Tunnels are very important structures which are being used in various construction like in road, railway for defense
purpose and laying of pipelines
... [Show More] etc. Tunnels have different shapes based on their uses and the ground conditions and the availability
of materials. All tunnels have various degrees of complexity depending on function and safety needs or the code requirements at
the time of construction, but most tunnels employ one or many functional systems, such as lighting, ventilation, drainage, fire
detectors and alarms, fire suppression, communications, and traffic control. With the limited access and confined conditions within
a tunnel; the operation, maintenance and inspection of a tunnel must be thoroughly regimented to provide an adequate level of
safety for the traveling public. Construction of different types of tunnels include some very basic operations or steps which are to
be followed in sequence in order to build or to construct a tunnel. These are known as basic tunneling operations. This tunneling
operations may differ in comparison to older times and this modern time. This paper provides information on Underwater Tunnels
and various tunneling operations involved to make Underwater Tunnel and also provide information related to old methods of
tunneling and new methods of tunneling using ultramodern technology. Some case studies are also there related to the modern
technology which are used on Underwater Tunnel construction. Many Underwater Tunnel structures have been experiencing water
leakages worldwide. Tunnel structures experiencing water leakages are not only old, but also new in some case. The Concrete
Tunnels structures located underwater are generally protected by waterproof membranes as the first defense to prevent water
leakages and rebar corrosion. However, once water leakage occurs, the corrosion mechanism is quite different from other concrete
structures which are exposed to marine or de-icing salt environments. [Show Less]