Abstract: The hollow cylinder apparatus at Tongji University was used to conduct the torsional shear test on the dry TJ-1 lunar soil simulant by applying fixed and rotated principal stress axes. In the perspective of the stress-strain response, the investigation is focused on the effect of the principal stress direction and the deviatoric stress ratio on the anisotropy of the dry TJ-1 lunar soil simulant. In addition, their impact on the non-coaxiality of the specimen is also further explored. The test results indicate that the principal stress direction and the deviatoric stress ratio significantly affect the anisotropic behavior of the TJ-1 lunar soil simulant. The non-coaxiality observed in the torsional test with rotated principal stress direction is more remarkable than that in the tosional test with fixed principal stress direction. In the test with rotated principal stress direction, the non-coaxial angle decreases and then increases at a small deviatoric stress ratio; while the angle continuously decreases at a high eviatoric stress ratio and diminishes as the specimen failure. This study will help to fill the gap in the research with emphasis on anisotropic behaviors of dry sands; and it also provides necessary theory beneficial to the future development of human infrastructure on the Moon.

Key words: TJ-1 lunar soil simulant, principal stress direction, deviatoric stress ratio, anisotropy, non-coaxiality