青藏铁路块碎石护坡路基降温效果分析

Analysis on Cooling Effect of Embankment with Crushed Rock and Gravel Revetment along Qinghai-Tibet Railway

块碎石路基是青藏铁路中常见的主动冷却路基形式。为了验证该工程措施的有效性,有必要对其长期降温效果进行研究。基于青藏铁路北麓河非正线试验段10 a地温监测数据,对比分析了封闭块石护坡、块石护坡加厚、碎石护坡路基对下部多年冻土的降温效果。研究结果表明,在工程活动和气温变化影响下,三种护坡路基的降温过程存在快速降温、稳定降温、降温减弱三个阶段,其中以碎石护坡路基的降温效果表现最佳。从观测期内的路基下部地温变化和热状态来看,三种路基中心下部原多年冻土上限附近降温速率分别为0.39、0.45、0.47℃/10 a。相较于封闭块石护坡路基,块石护坡加厚、碎石护坡路基下部土体地温分布具有较好的对称性。然而,块碎石护坡路基仅在路基下部5.0 m深度范围内存在降温效果,难以保证深层多年冻土的稳定。

Crushed rock and gravel embankmentsare common types of active cooling roadbed in Qinghai-Tibet railway.To verify the effectiveness of the engineering measures,it is necessary to research their long-term cooling effects.Based on the 10-year monitoring data of ground temperature in the Beiluhe experimental sections along the Qinghai-Tibet Railway,a comparison and analysis were made on the cooling effects of different crushed rock structures,including closed-system crushed rock revetment,open-system crushed rock revetment and open-system crushed gravel revetment,on the permafrost below the embankment.The results show that the embankment with the above three types of crushed rock revetments indicates a three-staged cooling process under the effect of engineering actives and warning climate,including rapid cooling,stable cooling and reduced cooling,with the open-system crushed gravel revetment performing the best.In this process,the cooling rates near the original permafrost table are respectively 0.39,0.45,and 0.47℃/10 a,in terms of the permafrost temperature variation and thermal regime.Compared with the closed-system crushed rock revetment,the soil temperature distributions beneath the open-system crushed rock revetment and open-system gravel rubble revetment perform a better symmetry.However,the aforementioned embankments have a cooling effect on underlying soil in the depth range of about 5.0 m,which is difficult to ensure the stability of deep permafrost.