Research On Route Scheme For Reconstruction And Upgrading Project Of Beijing Section Of G109

At present,the full length of Beijing section of G109 is 119 km,with low grade and alignment indexes and small traffic capacity.It is difficult to assume the functions of the western exit of the capital and the national highway trunk lines,so it is required to be upgraded and constructed.However,the terrain,engineering geology and hydro-geological conditions are complicated,and there are lots of restrictions such as rivers,villages and towns,highways and railways and environmental sensitive points along the way.The project is huge in scale,significant in construction significance,sensitive in environmental impact and difficult in construction conditions.In order to realize the construction goal of “perfect function,safety and comfort,environment friendly and resource saving”,the comprehensive research should be carried out in the route planning.The main research methods and content are the followings.The four-stage traffic forecasting method is adopted to forecast the traffic composition and traffic volume in the characteristic year;The highway grade,design speed and main technical index standards are demonstrated from the aspects of road network function,traffic volume and construction conditions.;The international mainstream survey and design integration technology was adopted to optimize the route planning;The running speed and three-dimensional sight distance calculation method are used to evaluate the traffic safety;According to the number of projects and three-dimensional alignment,environmental impact and engineering economy are evaluated.The main research results include the followings.The predicted traffic volume in the characteristic year is 30,000 ~ 50,000 pcu / d,and the traffic composition is mainly small passenger cars.The reconstruction standard is a six-lane highway with a design speed of 80km/h.The valley belt of Yongding River and Qingshui River are designed into corridors.The main technical and economic indicators for the route recommendation scheme are as follows.The total length of the route is 66 kilometers.The minimum radius of the circular curve is 700 meters.The maximum longitudinal slope is 3.6%.The maximum longitudinal slope for three kilometers is 2.53%.The sub-grade earthwork is 10.14 million cubic meters.The bridge ratio is 56%.The total project cost is 14.9 billion yuan with the floor area of 6,630 mu.The traffic safety of the route is good.The ?V85 of full line is less than 20km/h.The linear index is balanced and continuous.The traffic sight distance condition is superior.The environmental impact of the route scheme is relatively small,which is about 60% of similar projects.The project cost is relatively low,which is about 70% of similar projects and saves 1170 mu of planned land.Through the research,it can concluded that the following conclusion are of great reference significance for the design of highway in mountain areas:1)Accurate functional position,reasonable traffic volume forecast and clear analysis of construction conditions are the basis for demonstrating highway route grade and main technical indexes.2)For the highway in mountain areas,optimizing corridor design is the key.It is suggested to carry out the route layout research on the phase of scheme according to the preliminary design depth and to reduce environmental influence and engineering cost through some measures such as linear optimization,flexible layout of road width,reasonable structure of roadbed and control of bridge ratio.3)Based on the integrated platform of survey and design,conducting the research on the route scheme by using advanced technologies such as DTM,curve design,real-time correlation optimization of road spatial alignment,and three-dimensional alignment simulation evaluation is an important mean to realize the overall goal of highway construction in mountain areas and to implement the development concept of “source-saving and environment-friendly” society.