Dynamic behaviors of frozen silt under repeated traffic loading

The temperature state of warm permafrost is in the negative temperature near-phase-transition interval and thus is extremely sensitive to small fluctuations of the heat and stress environment. The dynamic load induced by the vehicle operation not only changes its magnitude cyclically, but also its principal stress direction (PSD) consistently changes rotationally. However, the existing conventional dynamic research methods can only simulate the cyclic stress environment with constant PSD, which is very different from the stress environment induced by locomotive operation, and thus the conventional dynamic research results are bound to be difficult to accurately reflect the influence of the stress field induced by vehicle operation on the development law of warm permafrost permanent settlement deformation. Therefore, in this paper, a series of dynamic studies were carried out for the Qinghai-Tibet silt at -2 degrees C by simulating the cardioid-shaped stress path induced during the operation of a heavy-duty locomotive using a frozen hollow cylinder apparatus. It is found that the rotational effect of the principal stress direction under the conditions of the cardioid-shaped stress path (CSSP) action accelerates the development of vertical permanent deformation in the frozen soil. The main reason that caused the axial strain increases advantage is the rotation of principal stress direction can accelerate the viscous energy dissipation during dynamic loading process. According to the law of axial strain development in the high-temperature frozen soil under the conditions of different CSSP action, an empirical model of permanent deformation development in high-temperature frozen soil considering the PSD rotation effect was established, and it was found by this model calculation that under the general condition of heavy-load locomotive operation, compared with the conventional research method without considering the PSD rotation, the axial cumulated strain in high-temperature frozen soil increased by 33.3% after considering the rotation effect in the PSD.