青藏铁路多年冻土区片石护坡积沙段降温效果监测与分析

青藏铁路多年冻土区的片石护坡路基的大量使用,起到了降低路基基底多年冻土温度和调节多年冻土人为上限形态的作用,为青藏铁路的安全运营提供技术保障。青藏铁路多年冻土区沿线沙害主要分布在线路经过的河谷及湖泊附近,在风沙危害严重地段,片石护坡孔隙被沙害掩埋,改变了片石层传热特性,影响片石护坡的降温效果。通过室内试验及现场地温监测分析,根据不同条件(有无积沙、阴阳坡)对片石护坡的降温效果进行了对比分析,研究结果表明:(1)由于片块石层的大孔隙特性,使得片块石护坡能通过暖季隔热、寒季散热这一机理来对路基体进行降温,测温数据显示降温效果良好;(2)片石护坡积沙后其降温效果明显减弱,通过片石层内0.6 m和0.8 m深度的地温积温比较,积沙路段积温明显高于无积沙路段,其中路基阳坡侧高出约50%,路基阴坡侧高出约100%。

Monitoring and Analysis of Cooling Effect of Sand Hazard Riprap Slope Protection in Permafrost Regions along Qinghai-Tibet Railway

The extensive use of riprap slope protection subgrade in permafrost area of Qinghai-Tibet Railway has played a role in lowering permafrost temperature of subgrade and adjusting artificial upper limit form of permafrost, which provides technical guarantee for the safe operation of Qinghai-Tibet Railway. Sand hazards along the permafrost area of Qinghai-Tibet Railway are mainly distributed in the valleys and lakes where the road passes. In areas with severe wind and sand hazards, the pore of riprap slope protection is buried in sand, which changes the heat transfer characteristics of riprap slope layer and affects the cooling effect of riprap slope protection. Based on indoor test and on-site monitoring and analysis of ground temperature, the cooling effect of riprap slope protection is compared and analyzed according to different conditions(with or without sand accumulation and shady side-sunny side). The results show that:(1) Because of the macro porous characteristics of the debris layer, the riprap slope protection can cool the roadbed through the mechanism of heat insulation in warm season and heat dissipation in cold season. The mechanism of heat insulation in warm season and heat dissipation in cold season can be used to cool the roadbed. The temperature measurement data show that the cooling effect is good.(2) The cooling effect of the gravel slope protection is obviously weakened after sand accumulation. The comparison between the accumulated temperature at 0.6 m and that at 0.8 m in gravel layer indicates that the accumulated temperature of gravel road section is obviously higher than that of non-gravel road section, where the accumulated temperature of the sunny side of subgrade is about 50% higher and that of the shady side of subgrade is about 100%.