针对由山区高速公路纵坡坡度和坡长组合设置不合理,导致长大纵坡路段交通事故频发的问题,通过分析重型车辆上下坡运行速度特性及受力情况,以陕汽生产的F3000重载汽车为例,通过理论推导构建重型车辆公路纵坡爬坡及下坡车速与坡长理论模型,模拟不同比功率重型车辆上、下坡运行速度与坡长的变化关系,并确定高速公路合理的上下坡临界坡长。研究中假设工况为高速公路坡度1%~6%,上坡车辆最高初速度和最低末速分别为80、50km/h,下坡最低初速度和最高末速度为0、80 km/h。使用MATLAB模拟计算其坡度与车速的变化规律。研究结果表明:上坡过程中,以80km/h的初速度为例,稳定车速为45~61km/h;当坡度一定时,比功率越大的车型速度降低的越快,稳定行驶速度越大,达到稳定行驶车速的平衡坡长越长。下坡过程中,当坡度一定时比功率越大的车型,车速增大越多,稳定行驶速度越大,达到稳定行驶车速的平衡坡长就越短。在坡度为1%~3%时,无须设置爬坡车道;当坡度大于3%时,比功率较低的车型,爬坡性能较差,车速下降较快,需要设置爬坡车道。重型车辆在4%、5%、6%的坡度行驶时,设置避险车道的坡长阈值分别为5.5、4、3 km。研究成果可为山区公路线形的合理设计、道路的安全防护以及爬坡车道与避险车道的设置提供理论依据,从而提高山区高速公路重型车辆的行车安全。
Aimed at the unreasonable combination of different lengths and grades of slopes of expressway in mountainous areas have led to an increase in traffic accidents on long and steep slopes. A model was designed to explore the relationship between the heavy-vehicle speed characteristics and slope length after analyzing the speed and stress distribution in moving uphill and downhill taking F3000 heavy-haul vehicle produced which by Shaanxi automobile company as an example. The reasonable critical slope length was determined by simulating the relationship between the speed of heavy vehicles with different specific power and the slope length during uphill and downhill. The research scenario was assumed that the slope of the expressway was 1% to 6%, the initial speed of uphill was 80 km/h and the final speed range was 50 km/h, and the initial speed of downhill was 0 km/h and the final speed was 80 km/h. The relationship between the slope and the speed was calculated through MATLAB simulations. The results show that when going uphill, if the initial speed is 80 km/h, the stable speed is 45 to 61 km/h. When the slope is constant, the higher the specific power of the heavy vehicle, the faster is the decrease in the speed, and the larger the stable speed, the longer is the equilibrium slope required to achieve stable speed. In the downhill process, when the slope is constant, the higher the specific power of the heavy vehicle, the greater the speed increase, the higher is the increase in speed, and further, the greater the steady operation speed, the shorter is the equilibrium slope length to reach the final driving speed. It is not necessary to set a climbing lane when the grade is 1% to 3%. When the slope is greater than 3%, the speed decreases fast for lower specific power of vehicles with a poor climbing performance. It is therefore required to set up a climbing lane or other safety facilities to increase road safety. When heavy vehicles run in the 4%, 5%, and 6% slope range, the thresholds for setting escape lanes are 5.
JOurnal of Chang’an University:Natural Science Edition