Tunnel construction technologies
Tunnel - horizontal or inclined artificial underground construction used for transport, water passages, communication set-down or manufacturing enterprises.
From the point of intended purpose tunnel can be divided into 7 groups:
- Railway tunnels
- Traffic tunnels
- Subway tunnels
- Hydraulic tunnels
- Communication tunnels
- Mining tunnels
- Special tunnels
From the point of location the tunnels can be divided into three groups:
- mountain tunnels (headed in mountainous area through ridges, dividing ranges and uplands);
- underwater tunnels (tunnels constructed under river beds or other water lines) for providing the way for transport and allocation of engineering communications;
- Flat or city tunnels (e.g. subway tunnels)
Laying depth of tunnel, its length, location and cross-section depend on the appropriation, topographic, geological and climate conditions. Longitudinal section of tunnel can be single- and double-leaning (with leaning to the both sides of the tunnel).
Tunneling is one of the most complex kinds of construction works. Tunneling is performed on two similar restricted in length sections - çàõîäêè. Section length - depth of round - depends on geotechnical conditions of tunnel heading, cross-section, width, heading method, formwork materials. When tunneling is performed in rock and half-rock ground, depth of round defined by degree of stability of excavation ground outline is 2-4 metres.
Tunneling works are organized by means of flow-line conveyer method and are performed cyclically. Tunnel construction process is divided according to kinds of works. The principle of flow-line conveyer method is that work on every section is performed after leading face with permanent speed.
In this case all tunnel construction works are united construction flow, providing completed tunnel constructing with the speed of leading face construction. Maximum possible heading speed depends on the equipment and can vary in every working zone.
The second principle of tunnel works is cyclic recurrence of performance. Cycle is an isochronous completed process of definite volume of works performing. There must be integer number of cycles per day in order to organize brigades' work in a better way and increase product liability.