Study on the Characteristics of Flow Field and the Mechanism of Wind-blown Sand Disasters in the Tuotuohe Region along the Qinghai-Tibet Railway

Abstract

Qinghai-Tibet Railway,with an average altitude of 4 500 m a.s.l.,is the longest railway in the high-altitude region in the world.It passes through 550 km-long permafrost belt and crosses the Kunlun Mountains and Tanggulha Mountains on the Qinghai-Tibetan Plateau.Based on the wind tunnel experiment of flow filed structure and wind profiles around the railway bed along the Tuotuohe section of the Qinghai-Tibet Railway,it is considered that a section of railway bed will obviously change the pattern of flow field near ground surface,and there are the obvious blocked-rising area,collected-accelerating area,decreased-depositing area and diffused-restoring area of airflow in a flow field.The mechanism of wind-blown sand disaster formation along the railway is mainly as follows: wind erosion occurs at the railway shoulder or the mid-upper part of railway bed because airflow at windward slope is forced to lift and accelerate;sand grains in the bottom layer deposit at the toe of windward section and bury the railway bed as airflow is enforced to lift;wind-blown sand is in a supersaturation state and accumulates at leeward slope of the railway bed because of the wind speed decrease and eddy motion when airflow gets across the railway bed.The Qinghai-Tibet Railway is destined to suffer from wind-blown sand disasters.With climate change and increase of human activities,the occurring frequency of wind-blown sand disasters along the railway will increase in the future.In a word,it has become a new challenge for both government and scientists how to control wind-blown sand disasters along the Qinghai-Tibet Railway in an effective and scientific way.