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.
Desulfurized manganese residue (DMR) is an industrial solid residue produced by high-temperature and high-pressure desulfurization calcination of electrolytic manganese residue (EMR). DMR not only occupies land resources but also easily causes heavy metal pollution in soil, surface water, and groundwater. Therefore, it is necessary to treat the DMR safely and effectively so that it can be used as a resource. In this paper, Ordinary Portland cement (P.O 42.5) was used as a curing agent to treat DMR harmlessly. The effects of cement content and DMR particle size on flexural strength, compressive strength, and leaching toxicity of a cement-DMR solidified body were studied. The phase composition and microscopic morphology of the solidified body were analyzed by XRD, SEM, and EDS, and the mechanism of cement-DMR solidification was discussed. The results show that the flexural strength and compressive strength of a cement-DMR solidified body can be significantly improved by increasing the cement content to 80 mesh particle size. When the cement content is 30%, the DMR particle size has a great influence on the strength of the solidified body. When the DMR particle size is 4 mesh, the DMR particles will form stress concentration points in the solidified body and reduce its strength. In the DMR leaching solution, the leaching concentration of Mn is 2.8 mg/L, and the solidification rate of Mn in the cement-DMR solidified body with 10% cement content can reach 99.8%. The results of XRD, SEM, and EDS showed that quartz (SiO2) and gypsum dihydrate (CaSO4·2H2O) were the main phases in the raw slag. Quartz and gypsum dihydrate could form ettringite (AFt) in the alkaline environment provided by cement. Mn was finally solidified by MnO2, and Mn could be solidified in C-S-H gel by isomorphic replacement.
The desulfurized electrolytic manganese residue (DMR) was prepared by calcination and desulfurization of industrial waste electrolytic manganese residue, and the original DMR was ground to prepare DMR fine powder (GDMR) with specific surface areas of 383 m2/kg, 428 m2/kg, and 629 m2/kg. The effects of particle fineness and content of GDMR (GDMR content=0%, 10%, 20%, 30%) on the physical properties of cement and the mechanical properties of mortar were studied. After that, the leachability of heavy metal ions was tested, and the hydration products of GDMR cement were analyzed using XRD and SEM. The results show that the addition of GDMR can regulate the fluidity and water requirement for the normal consistency of cement, delay the hydration process of cement, increase the initial setting and final setting time of cement, and reduce the strength of cement mortar, especially the strength of early age mortar. As the fineness of GDMR increases, the reduction of bending strength and compressive strength decreases, and the activity index increases. The content of GDMR has a significant effect on short-term strength. With the increase in GDMR content, the strength reduction degree becomes higher and the activity index decreases. When the content of GDMR was 30%, the 3D compressive strength and bending strength decreased by 33.1% and 29%. When the content of GDMR in cement is less than 20%, the maximum limit of leachable heavy metal content in cement clinker can be met.
13 June 2024 in Measurement Science and Technology
Expressways in desert areas are prone to sand lifting and accumulation. This study aims to explore the impact of various risk factors on sand accumulation on road surfaces. Initially, the study identifies the causes of these risks through on-site investigation. Subsequently, using Fluent numerical simulation, it examines how different wind speeds, wind directions, route angles, embankment heights, embankment widths, embankment slope ratios, and central median layouts affect sand accumulation. Finally, based on simulation results and sand accumulation data from the Uma Expressway’s desert section, the study evaluates the importance of these factors using ordered logistic regression analysis and proposes strategic recommendations. The findings indicate that the degree of sand accumulation increases with higher wind speeds, more significant embankment heights, and variations in wind direction, route angle, and embankment width, as well as the configuration of the central median. Wind speed and embankment height are identified as the main factors influencing sand accumulation. Based on the risk assessment, the study suggests a four-point preventive strategy: (i) implementing wind speed management measures; (ii) optimizing embankment design; (iii) developing sand prevention strategies for the central median; and (iv) adjusting the alignment of the road relative to the wind direction.
Existing research on road safety mainly focuses on normal driving conditions, and seldom considers the impact of poor environment on driving safety. This study focuses on the braking safety of vehicles under sandy road conditions, combines the theories of traffic engineering and cardiophysiology, Through the real vehicle test, the cardiophysiological data of drivers braking under different conditions (including different road alignment, different braking speeds, and different road sand thicknesses) are collected, and the average of the heart rate growth rate and EEG data are analyzed in the process of braking, so as to determine the critical hazardous state of the braking under the condition of sandy roads. The results of the study show that: under different road linear conditions, braking in the combined section of curved slopes is the most dangerous, and the average value of heart rate growth rate of the driver is 26.3%, and the average value of PSD integral value of EEG α/β is 0.68, which is in the state of nervousness; under the conditions of different braking speeds, the heart rate growth rate of the driver is more than 27% of the nervousness threshold, and the ratio value of EEG α/β wave is less than 1, which is the same as that of EEG α/β wave. The ratio of EEG α-wave to β-wave is lower than 1, and the degree of alertness is higher; under the condition of different road surface sand thickness, when the thickness of road surface sand is 0-2mm, the average value of the driver’s heart rate growth rate is the maximum of 26.2%, the braking distance is increased obviously, and the α/β is reduced significantly, and the driver has a potential safety problem. The results of the study are of great significance to improve the safety of driving on desert highways and reduce the risk of accidents.
In order to reduce the fluctuations of traffic flow and the impacts of traffic flow fluctuations, thereby increasing the level of service of roads and constructing the Internet of Things-based traffic system, based on the various causes of traffic flow fluctuations, the countermeasures were taken, such as the optimization of lanes, the management of intersections, the improvement and perfection of slow-vehicle lanes and bus stops, the timely renewal of traffic signs and marks, the rational arrangements of road operations, and the removal of visual obstacles, etc. The research results showed that these countermeasures could effectively reduce the hidden peril of accidents and improve the road capacity, thereby improving the level of service of roads, which provided a theoretical foundation and basis for road engineering design and traffic management. It can be seen that improving urban traffic through rational management and control measures can effectively improve the level of service of urban traffic.