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LIGHTNING IN TUNNEL

Observing new process followed in LIGHTING SYSTEM IN TUNNEL AND VENTILATION SYSTEM OF TUNNEL

Ventilation in Tunnel

The main objective to provide proper ventilation  in tunnel during tunnel operation are
  1. To supply fresh air to the working crew
  2. To remove injurious and obnoxious fumes and gases of explosion
  3. To safely remove the dust caused by drilling blasting and mucking

Natural and Mechanical Ventilation in tunnel:

When drift is driven from portal to portal it provides fair ventilation in tunnel during enlarging operations. In long tunnels, this natural ventilation is inadequate and mechanical ventilation
  1. Used when drift was driven from portal to portal
  2. Used when the tunnel is short and diameter long 
  3. If it is oriented along wind direction
  4. Its efficiency depends on alignment and grade of the flow of traffic

Volume of Air Consideration:

During working each worker should be supplied with 200 cu.ft to 500 cu.ft of fresh air. A compressed air used for the drills is usually contaminated with oil and dust when released from drills and not expected to be helpful. After each explosion, the near face is filled with fumes and dust and is fit for breathing. This foul air has to be exhausted replaced with fresh air before the workmen start removing the debris from the explosion. The time-lapse between exploding the charge and commencing mucking will be about 30 minutes within which time, the ventilating system should clear the tunnel and supply fresh air.

Mechanical Ventilation in tunnel

Mechanical ventilation in tunnel is provided by one or more electric fans or blowers which may blow fresh air into the tunnel or exhaust the dust and foul air from the tunnel. There are three system of ventilation 
  1. Blowing
  2. Exhausting
  3. Combination of Blowing and exhausting

1) Blowing or plenum process:

  1. Fresh air is blown 
  2. Fog occurs inside tunnel 
  3. Not suitable for the long tunnel as it is unhealthy with poor visibility            
  4.  Advantage of supplying fresh air near working                                                             

2)Exhausting or vacuum process:- 

  1. Quickly remove dust and smog                                                                               
  2. In this separate fresh air duct not reqd 
  3. Used for a short tunnel 
  4. Not provide uniform ventilation 
Exhausting and blowing process for ventilation in tunnel

3) Combination of exhausting and blowing process 

  1.  The most efficient technique in the ventilation system 
  2. 15 to 30 min exhausting is carried out 

Points to be kept in mind about Ventilation in Tunnel

Ventilation for passenger – Primary ventilation 
Ventilation for plants – Secondary ventilation
 1)Transverse ventilation system: Does not interfere with traffic and remove foul gas by the shortest way 
2)Semilateral system: Supply of fresh air through shaft instead of ventilation tube 3)Resonator: To reduce the noise level


Ventilation in tunnel

     
LIGHTING IN TUNNEL

Light intensity of 260 lumens per m² in working area is sufficient for proper and efficient
lighting 


Spacing of Lighting in tunnel depends on 

1) Dimension of work 
2) Size of light source
 3) Nature of rock surface

 Types of Lighting in tunnel
1) Lantern and lamp burning light – used during survey work 
2) Coal gas lighting – leakage in pipes
3) Acetylene lighting – not common 
4) Electro lighting – very popular lighting 
5) Flood lights – to have detailed inspection for any length of spot 

DUST PREVENTION IN TUNNEL

The various operation involved in tunnel excavation such as drilling,blasting, and handling muck cause dust accumulation in the tunnel atmosphere. This dust-laden air constitutes a serious health risk the dust concentration is limited. In rock tunnel particularly this hazard is very serious ass extended breathing of silica causes a dangerous lung disease known as siliceous which proves fatal.
To safeguard workers by permitting a limited dust concentration inside the tunnel which could be safe. 

DUST CONTROL IN TUNNEL 

The various methods used to minimize dust accumulation are:
  1. Wet Drilling
  2. Use of vacuum hood
  3. Use of respirator

Wet Drilling:

Modern drilling machines Harry arrangement by which water could be used to wet and remove the cutting from the drilled hole. This prevents dust from flying to a considerable extend

Use of Vacuum Hood:

A hood is fitted around the drill steel at the rock face which is connected to exhaust pipe through which drilled rock dust is sucked and removed safely out of the tunnel

Vacuum hood
Vacuum Hood 

Use of Respirator:

Well designed respirators worn by miners offer the best and most up to date protection against dust inhalation. It is a method which is becoming increasingly popular in modern tunnel practice
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