Security Of Heat-insulating Board On Unballasted Track Under The Effect Of Train-induced Air Flow In High Speed Railway

The deformation of unballasted track subgrade is highly restricted.The settlement is restricted whin 15mm,the uplifts is restricted whin 5mm.the frost heave and thawing settlement ofen appears in cold regions.It is an important way to prevent the freeze-thaw deformation of existing lines by laying insulating board on the surface of unballasted track.And one of the key problem in the application of this measure is the safety of the unballasted track insulating board under the negative pressure caused by the train wind.The research of this article is based on this background.Numerical simulation based on FLUENT and wind tunnel test are carried out to analyse the velocity and wind pressure fields on the surface of different types of heat-insulating board.And further study are taken on the safety of the insulation board.The conclusions are presented as follows:?1?The location of maximum negative pressure on the heat-insulating board is between the locomotive and the first bogie as the train passes.The wind pressure on the heat-insulating board is symmetrical along the transverse section of the track,and the maximum negative pressure appears on the center of the track.?2?The maximum negative pressure on the heat-insulating board is also appears between the locomotive and the first bogie when the train passes at the condition of crosswind.The effect of crosswind will increase the negative pressure on the heat-insulating board.?3?The increase of thickness will increase the negative pressure of the board.But the increase in pressure is less than the increase in self-weight.The minimum safe density of the board which is 5cm thick is 4 g·cm^-3.The minimum safe density of the board which is 10cm thick is 2.5 g·cm^-3.The minimum safe density of the board which is 15cm thick is 1.87 g·cm^-3.Therefore,the security of the board which is 15 cm thick is the best at the same train speed condition.?4?Under the condition of same average wind speed.The negative pressure under the load of pulsating wind is larger than the load of mean wind.The negative pressure on the rough surface heat-insulating board is lower than the smooth surface heat-insulating board.