The Research On Alignment Safety Of Curved Slope Section Based On Operating Speed And Vehicle-Road Coupling

The mountain road is restricted by the complicated terrain and the engineering cost and so on,there will inevitably appear many curved and slope sections with poor alignment index.In addition,the related specification of road alignment design in our country is a single linear index standard based on the design speed at present,the influence of different combination of horizontal and longitudinal lines on the operating speed of vehicles in curved and slope sections and the requirements of the dynamic changes of actual operating speed on the design of alignment are ignored.The purpose of this paper is to provide a reference for the safety index design of different alignment combinations of mountain road curved slope sections from the angle of vehicle-road coordination and combined with the actual operating speed characteristics of mountain road curved and slope sections.The research object of this paper is the curved slope section of the second grade and the second grade road in the mountain area.Firstly,by analyzing the driving force and stability of the vehicle driving on the curved,slope and curved slope combination section,the coupling safety model of the vehicle and the road is obtained.Then,according to the relevant norms and research,the operating speed prediction model of bend and ramp is established,and the operating speed prediction model of three kinds of curved slope combination line is established according to the actual investigation and statistical analysis.Then the operating speed prediction model is combined with the vehicle-road coupling safety model,the main safety design index threshold and the law of change with design parameters of bend,steep slope section and combined road section are obtained by selecting appropriate vehicle model and model parameters to substitute in the model.Then the stability of the vehicle under different working conditions is simulated and analyzed by Carsim,which verifies the rationality of the model and the law of the change of the design threshold to a certain extent.The results show :(1)The larger the operating speed of the vehicle in the bend section is,the larger the corresponding limit safety radius is;The larger the ramp turn supperelcvation is,the smaller the corresponding limit safety radius is;In general,the limit safety radius of a small car is smaller than that of a large vehicle,but when the design speed is less than 40km/h,the limit safety radius of a small car is larger than that of a large vehicle.(2)When the vehicle is driving on the curved-slope section,the faster the operating speed is,the shorter the maximum safety slope length is,and the larger the slope is,the shorter the maximum safety slope length is;The smaller the ramp turn supperelcvation of the first line element is,the shorter the maximum safety slope length is;On the whole,the maximum safety slope length of curved-slope section is shorter than that of single longitudinal slope code.(3)When the vehicle runs on the curved slope combined road section,the greater the operating speed is,the smaller the corresponding limit safety radius is,the larger the ramp turn supperelcvation is,the larger the corresponding limit safety radius is,and the slope has little effect on the radius;Under the same condition,the minimum safety design radius of the bending slope combination III is larger than the bending slope combination II,the bending slope combination II is larger than the bending slope combination I,moreover,the design radius of the three kinds of curved slope combinations is greater than the corresponding standard minimum radius;Finally,the design method of line continuity for the curved road section of mountainous road and the design of safety facilities suitable for mountain road’s curved slope section are put forward.The research results of this paper can be used as a reference for the selection of line design index threshold and the operating speed characteristics of different road sections with different bending and slope combination forms in mountain areas.It is of some significance to improve the continuity and safety of curved slope section of mountain road.