Study On The Combination Design Optimization Of Slope And Slope Length Of Continuous Uphill Section Of Secondary Highway

Secondary roads are important types of highways in my country’s transportation system.They are widely found in primary and secondary trunk roads and branch roads in towns or suburbs,and play a role in connecting important cities and their administrative units.With the rapid development of my country’s urban and rural regional economy,the transportation links between towns and counties are increasingly strengthened,and the demand for secondary roads in my country will continue to increase in the future.Nowadays,in order to improve transportation efficiency and reduce transportation costs,the actual load of trucks has increased significantly,which seriously reduces the climbing performance of trucks and has a certain impact on the traffic volume of continuous uphill sections.At present,the design units mainly use the method of extending routes or adding climbing lanes to solve such problems,but both methods increase the construction cost and occupy more land resources.The optimized design of the combination of longitudinal slopes of the road can not only improve the climbing performance of trucks,increase the climbing speed of trucks,but also save construction costs and avoid the installation of climbing lanes.Specific reference standards.After on-site investigation and reference to relevant literature,priority was given to the adoption of Dongfeng truck EQ1228V19D2 as the leading model of large trucks.Then combined with the driving theory of the vehicle to analyze and deduce the dynamic performance of the dominant car during the climbing process,the theoretical calculations can obtain the maximum speed,the critical speed,and the shift speed of each gear of the dominant car,determine the balance speed and balance slope length,and The climbing performance curve of the vehicle is drawn,and the climbing speed of the truck is mainly affected by factors such as mass-to-power ratio,slope,slope length,longitudinal slope combination mode,and entry speed.Then use simulation software Trucksim to establish vehicle model,driver model and road model,and verify the reliability of the model.Then,through the design of two simulation experiment schemes of the leading truck models in the continuous uphill section climbing process,the built simulation model is used to discuss the optimal combination and specific value range of the longitudinal slope design of the continuous uphill section of the secondary highway: one is the longitudinal slope Combined simulation experiment to study the combination form of longitudinal section that is most beneficial to the climbing of trucks,and use this combination as the recommended combination at the design speed;the second is the basic unit limit simulation experiment,which clarifies the selection of the recommended longitudinal combination at each design speed Value range.Finally,the longitudinal section design data of a continuous uphill section of a secondary highway in Dianjiang County,Chongqing City were selected,and the conclusions were used to optimize the longitudinal section design,respectively simulating the climbing speed before and after optimization of the leading truck model,and comparative analysis of the improved front and rear speeds The difference between the two,to verify the validity of the recommended value of the combination of the longitudinal slope of the secondary highway.Through the research and analysis of this paper,the main factors affecting the climbing speed of the leading truck models are clarified,and it is proposed that when designing the longitudinal section of the continuous uphill section of the secondary highway,the recommended combination of gentle slope to steep slope or steeper slope to steep slope should be preferred.At the same time,it is necessary to ensure that the absolute value of the difference between the front and rear slope sections is small,and avoid the recommendation of the slope limit value.At the same time,the specific value range of the recommended combination of longitudinal slopes at various design speeds of secondary highways is also proposed.The use of the recommended combination of longitudinal sections is more conducive to the climbing of trucks.The research in this paper makes up for the inadequacy of the standard research on this kind of problem,and provides convenience for road designers in the design of longitudinal profile,and has certain engineering application value.