Study On Alignment Design Method Of Low Grade Roads In Mountainous Areas Based On Operating Speed

Whether highway alignment indicator is reasonable not only directly affects the setting of the structures, the extent of damage to the environment and the construction costs, but also related to the safety of drivers and passengers. There are closely relationship between road alignment and road safety, which is particularly reflected in low-grade roads. in mountainous areas. Comparaed to the plain areas, the topography, geology, hydrology and other natural conditions in mountainous are complex,and there are larger ecological constraints, many limitations and. influencing factors. These various disvantages for driving in mountainous areas make the condition that the low grade road in mountainous areas have strict requirements for the alignment quality.The alignment quality plays a decisive role in driving features,such as safety, economy, comfort and capacity. Therefore, the reasonable selection and use of the indicators of route design is crucial to build a road which has the characters such sa safety, comfort, rationality of economic engineering and good adaption to the surrounding environment in mountainous areas.The theory of operating speed is used for the assessment of alignment quality in this paper in order to achieve the reasonable coordination of the highway alignment elements and design speed. It can decide the various indicators of the route through checking and modifying the Initial route according to the operating speed requirement.The main contents of this paper:①The significance of evaluation on alignment quality in Mountainous low-grade road at design stage and research status of evaluation on alignment quality based on the theory of operating speed at home and abroad.②The conception and influencing factors of operating speed is expounded。Study on the concrete application of the theory of operating speed of the highway alignment design in China's specific application.③The prediction of operating speed. According to the characters of operating speed in mountainous low grade road ,determining the principle of dividing paragraphs and predicting the operating speed on different paragraphs by means of the theory method based on the full study of achievements about operating speed evaluation at home and abroad. At the same time, the influence of factors ,such as traffic volume, the proportion of large vehicles, road width, flat horizon, climate, landscape disturbance and slip entrance,on operating speed is considered. Then the prediction model for different paragraphs of mountainous low grade road and the calculation program of operating speed which is compilated by use of VB was obtained.④Combining with mature evaluation criteria and methods for alignment at home and abroad,a suitable evaluation standards and methods for mountainous low-grade highway are determined.⑤Bring the evaluation method of highway alignment for mountainous low-grade highway into exercise,to find the inconsistency of entire route ,check and modify the initial route by use of the prediction results and the evaluation criteria of oprating speed,in order to achieve the reasonable collocation of elements of highway alignment with design.