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The interface between soil and concrete in cold climates has a significant effect on the structural integrity of embedded structures, including piles, liners, and others. In this study, a novel temperature control system was employed to conduct direct shear tests on this interface. The test conditions included normal stress (25 to 100 kPa), temperature (ranging from 20 to −6 °C), water content (from 10 to 19%), and shear rates (0.1 to 1.2 mm/min). Simultaneously, the deformation process of the interface was continuously photographed using a modified visual shear box, and the non-uniform deformation mechanism of the interface was analyzed by combining digital image correlation (DIC) technology with the photographic data. The findings revealed that the shear stress–shear displacement curves did not exhibit a discernible peak strength at elevated temperatures, indicating deformation behavior characterized by strain hardening. In the frozen state, however, the deformation softened, and the interfacial ice bonding strength exhibited a positive correlation with decreasing temperature. When the initial water content was 16% and the normal stress was 100 kPa, the peak shear strength increased significantly from 99.9 kPa to 182.9 kPa as the test temperature dropped from 20 °C to −6 °C. Both shear rate and temperature were found to have a marked effect on the peak shear strength, with interface cohesion being the principal factor contributing to this phenomenon. At a shear rate of 0.1 mm/min, the curve showed hardening characteristics, but at other shear rates, the curves exhibited strain-softening behavior, with the softening becoming more pronounced as shear rates increased and temperatures decreased. Due to the refreezing of interfacial ice, the residual shear strength increased in proportion to the reduction in shear rate. On a mesoscopic level, it was evident that the displacement of soil particles near the interface exhibited more pronounced changes. At lower shear rates, the phenomenon of interfacial refreezing became apparent, as evidenced by the periodic changes in interfacial granular displacement at the interface. [ABSTRACT FROM AUTHOR]

To investigate more fully seismic behaviour of the Qinghai-Tibet railway embankment, a comprehensive discussion and a781nalysis is conducted in this paper by applying a numerical technique. Specifically, the one dimensional equivalent linear ground response analysis was conducted in permafrost regions. On this basis, the seismic response of a typical railway embankment was further studied by applying the nonlinear dynamic finite element analysis method. As a result, nonlinear behaviour of permafrost sites was determined, and the dynamic acceleration, velocity and displacement of the embankment was discussed and the quantitative assessment was approximately estimated. The results indicate that the dynamic response of the embankment has distinct nonlinear characteristics. The peak ground acceleration coefficient at the embankment shoulder is larger than the natural ground surface, marking a 73% increase compared to the coefficient on the natural ground surface. When the seismic intensity reaches a certain value, a plastic zone gradually appears in the embankment, and a continuous extension of the plastic zone can be noted with an increase in peak acceleration of the input seismic wave. The findings of this research may provide an additional insight and have significant implications for further research of cold regions.

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 °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. [ABSTRACT FROM AUTHOR]

The interfacial frictional resistance of anchor solids, bolt, and the surrounding soil of soil nails in the flexible support structures of frozen soil slopes is a key parameter for calculating and evaluating its stability. Based on a series of direct shear tests under the condition of a constant normal load boundary, the shear mechanical behavior of the interface between the soil and a cement slurry block under different soil temperatures, water contents, and normal pressures was studied, and the interfacial deformation mechanism was analyzed. The results show that in the thawing state, with the increase of water content, the shear surface moves from the side close to the soil to the side close to the cement slurry block. However, the shear plane is determined in the direct shear test, which makes the effect of the change of the soil's own strength on the interfacial shear strength smaller. In the frozen state, the behavior of the interfacial shear stress–shear displacement behavior at the same water content varies from strain-hardening type to strain-softening type with the temperature decreasing. The normal displacement is affected by temperature, normal pressure, and water content. At the same temperature, the maximum normal displacement gradually decreases with the increase of water content and normal pressure. At the same normal pressure and water content, the maximum normal displacement tends to increase and then decrease as the temperature drops. Still, the maximum normal displacement in the frozen state is more significant than in the thawing state. At the same water content and normal pressure, the interfacial peak shear strength shows a nonlinear increase with the decrease in temperature. At the same normal pressure and temperature, the interfacial peak shear strength delivers a linear increasing law with increasing water content. The peak interfacial cohesion increases with the decreasing temperature and increasing water content, and this phenomenon is more evident at lower temperatures. The interfacial friction angle does not change significantly with the rise in water content at the same temperature, but as temperature decreases, its average value increases significantly. The research results can provide a reference for the design of slope support structures in cold regions. [ABSTRACT FROM AUTHOR]