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In 2018, the Ministry of Road Transport & Highways began construction of a 4.531 km two-lane tunnel at Silkyara, connecting Gangotri and Yamunotri via the Radi pass in Uttarakhand. The Silkyara tunnel, part of the Char Dham project, will offer all-weather connectivity to four Hindu shrines in Uttarakhand, reducing the snow-affected NH-134 road from 25.6 km to 4.531 km.
A Closer Look at the Factors Behind the Incident
A section of the Silkyara tunnel collapsed on November 12, trapping 41 workers for 17 days. The collapse occurred after reprofiling work on November 10 and breaking work on November 12, where the work had been completed. Authorities are investigating a possible link to a landslide in the fragile Himalayan region, with experts highlighting the potential consequences of rapid development. A geological report suggests weaker rocks on the Silkyara side could lead to slip circle failure.
The report on the region’s geology, based on exploratory drilling at Silkyara, Barkot, and Radi Top, has limitations, with only 20% of the rock types being considered “very good,” indicating geological instability. Dr. Naveen Juyal questions the construction methodology.
The Silkyara Tunnel in Uttarkashi has experienced 19–20 minor to medium-level collapses in the past five years, attributed to the region’s geological characteristics. Khalkho reported that workers were trapped in a tunnel collapse, affecting both the Silkyara and Barkot ends, with more collapses on the Barkot side than the Silkyara side.
Khalkho identified a 160-260-meter segment within the tunnel’s mouth from the Silkyara end as a’red zone’ or shear zone’ due to the presence of brittle rocks. Reports reveal the construction plan for an escape tunnel was never built, with expert Arnold Dix acknowledging its absence due to tunneling’s failure to consider geological conditions. The Indian government has clarified that a separation wall was incorporated into the Silkyara bi-directional tunnel on the Dharasu-Yamunotri highway, with egress openings at regular intervals for vehicular crossover and pedestrian cross passage, to serve as an escape route during emergencies.
Dinesh Sati suggests inadequate tunneling practices contributed to the Silkyara tunnel’s failure, citing a shear contact between the underlying shales and metabasics sequence. Sati’s preliminary geology and geotechnical feasibility investigations revealed that tunnels aligned in such a manner are susceptible to failure, possibly due to reckless retrofitting during lining work.
Call for Enhanced Safety Measures
The National Highways Authority of India (NHAI) plans to conduct a safety audit of all 29 under-construction tunnels across India following the collapse of a tunnel. MoRTH has formed a five-member expert panel to investigate the Silkyara tunnel collapse, recommend changes to standard procedures, and propose safety measures within 45 days.
The expert team will conduct an on-site inspection, review project records, scrutinize detailed project reports and design reports, assess geological mapping, conduct geotechnical investigations, and study site conditions. They will also evaluate the project implementation system. Dr. Manoj Verman highlights the Silkyara tunnel collapse as a reminder of the risks of tunneling through challenging Himalayan terrain.
Tunneling through mountains requires rigorous preparedness and vigilance throughout the project. However, safety measures and oversight gaps are evident at every stage, highlighting the need to address these issues to prevent engineering marvels from causing human suffering.
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