Using the soil static and dynamic universal triaxial and torsional shear apparatus

a series of undrained monotonic shear tests are performed for saturated Fujian standard sands with a relative density of 30%.The mean consolidation stress and the coefficients of the intermediate principal stress are invariable while the orientation of principal stress is variable in the proceeding of tests.By contrasting with the monotonic shear test results under the condition that the orientation of principal stress is invariable

it is concluded that when the saturated sand sample has horizontal sedimentary plane

the different combinations of initial orientation of major principal stress and direction of monotonic shearing make the actual orientation of major principal stress different during the shearing

which affecting the undrained monotonic shearing behavior of sand remarkably.The actual orientation of major principal stress is the most essential factor which affects the undrained monotonic shearing behavior of the saturated sand.