Study on the Effect of Unilateral Sand Deposition on the Spatial Distribution and Temporal Evolution Pattern of Temperature beneath the Embankment

In the context of climate warming and the frequent wind-sand hazards in the Qinghai-Tibet Engineering Corridor (QTEC), the construction of the embankment will affect the thermal regime of permafrost underground. The influence of embankment construction on the variation of the permafrost table beneath it is different, especially for the regime with different mean annual ground temperatures (MAGTs). In this study, the effects of the unilateral sand particles deposition on the spatial distribution and temporal evolution pattern of temperature beneath the embankment are investigated through the numerical simulations, in which the heat transfer is considered. The model is validated by the field observed data of soil temperatures around an experimental zone built at the sand hazard area in Honglianghe, the interior of Qinghai-Tibet Plateau (QTP). The simulated results indicate that the temperature field beneath the embankment is asymmetrically distributed under the condition of unilateral sand particles deposition. This asymmetry gradually weakened with the increase of operation time and the gradual adjustment of the permafrost temperature field. By comparing the permafrost table beneath the natural surface, the sand deposition center, and the middle of the embankment center, it could be found that the unilateral sand particles deposition has less effect on the degradation of the permafrost table in the center of the embankment. However, for the center of the sand deposition, the change of the permafrost table is larger with the increase of time and the corresponding rate of permafrost table degradation is higher than that without sand particles deposition, especially for the high-temperature permafrost. In addition, with different sand thickness and width conditions, the effect of "narrow-thick" form sand particles deposition on the temperature field beneath embankment is greater than that of "wide-thin" form sand deposition. Hence, in order to reduce its impact on the long-term thermal condition beneath the embankment, it is necessary to clean the thicker deposition sand particles at the toe of the embankment.