Shengbo Xie

The Liuyuan-Golmud Expressway is located in an inland hyper-arid region, where the dominant environmental feature along the route is the Gobi aeolian sand environment. Current understanding of the Gobi surface characteristics, wind dynamic environment, and sand transport regularities along the route remains limited. This has hindered the development of targeted blown sand prevention and control measures and has resulted in severe blown sand hazards on the expressway. Based on Gobi field investigation, sampling, and analysis, the surface sediments of the Gobi along the Liuyuan-Golmud Expressway showed a moderate particle-size distribution, ranging from silt (8 ~ 4Φ) to boulders ( < - 8Φ). Their mass composition was dominated by fine sand (3 ~ 2Φ), fine gravel (- 1 ~ - 2Φ), and medium gravel (- 2 ~ - 6Φ), with an average gravel coverage of 70.42%. Wind and sand observations and calculations showed that the sand-moving winds along the Liuyuan-Golmud Expressway were mainly NNW, WNW, and W. The average wind speed, sand-moving wind frequency, sand drift potential (DP), resultant drift potential (RDP), maximum possible sand transport quantity (Q), and resultant maximum possible sand transport quantity (RQ) were higher in spring and summer and lower in autumn and winter. The resultant sand transport directions were mainly E, ESE, SE, and SSE. In the Da Qaidam, Fushaliang, and Golmud sections, the angles between the blown sand transport direction and the road alignment were relatively large (60.9 ~ 75.0°), and blown sand hazards were severe. Targeted prevention and control measures should therefore be adopted for these sections. Spring and summer are the key periods for blown sand prevention and control, and the western side of the expressway is the main area requiring protection. These results provide a reference for the prevention and control of blown sand hazards on expressways.

The Sichuan-Tibet Railway passes through windy and sandy areas in the river valleys of the southern Tibetan Plateau. Currently, the wind dynamic environment, sand material characteristics, and transport laws along the route are not well understood, hindering targeted sand control efforts. Through installing meteorological stations in the four wind-sand hazard sections along the route, respectively, key factors such as wind speed, wind direction and humidity that affect the dynamic process of wind-sand were observed, and sand samples were collected for particle size analysis. It is found that the average wind speed, sand-moving wind frequency, sand drift potential (DP), resultant drift potential (RDP), maximum possible sand transport quantity (Q), and resultant maximum possible sand transport quantity (RQ) are highest in spring (February to April). The predominant wind directions throughout the year are E, SSE, and ENE. Overall, the railway line is characterized by a low wind energy environment (DP ≤ 200 VU), and the directional variability index is moderate (0.3 < RDP/DP < 0.8). Sand materials are primarily fine sand (2–3 Φ) and medium sand (1–2 Φ). The key period for wind-sand hazard prevention and control is spring. The wind-sand prevention and control of the railway should focus on blocking (sand) and consolidating (sand), using external barriers and internal consolidation (distant blocking and near consolidation). Simultaneously, sand-fixing vegetation should be cultivated to establish a comprehensive protection system. To ensure the smooth operation of railway and the safety of train operation. The findings provide a scientific basis for the prevention and control of wind-sand hazards along the Sichuan-Tibet Railway.

Sand disasters significantly restrict ecological restoration and the development of sustainable transport infrastructure in desert areas, and the impact of varying subgrade width and roughness caused by different types and uses of routes on the wind-sand environment is still unclear. To address this, four typical subgrade widths were studied, and wind tunnel experiments were carried out using models. Near the ground surface (at heights < 8.3 cm), a 3.5 cm wide subgrade had a greater effect on the windward wind speed compared with three other widths. The distance required for wind speed recovery on the leeward of the 3.5 cm wide subgrade was greater than that for the three other widths. The 3.5 cm wide subgrade had a larger effect range and extent on the leeward wind flow field compared with the three other widths. The distance needed for the leeward wind flow field to recover at the 3.5 cm wide subgrade was also greater than that for the three other widths. The sand transport rates for the 14, 26, and 41 cm wide subgrades were similar and showed a consistent trend. However, the sand transport rate for the 3.5 cm wide subgrade was more variable and was lower than that for the three other widths at near-ground surface heights but higher at intermediate heights. Width has a minor effect on the wind-sand environment around the subgrades compared to roughness. The research findings provide insights into the relationship between the subgrade width, roughness, and wind–sand environment, offering guidance for mitigating sand disasters along transportation routes. It provides theoretical support for optimizing transportation infrastructure design, promoting green and low-carbon construction, and promoting ecological restoration around the routes.

The desert-steppe transition zone at the southern edge of the Hobq Desert features complex topography and frequent wind/sand activities. To explore the impact of different underlying surfaces and topography on the wind-sand environment in this area, field measurements were conducted to analyze the temporal and spatial variations of sand-moving wind conditions and sand drift potential. The results indicate that the average wind speed, sand-moving wind frequency, sand drift potential and sand transport rate in this area were higher in spring and winter than in summer and fall temporally. Spatially, different underlying surfaces and topographic conditions, the characteristics of the average wind speed, sand-moving wind frequency, sand drift potential and sand transport rate were as follows: quicksand surface > grassland surface > shrub surface, and top of slope > quicksand surface > middle of slope. The predominant annual wind directions and sand-moving wind directions were W, WNW and NW. The sand drift direction was towards the E or ESE in winter and spring. This study provides a theoretical basis and scientific support for the development of targeted sand control measures in the desert-steppe transition zone at the southern edge of the Hobq Desert, thereby maintaining regional ecological sustainability.

South Tibet expressways are built in the Yalu Tsangpo valley along the route to high-altitude and cold–temperature valleys, which are the main environmental characteristics of the region. Given that the blown sand environment and its potential harm are unclear, targeted prevention and control are not conducive, but its absence would result in severe wind–sand hazards on these expressways. In this research, the blown sand environment of the South Tibet Valley and the mechanism of sand damage to expressway bridges were studied via field observations, wind tunnel experiments and numerical simulations. The sand–moving wind is mainly west wind. The sand–moving wind frequency, sand drift potential, and maximum possible sand transport quantity are high in winter and spring (November–April) and low in summer and autumn (May–October). The sand drift direction is in the east direction. Expressway bridges have a considerable impact on the near–surface blown sand environment, forming a zone for increasing the wind speed between the top of the slope shoulder of the windward side of the bridge to the center of the bridge abutment, forming a zone for weakening the wind speed between the − 3 H distances of the upwind direction to the bottom of the slope middle of the windward side of the bridge, further forming a zone for weakening the wind speed centered in the slope shoulder of the leeward side of the bridge. The wind speed within a distance of 40 H downwind direction of the bridge generally did not recover. The wind–sand flow is partially blocked when it passes through the bridge and accumulates near the bridge, which cause harm. The impact of the bridge on the blown sand environment in the downwind is greater than that in the upwind. The results of this study can provide a reference for preventing and controlling wind–sand hazards on South Tibet expressways.

The Shannan wide valley section of the Sichuan–Tibet Railway is located in the middle reaches of the Yarlung Zangbo River, where sand hazard is severe. A wind tunnel simulation experiment was conducted by establishing a subgrade model and performing field observation to carry out research on the dynamic environment of blown sand and the sand hazard formation mechanism of subgrade in the Shannan wide valley. Observation results showed that the sand-moving wind of the Shannan wide valley was chiefly derived from the ENE direction, and the resultant sand transport direction was WSW. Wind speed, the frequency of sand-moving wind, the sand drift potential, and the maximum possible sand transport quantity were relatively high in the spring. Meanwhile, the dynamic of the wind-blown sand flow was further enhanced in the spring, particularly influenced by the flow action of the Yarlung Zangbo River. Thus, sand hazard mainly occurred in the spring. The Sichuan–Tibet Railway subgrade evidently changed the wind speed, the wind-blown sand flow field, and conditions of transport and accumulation. Within the distance of 5 times the model height in the windward direction and at the subgrade top center to 20 times the model height of the leeward direction was the wind speed deceleration zone, resulting in sand particle sediments. A wind speed acceleration zone appeared on the subgrade windward slope shoulder, resulting in wind-blown sand flow erosion. This study provides a scientific basis for sand hazard prevention and control in the Sichuan–Tibet Railway.

Bridges and subgrades are the main route forms for expressways. The ideal form for passing through sandy areas remains unclear. This study aims to understand the differences in the influence of expressway bridges and subgrades on the near-surface blown sand environment and movement laws, such as the difference in wind speed and profile around the bridge and subgrade, the difference in wind flow-field characteristics, and the difference in sand transport rate, to provide a scientific basis for the selection of expressway route forms in sandy areas. Therefore, a wind tunnel test was carried out by making models of a highway bridge and subgrade and comparing the environmental effects of wind sand on them. The disturbance in the bridge to near-surface blown sand activities was less than that of the subgrade. The variation ranges of the wind speed of the bridge and its upwind and downwind directions were lower than those of the subgrade. However, the required distance to recover the wind speed downwind of the bridge was greater than that of the subgrade, resulting in the sand transport rate of the bridge being lower than that of the subgrade. The variation in the wind field of the subgrade was more drastic than that of the bridge, but the required distance to recover the wind field downwind of the bridge was greater than that of the subgrade. In the wind speed-weakening area upwind, the wind speed-weakening range and intensity of the bridge were smaller than those of the subgrade. In the wind speed-increasing area on the top of the model, the wind speed-increasing range and intensity of the bridge were smaller than those of the subgrade. In the wind-speed-weakening area downwind, the wind speed weakening range of the bridge was greater than that of the subgrade, and the wind speed-weakening intensity was smaller than that of the subgrade. This investigation has theoretical and practical significance for the selection of expressway route forms in sandy areas.