Abstract
In practical engineering, if the influence of noncoaxial stress and strain is not considered, part of soil deformation will be ignored, resulting in the structural design which is not safe enough. A series of undrained tests was performed on remolded loess specimens using a hollow cylinder apparatus to examine the coupling between principal stress magnitude and direction in these specimens. First, the elastic parameters of remolded loess were obtained, and these parameters were used as the basis for investigating the noncoaxiality of the soil body under principal stress axis rotation (PSAR). The effects of elastic strain, intermediate principal stress coefficient, and magnitude of the deviatoric stress on the noncoaxiality of remolded loess were also investigated. The results of these experiments show that remolded loess exhibits significant noncoaxial behavior during PSAR. The noncoaxiality angle of remolded loess cyclically fluctuates with increases in the principal stress angle. It was also observed that the noncoaxiality angle will be overestimated if the effects of elastic strain are overlooked. Reversals in the direction of PSAR cause dramatic changes in the noncoaxiality angle. Increases in the intermediate principal stress coefficient are accompanied by increases in the noncoaxiality angle, up to a certain degree; however, these changes do not affect the development of the noncoaxiality angle. In coupled rotational tests with a range of deviatoric stress amplitudes, it was observed that changes in the deviatoric stress amplitude will affect the development of the noncoaxiality angle; increases in the deviatoric stress amplitude cause the noncoaxiality angle versus principle stress angle plot to shift to the left gradually, thus accelerating the trends of the noncoaxiality angle. Increases in the cycle number also increase the noncoaxiality of remolded loess.
Highlights
The structural load always changes in a reciprocating cycle, such as vehicle load and wave load, and the direction of large principal stress will change from the horizontal direction to vertical direction and, to the horizontal direction from far and near. e magnitude, direction, and frequency of stress are different, showing different engineering characteristics. e principal stress cyclic rotation test with research direction and size coupling is important for engineering safety significance
It was observed that the effects of soil compaction on the noncoaxiality angle are significant under low shear stresses, but insignificant under high shear stresses
Based on principal strain axis rotation (PSAR) stress paths, we investigated the development of elastic strains in remolded loess. e effects of elastic strain, intermediate principal stress coefficient (b), deviatoric stress amplitude (∆q), and the number of cycles on the noncoaxiality of remolded loess were investigated, in addition to the underlying mechanisms of these effects
Summary
The structural load always changes in a reciprocating cycle, such as vehicle load and wave load, and the direction of large principal stress will change from the horizontal direction to vertical direction and, to the horizontal direction from far and near. e magnitude, direction, and frequency of stress are different, showing different engineering characteristics. e principal stress cyclic rotation test with research direction and size coupling is important for engineering safety significance. Liu et al [7] observed significant degrees of noncoaxiality in the stress-strain relationships of K0-consolidated saturated silt based on triaxial directional shear tests on these soils using a GDS triaxial apparatus. It was observed that the undisturbed and remolded soil specimens display similar noncoaxial fluctuations, but the effects of noncoaxiality were amplified by the intrinsic anisotropy of the undisturbed specimen On this basis, they proposed a model for the plastic flow of soft clay that accounts for noncoaxiality. The elastic parameters of remolded loess were obtained by performing coupled principal stress amplitude-PSAR tests with repeated cyclic loads on remolded loess in undrained conditions. E effects of elastic strain, intermediate principal stress coefficient (b), deviatoric stress amplitude (∆q), and the number of cycles on the noncoaxiality of remolded loess were investigated, in addition to the underlying mechanisms of these effects. A noncoaxial constitutive model was constructed for saturated loess, providing an experimental reference for future studies about the deformation characteristics of saturated loess under PSAR
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