Helicopter borne magnetic survey begins at SLBC tunnel site
HYDERABAD: As part of efforts to restart excavation of the Srisailam Left Bank Canal (SLBC) tunnel, a helicopter-borne magnetic geophysical survey will begin today. The Directorate General of Civil Aviation (DGCA) has given its approval for the operation.
CM, irrigation minister to oversee operation at Mannevaripalli
Chief Minister A Revanth Reddy and Irrigation Minister N Uttam Kumar Reddy will travel to Mannevaripalli in Nagarkurnool district to oversee the launch of the survey. They will accompany a parallel helicopter flight monitoring the survey process.
The National Geophysical Research Institute (NGRI) will conduct the survey over a 200-km stretch, mapping geological conditions up to 800–1,000 metres below the surface. The exercise aims to identify subsurface features before resuming tunnelling operations.
In February, a portion of the Saranga tunnel collapsed, killing workers and damaging a Tunnel Boring Machine (TBM). Following this, an expert panel recommended conducting a detailed geophysical survey before resuming work to ensure safety.
The SLBC project involves constructing two parallel tunnels. The second tunnel has been completed. Of the 43.93 km first tunnel, excavation of 13.94 km from the inlet and 20.4 km from the outlet side has been finished, leaving 9.8 km in between. Once completed, it will be one of the longest human made tunnels in the world..
Survey to map underground conditions up to 1 km deep
For the survey, a 24-metre transmitter loop will be suspended from a helicopter and flown over the alignment area. The transmitter will send electromagnetic waves into the ground; their reflections will be captured by receivers to analyse underground structures. Experts will assess whether shear zones or water pockets exist at depths of up to 1 km, helping determine the technology required for safe excavation.
The chief minister’s visit to the Nallamala forest region has drawn attention, especially as he is taking time out from the Jubilee Hills by-election campaign. Revanth Reddy will reach Mannevaripalli at 12.30 pm, meet local leaders from Achampet, and later address the media.
