Abstract: Calcareous sand is a geotechnical material formed after the death of marine calcareous organisms with abundant internal pores, low strength, irregular shape and easy fragility. In this study, the mechanical and deformation characteristics of calcareous sand under different stress paths were investigated through five tests of isotropic compression, conventional triaxial compression, triaxial compression with constant average principal stress, triaxial compression with reduced compression, and constant stress ratio loading on calcareous sand. The results indicated that the stress path notably affected the shear strength and deformation characteristics of calcareous sand. Calcareous sand had obvious anisotropic properties under isotropic compression. In the conventional triaxial compression test, dense calcareous sand presented the deformation characteristics of low-pressure dilatancy and high-pressure contraction, and there existed a power function relationship between the peak strength and the initial consolidation pressure. Increasing deviatoric stress could cause a volumetric strain of the specimen under the triaxial compression condition with constant average principal stress. Unlike the conventional triaxial compression test, the stress-strain relationship curves in the triaxial compression test with reduced compression presented strain softening. In the constant stress ratio loading test, the specimen was basically in the elastic state, and the relationship between the axial stress and the axial strain was a power function. The experimental results also indicated that the tangential Poisson’s ratio of calcareous sand was not only dependent on the deformation and stress state of calcareous sand, but also influenced by the stress path. The order of magnitude in the peak stress ratio and the maximum volumetric strain under different stress path tests were not affected by the initial consolidation pressure. The peak internal friction angle of calcareous sand decreased with the increase of the initial consolidation pressure, roughly as a linear function of the logarithm of the initial consolidation pressure.

Key words: stress path, calcareous sand, shear strength, deformation, triaxial test