The influence of cyclic loading on frozen soil may be reflected by the variation of soil temperature. To uncover this process, dynamic triaxial tests were performed in this study on saturated warm frozen soil, during which the temperature changes inside the specimens were monitored. The effects of initial dry density, test temperature, dynamic stress amplitude and vibration frequency on temperature change were studied. The results universally manifested a rise in specimen temperature under cyclic loading. The higher dynamic stress, vibration frequency, testing temperature and initial dry density was responsible for the faster heating rate. The mechanism controlling the temperature variation inside the specimens could be explained by the heat production as a result of friction and extrusion between soil grains when subjected to dynamic loading. This temperature rise could be compromised by the heat transfer with the thermal environment where the specimen was in. A colder environment would cause the specimen temperature to drop back. This study provides an experimental foundation for deeply understanding how the mechanical behavior of frozen soil degrades under dynamic loading.

Affected by climate warming and anthropogenic disturbances, the thermo-mechanical stability of warm and ice-rich frozen ground along the Qinghai-Tibet Railway (QTR) is continuously decreasing, and melting subsidence damage to existing warm frozen soil (WFS) embankments is constantly occurring, thus seriously affecting the stability and safety of the existing WFS embankments. In this study, in order to solve the problems associated with the melting settlement of existing WFS embankments, a novel reinforcement technology for ground improvement, called an inclined soil-cement continuous mixing wall (ISCW), is proposed to reinforce embankments in warm and ice-rich permafrost regions. A numerical simulation of a finite element model was conducted to study the freeze-thaw process and evaluate the stabilization effects of the ISCW on an existing WFS embankment of the QTR. The numerical investigations revealed that the ISCW can efficiently reduce the melt settlement in the existing WFS embankment, as well as increase the bearing capacity of the existing WFS embankment, making it favorable for improving the bearing ability of composite foundations. The present investigation breaks through the traditional ideas of active cooling and passive protection and provides valuable guidelines for the choice of engineering supporting techniques to stabilize existing WFS embankments along the QTR.

This paper presents the establishment of a macro-mesoscopic constitutive model based on poromechanics for investigating the mechanics of warm frozen soil. The elastic parameters of warm frozen soil are influenced by the ice content variations during the loading process, considering the pressure melting characteristic of warm frozen soil. Through the integration of poromechanics and mesomechanics, a macro-mesoscopic constitutive model incorporating the pressure melting effect is developed to characterize the mechanical properties of warm frozen soil. The proposed model establishes a relationship between the elastic modulus at the mesoscopic and macroscopic scales of warm frozen soil.To validate the model, a comparison is made between the model predictions and experimental data obtained from warm frozen silt. The results demonstrate that the model effectively captures significant mechanical performance of warm frozen soil, including strain soft and dilatancy phenomena under various confining pressure conditions. Furthermore, the proposed model enables the prediction of freezing temperature, unfrozen water saturation, unfrozen water pressure, ice pressure, and porosity changes in warm frozen silt samples during the loading process.