Behavior of Saturated Remolded Loess Subjected to Coupled Change of the Magnitude and Direction of Principal Stress

Abstract

Undrained torsional shear tests were carried out on remolded loess specimens using a hollow cylinder apparatus to investigate the deformation behavior and noncoaxiality (where the direction of the plastic strain increment is not coaxial with the direction of the principal stress) of remodeled loess when the magnitude and direction of the principal stress change simultaneously. It can be found that the deformation behavior of tested samples is significantly influenced by the intermediate principal stress coefficient and the rotation range of the principal stress. The influences of elastic strain, rotation range of principal stress, intermediate principal stress coefficient, and cycle period on the noncoaxiality were also studied. Analysis of the test results demonstrate obvious noncoaxiality of the remolded loess. The noncoaxiality shows segmentation characteristics. The noncoaxiality will be overestimated if the elastic strain is considered and is negative when the principal stress rotates in the reverse direction. Reversal of the principal stress leads to abrupt changes in noncoaxiality. However, the noncoaxiality is similar in the process of forward rotation and reverse rotation of the principal stress. With the same cycle period, the noncoaxiality angle decreases with an increase in intermediate principal stress coefficient, but the effect of intermediate principal stress coefficient decreases with an increase in the cycle period. Increases in the cycle period increase the noncoaxiality of the remolded loess, while the influence of the rotation range of the principal stress on the noncoaxiality is not significant.