Mumbai University > Civil Engineering > Sem 8 > Construction Engineering

Marks: 5Marks

The term lining is used to indicate the finishing touch given to the cross section of tunnel.If the tunnel is passing through hard stratum, it may be left unlined.Lining may be of two types:

Temporary lining:

it is provided for supporting the roof and the walls of tunnel during construction.

Permanent lining:

it is provided in soft soil which is always liable to disintegrate.The ideal lining should be easy to maintain, economical, durable, simple to construct and stable.

The basic materials for tunnel lining construction are cast-in-place concrete, cast-in-place and prefabricated reinforced concrete, cast iron and steel. These materials are chosen according to conditions of construction area and tunnelling methods. The shape and size of lining are defined by size, depth and function of the tunnel and sort of take up load (rock pressure, hydrostatical pressure, traffic load, etc).Cast-in-place lining is mainly used for construction of tunnels with most complex structure and big cross-section. Precast lining is widely used for shield and erector- arm tunnelling, mainly in subway tunnels.