Abstract: Various stress-controlled drained and undrained monotonic shear tests on the Chinese Fujian standard sand of relative density 30 % under complex initial consolidation conditions with different stress paths are conducted by using the soil static and dynamic universal triaxial and torsional shear apparatus. The average principal stress is unchanged in the process of tests. The coefficient of intermediate principal stress and orientation of principal stress are changed so that their influences on shear behaviors of saturated sands under different drainage conditions are respectively probed. It is shown by comparison that coefficient of intermediate principal stress influences the stress-strain normalization relationship, but does not have obvious effect on volumetric deformation as well as pore-water pressure. Under the same initial condition, the deviator stress ratio decreases with the increase in coefficient of intermediate principal stress. The above-mentioned phenomena do not relate to the drainage condition. Orientation of principal stress also has remarkable influence on monotonic shear features of sands. In drained tests, variation pattern of stress-strain relationship which is associated with the orientation of principal stress depends on shear stresses on horizontal plane and vertical plane. In undrained tests, the effective deviator stress ratio attained at peak state decreases gradually with the increase in orientation angle of principal stress.

Key words: monotonic shearing, coefficient of intermediate principal stress, orientation of principal stress, phase transformation state, peak state, effective deviator stress ratio