风积沙对青藏铁路块碎石路基降温效果的影响

风沙危害正在威胁着青藏铁路的安全营运. 通过数值方法研究了风积沙填堵和覆盖青藏铁路块碎石路基后, 块碎石层降温机理以及降温效果的变化特征. 结果表明:开放条件下块石路基具有较强的强迫对流效应; 风积沙填堵后, 块碎石层降温效果减弱. 封闭条件下, 冷季路基坡脚处自然对流较强, 冻土上限抬升; 路基内部自然对流较弱, 由于路基填土作用, 路基中心处冻土上限抬升较大, 但随时间增长而降低; 沙层覆盖后, 块碎石层降温效果减弱, 路基下部冻土上限下降. 在气候变暖背景条件下, 封闭块碎石层自然对流减弱, 冻土上限下降, 不利于冻土路基的热稳定. 因此, 建议对沙害路段的块碎石路基采取补强措施.

Impacts of aeolian sand on cooling effect of crushed-rock embankment of Qinghai-Tibet Railway

Aeolian sand has damaged the Qinghai-Tibet Railway. In this study, the impact of aeolian sand on cooling effect of crushed-rock embankment of Qinghai-Tibet Railway is investigated on the basis of a coupled mathematical model of convective heat transfer and heat conduction with phase change. In addition, climate warming is also considered. The results show that extensive convection can be produced in the layer of block-stone for open block-stone embankment. After the crushed-rock layer filled with aeolian sand, it is clear that the cooling effect of crushed-rock embankment will drop off, which can be seen by analyzing velocity variation in the rock layer, then permafrost table will rise gradually. The cooling mechanisms of the closed embankment significantly depend on natural convection. The artificial permafrost table beneath the center of embankment is higher than that of the adjacent regions due to the impact of filling soil. After the surface of closed rock layer buried by aeolian sand, natural convection intensity weakens gradually. In addition, the cooling effect of rock layer can counteract the negative effect of climate warming and can uplift the permafrost table. The results can provide a guide for the infrastructure design and reinforcing Qinghai-Tibet Railway in permafrost regions.