# Numerical Simulation Research on Plane Alignment Parameters of Desert Highway
## 1 Introduction  
Arid and semi-arid areas account for more than 30% of the global land area, and deserts account for 10.3% of land area [1]. Among them, the desert area in China is about 700,000 km\({}^{2}\), accounting for about 19% of the global desert area, mainly concentrated in the inland basins and plateau areas in the northwest and north of China [2, 3]. To promote the economic development of the northwest region, highway construction has gradually extended to desert areas, but desert highways are easily affected by wind-sand weather. If the selection of plane alignment design parameters is unreasonable, it will further lead to the occurrence of sand damage, such as sand accumulation and wind erosion on the road embankment, which will affect driving safety [4, 5]. For this reason, many researchers have carried out a large number of wind-tunnel tests, numerical simulations, and field data analyses to determine reasonable plane alignment parameters and ensure driving safety. In recent years, scholars [6, 7, 8, 9] have systematically studied the relationship between the curve radius, the driving speed, and the driver's heart-rate change by means of experiments and modeling from the perspective of driving safety. The minimum and recommended values of the road curve radius in the Gobi Desert area have been determined. According to the experience gained from many lines built crossing the desert (Taklimakan Desert highway, Lanzhou-Xinjiang high-speed railway, Iran railway), the influence of wind-sand activity characteristics should be fully considered in the early design stage [10, 11, 12, 13]. At the same time, the data of existing lines where sand damage often occurs should also be analyzed to provide ideas for later designs. [PERSON] and [PERSON] [14] summarized and analyzed theroute selection data of the Baotou-Lanzhou railway and found that the route selection in the desert area should avoid the moving sand dunes as much as possible, and the flat curve is easy to use as the large radius curve. [PERSON] [15] summed up the experience of the route selection of the Korta-Golmud railway and put forward the suggestion that the outer side of the curve should face the main wind direction of the selected route in the sandstorm area. [PERSON] [16] put forward the plan to lead the road with bridges through the floating sand dune area in a section of the Hotan-Ruoqiang railway line. Although the above scholars have elaborated on the basic principles of railway-line selection in the Gobi Desert area, the mechanisms of action need further study. Computational fluid dynamics (CFD) have been widely used in the fields of bridges [17], railways [18], and construction engineering [19], and it has become an important way for researchers to study wind-blown sand movement [20; 21; 22; 23]. Therefore, scholars [24; 25] used numerical simulation to study the interaction mechanism between wind-sand flow and embankments. In 2008, [PERSON] [26] used the Fluent-Euler two-fluid model to describe the mechanism of action between wind-sand flow and embankments and optimized the parameters of the embankment under the action of wind-sand flow. [PERSON] [27] used wind-tunnel experiments and numerical simulation to study the flow-field-distribution characteristics of embankments and cuttings under the action of wind-sand flow. [PERSON] [28] used the Euler two-fluid model to analyze the flow-field changes and sand accumulation characteristics when wind-sand flows through the embankment. At present, the research on the response law of wind-sand flow and embankments is mainly based on wind-tunnel experiments and numerical simulation, and the analysis is mainly carried out from a two-dimensional perspective, but the three-dimensional numerical simulation of sand flow combined with a flat-curve embankment is rarely involved. The paper relies on the Tengger Desert section of the Wuhai-Maqin Highway, and is based on the CFD software, as well as the angle between the wind direction and the line direction.