Formation mechanism and suitable controlling pattern of sand hazards at Honglianghe River section of Qinghai-Tibet Railway

The sand hazards at Honglianghe River section of Qinghai-Tibet Railway are serious, and the effect of controlling measures is limited because the disaster-causing mechanism is currently unclear. The source of sandy materials, blown sand power environment, and controlling measures of Honglianghe River section were investigated by using methods such as field observation and analysis and indoor calculation to understand the sand hazard rules of Qinghai-Tibet Railway systematically. The sandy materials discovered are mainly from the sandy hill of the west side of the railway. In addition, the grain composition of sand with particle size in the range of 0.25-0.10 mm is given priority. Yearly sand-moving winds are usually from the N, NNW, and NW directions. The frequencies of these three wind groups accounted for 85.16 % of the yearly total. The most serious sand hazards were located at the NW direction of the railway. The yearly sand drift potential (DP) is 270.57 vector units (VU), the yearly resultant drift potential (RDP) is 247.27 VU, the yearly direction variability index (RDP/DP) is 0.91, and the yearly resultant drift direction is 162.84A degrees. In windy dry season (during the colder half of the year), loose and broken sand materials are blown up by wind, forming wind-sand flow and movement, which are then blocked by the railway subgrade, and accumulate and thus cause disaster. We propose that the sand-controlling pattern of Qinghai-Tibet Railway is dominated by sand blocking and sand fixing, namely sand blocking in the outer fringe and sand fixing in the inner fringe, supplemented by sand transport and sand diversion, combined with vegetation. This pattern can be a significant reference to controlling sand hazards in other similar zones.