The Qinghai-Tibet Expressway is a major strategic project planned by China that will be built along the Qinghai-Tibet Engineering Corridor.At present,important traffic line projects,such as the Qinghai-Tibet Railway,have been built within this narrow corridor,particularly at the blown sand sections.How to ensure that the wind speed and its flow field between the new expressway and existing railway subgrades are not affected by each other is a priority to prevent breaking the dynamic balance of the blown sand movement of the existing subgrade,thereby avoiding aggravating or inducing new blown sand hazards and ensure the safe operation of the existing Qinghai-Tibet Railway.Therefore,defining the minimum distance of the wind speed and its flow field,which are not affected by each other,between the subgrades become a scientific problem that should be solved immediately to implement the construction of the Qinghai-Tibet Expressway.For this purpose,the minimum safe distance between the subgrades of the Qinghai-Tibet Expressway and Qinghai-Tibet Railway was investigated from the perspective of blown sand by making subgrade models for conducting wind tunnel experiments and combining the observation data of the local field.Results indicated that the minimum safe distance between the two subgrades is 45-50 times the subgrade height when the Qinghai-Tibet Expressway is located at the downwind direction of the Qinghai-Tibet Railway,and 50 times the subgrade height when the former is located at the upwind direction of the latter.These results have guiding significance for the route selection,survey,and design of the Qinghai-Tibet Expressway at the blown sand sections and for the traffic line projects in other similar sandy regions.