大风区铁路沿线挡风墙积沙机理及优化措施的风洞实验研究

位于兰州至新疆的兰新二线是世界上首条穿越大风区的高速铁路,途径著名的烟墩风区、百里风区、三十里风区及达坂城风区,风区段铁路里程长达 462.4 km,占新疆段线路总长的 65.1${\%}$,大风对铁路的运营、养护和运输造成很大危害. 为了降低大风对通行列车的危害,兰新铁路沿线设置了大量挡风墙. 挡风墙发挥作用的同时,也带来了铁路沿线的积沙问题. 为了解决这一工程实践的现实问题,本文提出了在现有挡风墙背风侧的不同位置处,设立第二道挡墙以减弱铁路积沙的治理思路,并开展了对应条件下对现有单道挡风墙、以及在现有单道挡风墙背风侧坡顶处和坡脚处设置第二道挡墙,共计3种情景的风洞模拟实验,发现设置第二道挡墙后距轨道线路高0.1 m处的沙粒水平速度、数密度、输沙通量及沉积率较无第二道挡墙时明显减少,介于8%$\sim$12${\%}$,51%$\sim$69${\%}$,20%$\sim$73${\%}$以及26%$\sim $38${\%}$,而且在现有单道挡风墙背风侧坡顶部增设第二道挡风墙的效果更好. 因此,本文的研究成果有助于优化大风区已有铁路沿线、城镇等防沙治沙工程措施. 

WIND-TUNNEL EXPERIMENT ON SAND DEPOSITION MECHANISM AND OPTIMAL MEASURES OF WIND-BREAK WALL ALONG RAILWAY IN STRONG WIND AREA1)

The Lan-Xin Railway II from Lanzhou to Xinjiang is the first high-speed railway which passes through the strong wind zones in the world, and it passes through the famous "Yan Dun", "Hundred Miles", "Thirty Miles" and "Dabancheng" wind zones. The total length of the railway is more than 462.4 kilometers, accounting for 65.1${\%}$ of the total length of railway in Xinjiang. Strong winds can do great harm to the operation, maintenance and transportation of railways. In order to resist the damage of strong wind to train, a large number of wind-break walls were built along the Lan-Xin Railway II. The wind-break wall reduces the strong wind damage, but brings a new disaster caused by sand sedimentation. To solve the problem of this engineering practice, this paper puts forward the idea of setting up the second retaining wall at different positions on the leeward side of existing wind-break wall to reduce sand particles sedimentation. The wind tunnel experiment was employed to simulate the wind-sand flow environment. Three typical configurations are considered: 1) single wind-break wall; 2) two walls and the second one locates at the top of the leeward slope of subgrade; 3) two walls and the second one locates at the foot of the leeward slope of subgrade. The decrease rates of the horizontal velocity, number density, horizontal transport flux and deposition rate of sand particles at the height of 0.1 m after the second wall are respectively 8${\%}$$\sim $12${\%}$, 51${\%}$$\sim $69${\%}$, 20${\%}$$\sim $73${\%}$ and 26${\%}$$\sim $38${\%}$, by comparing to the case without the second wall. It is found that the second retaining wall at the foot of the leeward slope of subgrade is optimal. The research result of this paper is helpful to optimize the preventing sand sedimentation measures of existing railway lines and towns in the strong wind zone.