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山区高速公路长大下坡路段缓坡设计指标

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为了明确中国山区高速公路长下坡缓坡设计指标,在汽车动力学理论的基础上,以六轴铰接列车为主要研究对象,剖析其以发动机辅助刹车方式长下坡时的货车加速特征与制动毂散热特征.首先,建立力学平衡方程,构建挡位-速度-临界坡度模型,求解不同速度和挡位条件下的缓坡临界坡度值.然后,进一步考虑中国高速公路设计控制条件与货车行驶特性,以12挡和11挡时对应的临界坡度作为高速公路缓坡设计控制指标,提出连续下坡缓坡设计指标与方法;最后,以进入缓坡速度70 km/h为例,对比基于降速及降温特性得到的缓坡坡长指标,并结合西南某山区高速公路进行方案设计优化及优化效果分析.研究结果表明:连续长下坡路段之间设置缓和坡段有助于制动毂降温,恢复货车制动性能;基于速度特性得出了速度折减值10和20 km/h不同缓坡坡度下的缓坡坡长值;基于降温特性求解的缓坡坡长以制动毂失效温度260 ℃为最不利条件,并得出了不同运行速度及温度折减值;基于降速特性得到的缓坡坡长值对纵坡设计具有指导意义,而基于降温特性得到的缓坡坡长值相对较大,不宜作为设计参考但可作评价研究,并整理得到连续长下坡缓坡设计-评价流程,以西南山区某高速公路为实例分析发现,对缓和纵坡的坡度与坡长合理取值能有效改善制动毂温度,提升连续长下坡路段车辆的行驶安全性.
Gentle slope design indexes of long downhill in mountainous expressway
In order to clarify the design criteria for extended downhill grades on mountainous highways in China,with a primary focus on articulated six-axle trucks,an analysis was conducted based on the principles of vehicle dynamics.The acceleration characteristics of trucks descending long slopes was examined,using engine-assisted braking and the heat dissipation characteristics of brake hubs.Initially,mechanical equilibrium equations were formulated,and a gear-speed-critical gradient model was developed to determine the critical gradient for gentle slopes under various speed and gear conditions.Subsequently,considering the design constraints of highways in China and the operational characteristics of trucks,the critical gradients corresponding to the 12th and 11th gears were adopted as the control indicators for highway gentle slope design.The design criteria and methods for continuous downhill and gentle slope sections were proposed.Finally,utilizing an entry speed of 70 km/h as an example,a comparison was made between the gentle slope length criteria obtained based on speed reduction and temperature reduction characteristics.Additionally,an analysis was performed,combining the results with an optimized design of a highway in the Southwestern Mountainous Region.The results show that introducing gentle slope sections between continuous long downhill segments contributes to brake hub temperature reduction and restoration of truck braking performance.Based on speed characteristics,different gentle slope lengths are determined for speed reductions of 10 and 20 km/h under varying gentle slope gradients.The gentle slope length based on temperature characteristics is calculated under the least favorable condition of brake hub failure temperature at 260℃,considering different operating speeds and temperature reduction values.The gentle slope length obtained based on speed reduction characteristics provides valuable guidance for longitudinal slope design,while the length obtained based on temperature reduction characteristics,although relatively large,is not suitable for design but can be used for evaluation.The continuous downhill and gentle slope design-evaluation process is summarized.Using a highway in the Southwestern Mountainous Region as an example,the analysis reveal that reasonable values for the gradient and length of gentle longitudinal slopes effectively improve brake hub temperatures and enhance the safety of vehicles traveling on continuous long downhill segments.6 tabs,7 figs,34 refs.

road engineeringdesign of transition slopeexperimental researchdownhill charac-teristics of truckcontinuous long downhill slopebrake hub temperature

张驰、王韩、富志鹏、侯宇迪、白浩晨

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长安大学公路学院,陕西西安 710064

中交第一公路勘察设计研究院有限公司,陕西西安 710075

广州市市政工程设计研究总院有限公司,广东广州 510095

道路工程 缓坡设计 试验研究 货车下坡特性 连续长下坡路段 制动毂温度

国家重点研发计划国家重点研发计划四川省科技计划四川省交通运输科技项目四川省交通运输科技项目陕西省自然科学基础研究计划

2021YFB26001032021YFB23016022022YFG00482019-ZL-122022-ZL-042023-JC-YB-391

2024

10.19721/j.cnki.1671-8879.2024.01.001

长安大学学报(自然科学版)
长安大学

长安大学学报(自然科学版)

CSTPCD北大核心
影响因子：1.011
ISSN：1671-8879
年,卷(期)：2024.44(1)
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