Analysis Of Sand Hazard Character And Sand Transport Path In Beilu River Section Along Qinghai-Tibet Railway

Qinghai-Tibet Railway has been suffering from sand hazard since its opening.With the deployment of sand control measures,along the overall sand damage situation has been eased,however,some sections of the sand is increasingly serious.The unique geographical location of the Qinghai-Tibet Railway makes its sand damage characteristics different from other railway cranes.It is necessary to systematically study the sand damage characteristics of the QinghaiTibet Railway in order to formulate the appropriate anti-sand measures for the alpine railway against the sand barrier characteristics of the Qinghai-Tibet Railway.We selected Beilu Revier section of the Qinghai-Tibet Railway as a research area.On the basis of the on-site investigation,the sand damage of the Beilu River is systematically analyzed with the indoor experiment and related data:(1)By analyzing the trend of climate change and the characteristics of local wind conditions,in order to obtain the characteristics of the driving force of sand barrier in Beilu River section;(2)Through the investigation and analysis of the vegetation and soil in the experimental area,the soil and vegetation characteristics of the sandy dust source were obtained,and the characteristics of the sandy soil were analyzed;(3)By analyzing physical and chemical properties of soil,and terrain,wind erosion as well as wind volume experiment of sand material,we predicted the transport path of sand material;(4)According to the improved method of calculating the amount of accumulated sediment in the field,the amount of sediment accumulated in the Beilu River and Nanshankou was calculated to evaluate the protective effect of sand control measures.The main conclusions as follows:(1)Climate change indirectly affect the sand damage,wind changes directly affect the occurrence and development of sand damage,The precipitation and temperature of the Beilu River area have a tendency to increase,and in recent years is still in the period of increasing,the climate has damp heat of the development trend;The dominant winds in the area are W and WNW,the larger wind time is mainly concentrated in 11-12 months(winter),1-3 month(spring),The area is a high-energy environment,but the wind energy environment is declining for many years.After 2007,the wind speed slows down and stabilizes.The direct driving force tends to be stable and the increase of indirect trend will also promote the occurrence of sand damage.Therefore,this study suggests that the driving force of sand damage in Beilu River section is increasing and the sand damage situation will be enhanced.(2)Based on the investigation of the vegetation in the experimental area,59 species and 36 genera of 19 families and 36 genera of the herbaceous plants were obtained.The main dominant species are Carex moorcroftii,Kobresia pygmaea,Androsace tangulashanensis,and Leontopodium pusillum.Through the investigation of the sand in the sand barrier area,it is found that the sand size range of the sandy section of the northern foot is 63-500?m.According to the degree of wind erosion,it was found that the contents of 63-500?m were more than 55%,which indicated that the potential wind erosion potential of each type of dust source was relatively high,In the event of sand and dust weather,the area with more sediment concentration is mainly concentrated in the Bei Lu River and Xiushui River and nearby areas.The vegetation richness is between 9 and 11,and the vegetation coverage is between 9.86 and 24.60%.The dominant species are Carex moorcroftii,Androsace tangulashanensis and Stipa glareosa.The vegetation richness is between 7.57-8.50 and the vegetation coverage is between 24.60 and 30.30%.The dominant species are Androsace tangulashanensis,Carex moorcroftii and Kobresia pygmaea.The vegetation coverage was between 12.90 and 26.80%,and the dominant species were mainly Carex moorcroftii,Kobresia pygmaea,and Leontopodium pusillum.The vegetation coverage with strong resistance to wind erosion was between 12.10 and 16.61%,and the dominant species were Carex moorcroftii,Androsace tangulashanensis.(3)The study of sand transport path in the Beilu River area is divided into two parts: hydraulic sediment transport and wind transport.The hydraulic sedimentation occurred in the rainy season of the Beilu River(May-September).The wind transport occurred in the wind season(11-4 months),The channel formed by hydraulic erosion and the channel of the Beilu River and Xiushui River,mainly distributed on the slopes of the south side of the Beilu River.The main source of wind transport is the main conveying direction of the main wind direction,and the sediment transport volume is the largest,then the amount of sediment transport is larger between the Beilu River and the Xiushui River,the south side of Beilu River has the minimum amount of sediment,but the opposite process in sand deposited.(4)At the time of investigation,the first two sand dunes of the Beilu River reach 20 m3/m,and the total amount of accumulated sediment in the sand barrier area of Nanshankou is 6.75m3/m.The severity of sand damage in Beilu River section is much greater than that in Nanshankou section.The accumulation of sand barrier in the Beilu River shows the law of the farther away from the river.In the sand control measures,the PE grid sand barrier has better sand control effect than the stone grid sand barrier.There are few differences in the degree of sand damage between the north and south sides of the Beilu River section.The number of rows of sand barrier in the south bank should be reduced and the number of sand barrier in the north bank should be increased.Beiliu River sand control measures mainly to block sand.It is suggested that the sand control measures on both sides of the river should be based on the east and the west of Beilu River to reduce the sand accumulation pressure on the sand barrier.