Search Results (3)

Sand barriers are one of the essential measures used to prevent wind and sand disasters on expressways in desert areas. The article uses Fluent numerical simulation to consider different heights, as well as different spacing from two perspectives, and determine the ideal vertical height of sand barriers (porosity is fixed at 20%). Adding to existing wind and sand flow field research, our analysis of the wind speed and sand characteristics reveals the changing rules that affect a single group of high vertical sand barriers along the highway when considering different parameters and measuring the wind and sand performance. At the same time, we also use field research to verify the accuracy of numerical simulation. The study shows the following. (1) When the airflow passes through the single group of vertical sand barriers, it will form a deceleration zone, acceleration zone, turbulence zone and stabilization zone in different areas, and the overall distribution of the wind and sand flow field is in the shape of a “W”. (2) When the spacing is 4 H, the maximal wind speed in the transition area of the sand barriers is two to three times bigger than that when the spacing is 2 H, which is not conducive to the accumulation of sand particles. When the spacing is 1 H, the maximum wind speed of the two rows of sand barriers is two to three times bigger than that when the spacing is 2, and the two rows of sand barriers overlap in wind protection performance, reducing the overall protective capacity of the sand barriers. (3) As the height of the sand barriers continues to grow, the protective performance of the sand barriers is also enhanced. In the same position around the sand barriers, the wind speed under the 2.5 m sand barriers is lower than that under the 1.0 m sand barriers by 2–3 m/s. It is suggested that the height of the sand barriers should be controlled at 1.5–2.0 m in the actual deployment, and 2 H spacing should be used. Full article

After the construction of desert highway, the physiognomy changes caused by surface wind erosion and accumulation not only seriously threaten the stability of road structure, but also have a tremendous impact on the safety of the highway operation and the maintenance work on the highway. The purpose of this paper is to explore the change of sand sedimentation and the law of sand transport along the highway in the moving dune areas, and to clarify the change of sand flow and the formation mechanism of sand damage in the moving dune areas. Taking the test section of Wuhai-Maqin Expressway in the hinterland of Tengger Desert as the research object, the on-site observation of sand accumulation and the recording of wind information by small weather stations were adopted, supplemented by CFD numerical simulation method, in order to provide reference for the construction of sand control system in moving dune areas. The study results show that: (1) Dunes not only obstruct wind-drift sand but are also the sediment source condition for forming road sand. The windward dunes near the road are affected by wind and the deposition of sand will quickly bury the road in the strong wind season. (2) Compared with highways with flat terrain, the existence of dunes affects the flow field structure and the distribution of sand sedimentation on the highway, in which, under the influence of the gathering effect, the flow velocity reaches the maximum at the top of the dune and a large low-speed recirculation zone is formed on the lee side of the dune, easily causing sand accumulation. (3) Sediment accumulates at the windward side of the embankment or dune where sandy air current is easy to saturate. However, with the increase of wind speed, in addition to the grit carried by the sandy air current itself, new sand rolled up on the windward side of the dunes also form deposits on the road surface and the amount of sand-accumulation on highway surface and leeward side tends to increase. As a result, for the highway in drifting sand dunes areas, sediment prevention and control measures should be taken actively. It is necessary to remove sediment from the road in time and reduce the moving speed of sand dunes and the deposition range of wind-sand flow, ultimately for the purpose of reducing the damage wind-sand activity causes to the highway in desert. Full article

Transportation infrastructure dramatically affects ecological processes. However, the environmental assessment process does not often consider how transportation impacts biodiversity, especially in ecologically fragile areas. The aim of this study was to assess the impacts of the Yulin–Jingbian expressway on vegetative diversity and to discuss the reason for the differences in soil-moisture distribution and vegetation diversity along the expressway. Samples were collected from 60 quadrats, along 6 transects. The α diversity indices and soil-moisture content calculated for each layer were used to represent habitat heterogeneity within a quadrat. A total of 49 species representing 39 genera and 16 families were recorded. Perennial herbs (42.9%) and annual herbs (36.7%) were the dominant life form. Species richness, diversity, and evenness indices of the vegetation varied with the distance between sampling points along the expressway. The vegetation with high diversity and evenness were near the expressway and areas with low diversity were farther from the expressway. The soil-moisture content in the 0–20 cm soil layer was a driving factor for the α diversity indices, and soil-moisture content below 20 cm played an inhibitory role on the α diversity indices. The greatest impact of the expressway on vegetation diversity was its effect on surface runoff and the distribution of plant root systems in the top layer of soil. Full article