Underground surveying methods
Generally underground surveying comprises of three survey works:
- Surface Survey
- Transferring the alignment and points underground
- Leveling within tunnel
First the surveying is done at the surface of the location from where tunnel is to be passed underneath. Then the points and alignment are transferred underground using various surveying tools. And once, dug inside, leveling of the tunnel is done within.
Underground surveying embraces the survey operations performed beneath the surface of the earth in connection with tunneling, exploration and construction in subterranean passageways. It is quite different from surveying on the surface. Applications of Underground Surveys:
The major application of underground surveys is in the construction of tunnels and other underground utilities. The tunnel is constructed when open excavation becomes uneconomical usually when it is more than 20 m.
Reduces the grade
Shortens the distance between given points separated by a dividing mountain or ridge.
Meets the demand of-modern rapid transit in a city.
Engineering operations to be performed
Establishment of permanent stations marking the proposed route.
—- Kumar Sanjeev (Extracted from internet)