基于高原隆升裂点理论的中尼铁路泥石流特征及减灾选线要点

Characteristics of Debris Flow and Key Points of Disaster Reduction and Route Selection of China-Nepal Railway Based on Plateau Uplift Knickpoint Theory

拟建中尼铁路始于我国西藏日喀则市,途经雅江、朋曲、吉隆3个流域到达尼泊尔加德满都,长约600 km,其中约2/3长度的线路位于雅江、朋曲两个流域,泥石流沟数量较多,是对线路方案具有控制性作用的灾害类型。首先,基于青藏高原隆升的河流裂点理论,判定中尼铁路行经的雅江流域段已处于前期地貌回春阶段,朋曲河段仍处于老年期地貌阶段。然后,基于朋曲流域夷平面占比远大于雅江的现象,分析得到夷平面的存在将影响地表汇流时间以及使泥石流流域连通性下降等规律,据此提出雅江流域泥石流运动条件优于朋曲的推论。最后,结合雅江流域铁路行经河流,河床将持续上涨、朋曲流域山前存在广阔的洪积砾石斜缓地带的特点,提出雅江流域需整体提高线路设计高程、朋曲流域宜采取同岸外移绕避的减灾选线要点。研究成果可为中尼铁路线路方案优化提供科学依据,有关将高原隆升的宏观理论推进到工程应用层面的工作可望产生范例性作用。

The proposed China-Nepal Railway starts in Shigatse City,Tibet,China,and reaches Kathmandu,Nepal,through the Yaluzangbu River,Pengqu River and Gyirong Basins.It is about 600 km.About 2/3 of the length of the line is located in the Yaluzangbu River and Pengqu River Basins.The large number of debris flow gullies is a disaster type that has a controlling effect on the route scheme.Firstly,based on the river knickpoint theory of the uplift of the Qinghai-Tibet Plateau,it is determined that the Yaluzangbu River section of the China-Nepal Railway is in the early stage of geomorphic rejuvenation,and the Pengqu River section is still in the old-age geomorphic stage.Based on the phenomenon that the proportion of planation surface in the Pengqu River Basin is much larger than that in the Yaluzangbu River Basin,it is analyzed that the existence of planation surface will affect the time of surface confluence and reduce the connectivity of debris flow basin.Based on this,it is concluded that the movement conditions of debris flow in the Yaluzangbu River Basin are better than those in the Pengqu River Basin.Finally,combined with the characteristics that the riverbed of the Yaluzangbu River Basin railway will continue to rise,and there is a broad sloping zone of diluvial gravel in the piedmont of the Pengqu River Basin,it is proposed the key points of disaster-reduction route selection that the Yaluzangbu River Basin needs to improve the design elevation of the line as a whole,and the Pengqu River Basin should adopt route selection to avoid the same bank.The research of this paper can provide scientific basis for the optimization of China-Nepal railway line scheme,and the work of promoting the macroscopic theory of plateau uplift to the level of engineering application is expected to produce exemplary effect.