戈壁特大风区风沙危害的动力学机制及防治研究——以兰新高铁为例

The Lanzhou-Xinjiang High-speed Railway (LXHR) runs through four strong wind areas where land surfaces are all featured by Gobi. The threat from blown sand/gravel by extra-large wind in these areas endangers the operation of the railway. However, researches on Gobi, particularly the Gobi wind-blown sand physics under extra-large wind condition, is still limit and the current blown-sand control system failed to ensure the safety of running trains during strong windy days. This project aims to research the initiation, release, and transportation processes and mechanisms of blown-sand and gravel, as well as their interaction with blown-sand control engineering, and then to establish the technologies to control blown-sand and gravel in the extremely windy region using synthetical field observation, wind tunnel experiment, and numerical simulation methods. This work will enrich the studies on wind-blown sand physics and related engineering science, and connect the research and application works in Gobi area with large winds. This is also the first study on the wind-blown sand control engineering of high-speed railway in strong wind area. The result will provide guidance to release the blown-sand related problems for the railways, highways, and cities in the countries along the “One Belt and One Road”.

兰（州）—新（疆）高速铁路途径四大风区，地表以戈壁为主，特大风驱动下的风沙/砾流灾害是其安全运营所面临的首要问题，也是风沙物理学悬而未决的科学问题。由于特大风条件下的戈壁风沙/砾过程研究不足，兰新高速铁路既有防沙工程难以确保列车在特大风沙天气下安全运营。本项目拟通过野外监测、高速风洞模拟实验和数值模拟等手段，深入系统研究特大风条件下风沙/砾起动、释放和传输过程和机理，防沙工程与风沙/砾流相互作用过程，提出适合特大风区风沙/砾防治关键技术和途径。这不仅具有丰富风沙物理与工程学研究内容，弥补特大风条件下戈壁风沙理论研究的不足与应用的脱节，填补特大风区高速铁路风沙工程学研究的空白等重要的科学意义。而且，对于“一带一路”沿线国家铁路、公路和城镇风沙危害防治都具有重要的借鉴意义。

兰新高铁途径四大风区，地表以戈壁为主，特大风驱动下的风沙/砾流灾害是其安全运营所面临的首要问题，也是风沙物理学悬而未决的科学问题。由于特大风条件下的戈壁风沙/砾过程研究不足，兰新高速铁路既有防沙工程难以确保列车在特大风沙天气下安全运营。本项目通过野外监测、高速风洞模拟实验和数值模拟等手段，深入系统研究了特大风条件下风沙/砾起动、释放和传输过程和机理，防沙工程与风沙/砾流相互作用过程，提出了适合特大风区风沙/砾防治的关键技术和途径。得到以下结论：①翻越天山的北方冷空气经垭口、沟谷、洪积扇等复杂地形时，受“狭管效应”及“下坡效应”作用，气流加速、风力增大2~3倍，是造成铁路沿线大风频发、沙害严重的重要原因。②戈壁特大风地区输沙高度达9m，远大于一般沙漠、戈壁地表，输沙率随高度的增加指数递减。沙粒跃移高度受风速和颗粒粒径共同控制，大风作用下的粗颗粒与戈壁面碰撞具有更强的动能，戈壁风沙/砾流动能通量密度随高度变化遵循Pearson VII曲线，在近地表0.09-0.15 m高度范围内存在动能最大值。③砾石覆盖度是戈壁地表沙/砾起动的主要影响因子,当砾石覆盖度为10-50%时，起沙风速随砾石覆盖度增加呈直线增大，而当砾石盖度大于50%时，起沙风速受砾石覆盖度的影响程度显著降低。砾石起动风速受砾石粒径和沙源供给度的共同影响,砾石起动风速随砾石粒径增加呈对数规律增大，当达到一定沙源供给度时，起动风速随砾石粒径的增加其增幅变缓。④不同含沙量与砾石覆盖度戈壁输沙率差别巨大，烟墩风区沙砾质戈壁输沙率Q与u(u2-ut2)成正比，南湖沙质戈壁Q与u*(u*2-u*t2)呈幂函数关系，比例系数高达2.5。⑤筛选和研发了适宜于戈壁特大风区的防沙新材料，提出了“以阻为主，阻固结合”的戈壁特大风区风沙防治理念，构建了“多排前沿阻沙带加高立式大网格固沙带”的戈壁特大风区综合工程防沙体系，体系下风向输沙量降低87.87%。本研究弥补了特大风条件下戈壁风沙理论研究的不足，加强了特大风区高速铁路风沙工程学研究。