Horizontal Alignment Safety Design Of Urban River-Crossing Tunnel

River-crossing tunnels have gradually become an important media that strengthens the connection of both sides of the river channel,because it is not affected by the climate.But at the same time,river-crossing tunnels usually cause more accidents and lead to severer consequence,since the alignment often accompanies with downhill and uphill and goes across the river.Therefore,how to optimize river-crossing tunnel alignment design,and improve the security of river-crossing tunnel and reduce the loss caused by traffic accidents,is a problem to be solved.This study firstly analyzed the spatio-temporal distribution characters based on accident data collected from Shanghai river-crossing tunnels.Then,Logistic model was applied to investigate the relationship between factors and accident severity.These factors covered 9 aspects,including time of accidents,weather conditions,place of accidents,type of vehicles,tunnel length,number of lanes,speed limit,and radius.According to the geometry features and results of safety analysis,the river-crossing tunnel alignment design model was developed.Construction cost,location-dependent cost,safety cost and consistency cost were considered as objective function.Then,genetic algorithms were applied to get the optimal solution by using straight mutation operator,arithmetic crossover operators etc.This study explored the characteristics of accidents in river-crossing tunnels,and then dug out variables that are related to the safety performance of the tunnel.The horizontal alignment optimization model was developed to improve the safety.This study can provide a new approach to alignment design.