NGRI flags stress zones in SLBC tunnel

Hyderabad: The National Geophysical Research Institute (NGRI) has submitted a detailed survey report on the structural integrity and subsurface conditions of the Srisailam left bank canal (SLBC) to irrigation minister N Uttam Kumar Reddy, marking a crucial step in ensuring safety of ongoing tunnel works.The report, handed over by NGRI chief scientist HVS Satyanarayana during a review meeting on Friday, draws on advanced geophysical techniques such as seismic imaging and electrical resistivity tomography. These methods helped detect stress zones, seepage patterns, and tunnel roof stability issues that conventional inspections could not identify. The findings also explained factors behind the Feb 22, 2025, roof collapse. Minister Uttam underlined the govt's commitment to worker safety, saying scientific inputs from NGRI would guide decisions on tunnel completion. He praised the institute's work and sought its involvement in soil investigations at the Medigadda, Annaram, and Sundilla barrages of the Kaleshwaram lift irrigation project, where rehabilitation is planned. "The report will be thoroughly examined, and necessary measures will be initiated based on its recommendations," he said. The minister directed irrigation officials to fast track SLBC tunnel works by mobilising equipment from domestic agencies alongside machinery being procured overseas. Progress so far stands at 151.5 metres, with imported electric loaders and heavy dumpers recently added to the fleet. Officials expect excavation to accelerate, targeting 200 metres per month from each side. The BIS-backed geophysical survey is seen as critical to curb further accidents and ensure completion of project.