Safety Requirements in a Tunnel

Safety Requirements in a Tunnel

• Emergency exits in about 250 m intervals
• Lay bays in about 1000 m intervals
• Emergency niches in about 150 m intervals
• Fire fighting niches in about 150 m intervals

Tunnel Lighting

• To allow traffic to enter, pass through and exit the enclosed section safely
• Good tunnel lighting allows users to enter, pass through and exit the enclosed section safely and comfortably.

Tunnel Drainage

• In the tunnel, driving water comes from the following sources. They are

             1.wash water during washing drill holes and

 2.ground or subsoil water

There are three types of drainage

    1. pre-drainage

     –is to prevent the entry of water into tunnels before starting construction.

    2. dewatering

     –is the removal of water during construction

3.permanent drainage

    –permanent drainage is to remove water after completion of construction

Pre-drainage

• Where seepage is small and water comes down from the tunnel roof
• Water is made to flow over a temporary pitched roof of corrugated sheets on to the longitudinal side drains
• Pre-drainage essentially consists of preventing the surface water adjoining the tunnel interfering with the construction work

• Where seepage is small and water comes down from the tunnel roof
• Water is made to flow over a temporary pitched roof of corrugated sheets on to the longitudinal side drains
• Pre-drainage essentially consists of preventing the surface water adjoining the tunnel interfering with the construction work

De-watering

• Pumping method
• The quantity of water that accumulates is collected in sump wells and pumped out of the tunnel
• When the tunnel is long, it may be necessary to have more than one sump well (at 300m to 500 m intervals)
• Sump wells also help in the settlement of solid materials

Permanent Drainage

• By constructing drainage ditches longitudinally sloping towards the portals or shafts, from where they could be pumped out of the tunnel by suitable pumps

TRACK ALIGNMENT

• The direction and position given to the center line of the tunnel are called track alignment.

              –Horizontal alignment- width, deviations in width and horizontal curves

              –Vertical alignment- change in gradients and vertical curves

• A new track must be aligned very carefully as improper alignment will result in a capital loss in initial cost or recurring loss in maintenance.
• Once a track has been aligned or constructed it is difficult to change the alignment due to the increase in the cost of adjoining land and construction of costly structures at that location by the side of the railway line.

BASIC REQUIREMENTS OF GOOD ALIGNMENT

• Purpose of track
• Feasibility(meets all requirements)
• Economy
• Safety
• Appearance(borrow pits ,transition curves)