风沙堆积对下伏多年冻土影响的数值模拟

青藏高原沙漠化所产生的风沙堆积作为一种重要局地因素，其对下伏多年冻土的具体影响目前尚未清楚。通过数值方式，模拟了红梁河沙害严重地区高温退化型多年冻土在13种厚度的干湿风积沙覆盖下10年内的变化情况。结果表明：在土体浅层，沙层越厚，地温较差越小，且干沙下地温较差变化幅度明显大于湿沙；干沙越厚，最大季节融深越小，湿沙则对最大季节融深影响微弱；积沙无论干湿，沙层越厚，冷暖季年热循环量均越小，且干沙下年热循环量变化幅度明显大于湿沙。因此，风积沙对其下伏多年冻土退化有不同程度减缓，沙层越厚，减缓作用越强，且干沙减缓多年冻土退化的能力明显强于湿沙。

Numerical simulation of the effect of aeolian sand accumulation on permafrost

Aeolian sand accumulation caused by desertification is a significant local factor for permafrost in the Tibetan Plateau. However, the mechanisms about the effect of the aeolian sand on permafrost are still unclear. In this study, based on the soil phase change heat transfer theory and Comsol Multiphysic software, the states of soil temperature and the active layer depth of warm degenerate permafrost under 13 dry and moist sand covers are simulated for 10 years in the sand hazard area in Honglianghe. The results show that the shallow permafrost temperature range and the maximum seasonal thawing depth, as well as the heat cycle in cold and warm seasons, decrease with the sand cover thickness. In addition, the decreasing amplitude of permafrost temperature, active layer depth and heat cycle with dry sand cover are larger than that with moist sand cover. Therefore, aeolian sand accumulation can slow down the permafrost degradation in different levels in the research area. The thicker the sand cover is, the stronger the slowing effect is. Furthermore, the slowing effect of dry sand cover is stronger than that of moist sand cover obviously.