Radius and widen value of circle curve of highway pioneer road
In order to supplement the design indicators for pioneer road alignment,improve the quality of pioneer road construction and ensure transportation safety,starting from the characteristics of pioneer road transport vehicle,radius and widen value as two key parameters were studied.Firstly,four representative vehicles were selected,excavators,dump trucks,semi-trailer trains,and beam carriers by investigating the construction situation of pioneer roads in 9 expressway and 1 provincial road projects in China.Subsequently,the space passing ability of vehicles was calculated based on the relationship between the vehicle structure and the road geometry,and the required widening values and radius passing ability limits for dump trucks,semi-trailers,and beam carriers were obtained,a lateral stability verification method was proposed based on the backward shift of vehicle gravity center for dump trucks and semi-trailer trains.Finally,a comparison was made between the radius values of circular curves under the different superelevation of lateral stability constraints for two types of pioneer roads with different lateral friction coefficients(0.3 and 0.8),and the radius values were calculated using the pavement friction coefficient.Key indicators for horizontal curves corresponding to representative vehicle models were recommend and can be used as a reference for pioneer road design.The results show that the radius passing ability limits for dump trucks and semi-trailer trains are 12 m,48 m for monolithic beam carriers,and 14.5 m for towed type beam carriers.There is a significant difference in the required pioneer road radius and widen values for specific vehicle types.The main factors affecting vehicle lateral stability are speed,center of gravity position,and pavement friction coefficient.In the condition of a lateral friction coefficient of 0.3,vehicles are more prone to lateral sideslip,while in the condition of a lateral friction coefficient of 0.8,vehicles are more likely to lateral rollover.The minimum radius value can be significantly reduced by increasing the superelevation,with little impact on lateral stability.The turning radius of dump trucks and semi-trailer trains calculated by lateral force coefficients both meet the requirements for lateral stability.9 tabs,10 figs,26 refs.
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