Abstract: [Objective] Qinghai Tibet railway is an important link in the development of the western region of China. As a result of the special natural environment, the frequent occurrence of wind sand disaster has become one of the most important factors affecting the safe operation of the railway. In this study, we used the Fluent software to simulate the different types of Qinghai-Tibet railway subgrade with sand barrier layout and analyzed its wind speed flow field and sediment characteristics. Our aim is to provide a theoretical basis for reasonable layout of sand prevention measures to reduce the accumulation of sand in the subgrade and is to ensure the safe operation of the railway.[Method] With the numerical simulation method, three kinds of subgrade(Ordinary subgrade, Ventilated subgrade, Sand-transmitting subgrade) and two sand barriers(Sleeper typed retaining wall, Sand blocking PE nets) combinations were selected to simulate the flow field and sand distribution, for evaluating the sand prevention effect of sand barrier and analyzing the affecting extent of the subgrade by wind erosion.[Result] Simulation result show that the wind speed field of three types of subgrade all had the same functional partition, and the wind speed had little effect on the flow field. On the windward side, the effect of ordinary subgrade on reducing wind speed was the strongest. Sands were easy to accumulate on the slope and the foot of the slope. The wind speed was significantly increased at the top of subgrade which may affect traffic safety. There was a reflow phenomenon at leeward, leading to the accumulation of sands on the leeward slope under gravity. The sand accumulation on the windward slope of common subgrade was serious and buried rail frequent. The ventilated subgrade would be affected by sand sediment, limiting the permafrost protection. The sand-transmitting subgrade prevented sand accumulation on the windward slope and rail. Once the occurrence of sand deposition on the transport pipeline, could be removed by natural wind. It was also easy to clean up and save a lot of manpower and resources. When the sand-break wall laying before the subgrade, the sand-break wall on the wind speed had a strong weakening effect. There was a deceleration zone between the subgrade and the sand-break wall, the wind speed could not reach the sand-driving wind speed. Sands deposited before and after sand-break wall, the amount of sediment accumulation on subgrade slope was greatly reduced.[Conclusion] Three kinds of subgrade in the absence of protective measures, there are different degrees of sand accumulation. The amount of sediment of sand-transmitting subgrade is minimal, and easy to clean up. The sand accumulation of Sleeper typed retaining wall on the wind side is greater than the leeward side. The sand accumulation of Sand blocking PE nets on the leeward side is greater than the wind. The spacing of sand barrier affects the effect of sand blocking. Appropriate adjusting sand barrier spacing to improve sand blocking effect. According to the simulation, the sand-transmitting subgrade is more suitable for the sandy area. However, the result are still in the theoretical stage and need to be further tested in Plateau environment.

Key words: Qinghai-Tibet railway, wind-blown sand flow, Fluent software, numerical simulation, subgrade