Economic of Tunnel based on
1. Nature of soil and rock
2. Requirements of fill
3. Depth of cut > 18 m – tunneling.
The position of the tunnel on the ground is called as tunnel alignment. Tunnel alignment can be horizontal or vertical. Horizontal alignment runs along the center of the tunnel and vertical alignment is used to define the changes in elevation of the tunnel. Before undertaking the tunnel, construction engineer must perform the tunnel alignment.
Features
A.) For increasing the quality and stability of the tunnel.
B.) It is used to reduce the number of transit trips.
C.) For reducing the impact of surface transit operations in different places.
Tunnel Alignment Depend on
1. Topography of particular area.
2. Various kind of environmental situation.
3. Entrance and exit point of specific area.
4. Alignment restraints.
Tunnel Alignment and Gradient
Tunnel alignment is very important step in tunnel making. If the calculation of tunnel alignment goes wrong then the tunnel would not meet at the end. While starting the work, the centerline is marked on the ground for giving the accurate length to the tunnel. After completed this process a survey is happened to ensure that the horizontal tunnel alignment and other levels are transferred to the underground position.