The document discusses drainage systems for tunnels. It explains that drainage systems control water entering tunnels during and after construction by preventing excess water and removing what does enter. Water comes from wash water used during drilling and groundwater. Drainage systems are either temporary, using open ditches or pumping, or permanent, including central drains, corrugated roofing with side drains, or single side drains. Central drains use a sloped drainage ditch to move water towards portals for pumping. Single side drains are suitable when tunnels only require a single lane and use a single large drain. Open ditches are simplest but work best in impervious soils and rock. Pumping systems collect water in sumps and use piston or
2. • Drainage of tunnel’ means controlling of water
during and after the construction of the tunnel.
• Controlling of water is attained by preventing
excess quantity of water from entering the
tunnel and removing the water that does enter.
• In driving a tunnel water comes from two
sources
1) Wash water used for washing drill holes.
2) Ground water or sub soil water.
3. • Drainage system is divided
1. Temporary Drainage system
a) Open ditch drainage system
b) Pumping system
2. Permanent Drainage system
a) Central drain system
b) Corrugated sheet roof with side drains
c) Single side drain system
4. Central drain system
• This system is suitable when the water coming
through the roof and the side walls of the tunnel is
sufficiently low.
• In this system a central drainage ditch is
constructed longitudinally sloping towards the
portals from where they could be pumped out of
the tunnel by suitable pumps
5. Single side drain system
• This system is adopted where the quantity
of water entering the tunnel is small.
• The method is adopted in case of tunnels
carrying a single lane highway or railway
track.
• For a draining water a single side drain of
sufficient capacity is provided.
6. Open ditch drainage system
• This is the simplest method through which
water may be moved i open ditches, with
proper slopes, to the portals and may be
pumped out from there.
• It is suitable in impervious soils and rock
bases.
7. Pumping system
• In case of pumping system the quantity of
water that accumulates is collected in
sump wells and pumped out of the pump.
• For long tunnels, it may be necessary to
have more than one sump used.
• There are two types of pumps used
1. Piston type
