Railway Tunnelling: Lighting, Drainage, Shaft of Tunnels

Lighting of Tunnels

It is very important to ensure that the tunnels are well lit so that the various activities and operations involved in tunnelling can be carried out effectively and safely. The common types of lighting equipment normally used in tunnels are electric lights, coal gas or acetylene gas lights, or lanterns. Electric lights are considered the best option, as these radiate bright light of the required intensity, are free from smoke, are easily manoeuvrable from the point of view of extension, etc.

Places where plenty of light should normally be provided are operation points, equipment stations, bottom of shafts, storage points, tempering stations, underground repair shops, etc.

Drainage of Tunnels

Good drainage of the tunnels is very essential in order for them to operate safely and smoothly during the construction period as well as afterwards. The sources of water for this purpose include ground water and water collected from the washing of bore holes. Water seeping in up through the ground as well as from the washing of bore holes is collected in sump wells and pumped out. If the tunnel is long, a number of sump wells are provided for the collection of water.

After the construction is over, drainage ditches are provided along the length of the portion of the tunnel that slop from the portal towards the sump well and are used for pumping the water out.

Shaft of Tunnels

Shafts (Fig. 30.11) are vertical wells or passages constructed along the alignment of a tunnel at one or more points between the two entrances. A shaft is provided for the reasons listed below.

Working shafts These are provided for the expeditious construction of tunnels by tackling the same at a number of points. These are generally vertical and of a minimum size of 3.7 m × 3.7 m or of a diameter of 4.30 m.

Ventilation purposes In order to ensure better ventilation, these shafts are generally inclined and have a girder size of about 1.2 m diameter.