Underground 3D Scanning in Bhutan

Surveying cavities in underground excavation projects can be difficult and dangerous. The collapse of a roof inside the main access tunnel at a hydroelectric dam construction site in Bhutan resulted in a loss of life and a significant delay in progress. Project participants could not move forward with the tunnel work until they could ascertain the size and condition of the cavity that remained above the caved-in debris blocking the chamber. This article describes how an Indian technology application company deployed a laser scanner specially designed for cavity measurement to accurately determine the volume and dimension of the inaccessible space.

In 2008, the governments of Bhutan and India committed to working jointly on the development of a multi-billion-dollar hydroelectric project in Bhutan’s Punatsangchhu region, along the river of the same name. With an original completion date of 2020, the entire endeavour would generate 10,000MW of power and supply electricity to millions of homes in Bhutan and India.

The two governments set up the PHPA, an autonomous body involving organisations from both countries, to work on the massive undertaking. The centerpiece of the second phase of the project (called Punatsangchhu-II or ‘PHPA-II’) would be a dam of 86 metres high and 213.5 metres wide at the top. A series of tunnels, desilting chambers, surge and pressure shafts and an underground power station would be constructed, extending several kilometres from the dam site

The two governments set up the PHPA, an autonomous body involving organisations from both countries, to work on the massive undertaking. The centrepiece of the second phase of the project (called Punatsangchhu-II or ‘PHPA-II’) would be a dam of 86 metres high and 213.5 metres wide at the top. A series of tunnels, desilting chambers, surge and pressure shafts and an underground power station would be constructed, extending several kilometres from the dam site.