure states. Deformation modulus decreases linearly with increase of EPS(expanded polystyrene beads) mixed ratio, increases linearly with increase of cement mixed ratio and age; and there is little relation between deformation modulus and confining pressure for the same mixed ratio soil samples. Triaxial compressive strength decreases according to negative exponential relation with increase of EPS mixed ratio, increases linearly with increase of cement mixed ratio, age and confining pressure. There is a threshold for cement mixed ratio. Transformation effect of soil framework has an important effect on soil strength, and that leads to strength zoning under uniaxial and triaxial compression states. When cement mixed ratio reaches to a high value, it can weaken transformation effect of soil framework of EPS beads. Combining precursors’ research production, influence factors of density and uniaxial compressive strength of light weight sand are researched; then the concept of specific strength is recommended. Prescription of light weight soil-sand can be optimized by combining unit price-specific strength figure and recipe formula. Stress-strain relation transformation of light weight soil-sand is researched, uniaxial compressive strength is recommended to be metewand of primary structural strength. The relation between critical confining pressure and primary structural strength should be built according to test and mathematical statistics; these can make contribution for numerical simulation and establishment of constitutive model.

Key words: light weight sand, deformation modulus, compression strength, stress-strain relation transformation, primary structural strength, specific strength