トンネルの設計および供用におけるリスクベースのアプローチ

抄録

Public attention has been focussed on the safety of travel through road and rail tunnels recently, due to the recent tragic accidents which have claimed hundreds of lives. Many consider tunnel safety to be based in the provision of mitigation systems, but examination of the facts and issues surrounding tunnel travel show that the problems and solutions are related the basic civil engineering design.
The achievement of an appropriate level of safety for tunnel users requires a balance between the requirement to simplify the design and operation of the tunnel and the necessity to provide safety systems, such as cross passages and ventilation, which may have very significant effects on the civil design. These systems are expensive and are not always appropriate, depending upon the length of the tunnel, traffic types and hazards to users.
In order to rationalize tunnel safety design, risk based methods are increasingly used. This paper describes the issues surrounding a risk based design methodology and discusses some of the major factors which effect the civil and mechanical design of tunnels and tunnel systems. In particular, the choice of single or twin bore rail tunnels, means of escape, design fires and ventilation are highlighted, using examples from current projects.