Tunnels are built underground with over burden of massive earth and super structures (e.g. underground metro railways) with moderate overburden of rocks (for transport or hydro tunnel) for pavement near to ground tunnel to transit irrigation water (canals with protection cover type)
Tunnel formwork are designed by the people having site experience of movements of machinery, materials, in adverse terrain conditions (e.g. where loose soil rush all of sudden) and still formworks are standardized to reuse with slight additions and alterations to other site condition. |
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Invert sides and Arch section |
| Generally, tunnels are circular and horse shoe in cross section depending upon their functions and type of the ground through which they are driven. Regardless of shape / cross section, they are usually divided into invert and arch sections for concreting as shown in the section. |
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Kerb Section |
| It is common practice to form and place the curb along both sides of circular and modified horse shoe to provide a base of setting the invert form and runway for the gantry (traveler) wheels. |
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