chapter  3
Tunnel Requirements
Pages 15

The Traffic tunnels are provided for the purpose of transportation of goods and people and their requirements can be broadly classified as operational, structural, Constructional and maintenance. The cross-sectional profile of the tunnel has to allow movement of the largest vehicle it is designed for and provide for some additional safety margin. For railways, even if separate tunnels are not available, the wheel guidance available and the additional guard rails installed between rails provide the necessary safety. Curvature in railway tunnels depends on speeds to be permitted on the section and the gauge of the line. Aerodynamic problems in railway tunnels arise due to piston action of the train through a narrow tube. Type of soil, end use and construction methodology govern the choice of shape of tunnel. Water supply tunnels are provided for conveying water from storage reservoirs or streams to the treatment plants or ground storage at distribution centres across an undulating country.