New standard operating procedures In March for tunnel construction, rescue operations

Tunnel Rescue Mission

The Ministry of Road Transport and Highways of India aims to come out with new Standard Operating Procedures (SOPs) to be followed in the event of a tunnel collapse and to prescribe safety measures during tunnel construction.  Officials aware of the ongoing discussions told Moneycontrol, that the SOPs would be announced in March.

"The government plans to introduce the new SOPs before the start of the next financial year to ensure no slowdown in tunnel projects next year, which are key in improving infrastructure in the hilly states in our country," a senior government official said.

MoRTH, the National Highways Authority of India (NHAI), and the National Highways & Infrastructure Development Corp (NHIDCL) have worked with the Delhi Metro Rail Corporation (DMRC) and Konkan Rail Corporation (KRC), micro tunnelling expert Chris Cooper and the President of the International Tunnelling and Underground Space Association, Arnold Dix, to come up with new SOPs, the officials said.

The steps are a follow-up to the findings of the committee that went into the recent Silkyara tunnel collapse.

The new SOPs will address issues such as identifying the 'shear zone' of a project site before creating the Detailed Project Report (DPR) for a tunnel project, a second government official said.

"Correctly identifying the shear zone is key before the construction of any tunnel project in the Himalayas. The new SOPs mandate that the shear zone be accurately identified in all future tunnelling projects through multiple parties," the second official said.

The first official added that as part of the safety audit of all tunnelling projects in India carried out by the NHAI following the collapse of the Silkyara tunnel, it was identified that finding the shear zone of projects was rushed in many cases.

In geology, shear is the response of a rock to deformation usually by compressive stress and forms particular textures. The process of shearing occurs within brittle, brittle-ductile, and ductile rocks.

Shear zone refers to an area of highly deformed, weak and thinned rocks due to regional stress and such zones require special attention, greater monitoring of ground behaviour and more support to avoid any mishaps.

The second official also said that as part of the new SOPs, the government plans to introduce stricter norms to approve the methodology for carrying out the construction work for upcoming tunnel projects.

"To ensure the safety of workers during the construction phase of a tunnel project, stricter norms will be introduced when approving the methodology for construction," the second official said.

Further, the government plans to make it mandatory for any tunnel project to have adequate sensors and instruments that capture ground behaviour to be present during the construction work, to ensure the necessary precautions during construction.

The government's decision to come out with new SOPs for tunnel construction and rescue operations comes after questions were raised over the ambiguity currently existing in the SOP regarding tunnels, particularly in the case of steeply inclined ones.

Back in November 2023, part of the 4.5-km Silkyara tunnel collapsed, entrapping 41 workers and the government carried out a 17-day rescue operation to save the trapped workers.

The Silkyara tunnel is part of the government’s Char Dham Pariyojana to improve connectivity to four pilgrimage sites in the state located in the Uttarkashi district. It is being constructed by the NHIDCL.

NHAI Member Vishal Chauhan had on November 28 said that once rescue operations are completed the government will carry out an audit of all ongoing tunnel projects and also take lessons from the Silkyara tunnel operations to come out with new SOPs for incidents of tunnel collapse.

"We will take lessons from this too and see how we can improve our SOPs (standard operating procedures) and how we can improve our designs to make these projects safer. Once the operation is completed, these things will happen then," Chauhan had said.

The tunnel guidelines stipulate the provision of steps for rapid evacuation in the event of haulage failure. However, officials say that railways is the only entity mandated to construct escape micro tunnels with stairs, given the presence of rail tracks on the surface. For two-lane tunnels, the SOP lacks clarity on whether steps for quick exit are mandatory.

The preliminary probe report reports on the incident suggested that the Silkyara tunnel did not have an emergency exit and was built through a geological fault.

Findings indicated the collapse may have been caused by a geological fault, known as a "shear zone", a member of the six-member expert committee to probe the cause of the collapse said.

In the upper crust, where rock is brittle, the shear zone takes the form of a fracture called a fault. The methods used to protect weak sections depend on the length and strata of the shear zone. This includes the use of forepoles, rock bolts, steel ribs, or shotcrete to reinforce the zone.

There was also no escape passage, despite government guidelines recommending emergency exits for tunnels longer than 1.5 km.

The report also said that the on-site contractor carried out 're-profiling' work without taking adequate safeguards despite knowing the vulnerabilities of the stretch going by records of cavities (collapses).

The report has also mentioned that the contractor had not got approval for the methodology for carrying out the work from the authority engineer appointed by NHIDCL.

The collapse also highlighted the lack of proper supervision on the part of the NHIDCL officials.

The report also mentioned that on two earlier occasions, there were cavities, indicating that the contractor should have taken more precautions while carrying out work.

It added that NHIDCL should have ensured strict supervision and monitoring of work considering that one of its senior officials had said that the tunnel had encountered 21 small collapses (cavities) before the massive one that resulted in 41 workers getting trapped for 17 days.

The report has also suggested the way forward to avoid such mishaps in the future.

It has recommended the need to set up a tunnel centre for roads and railways, developing a new standard operating procedure (SOP) for tunnel safety and a "geological collaborative framework" on the Gati Shakti platform for better planning and execution of projects, particularly in the Himalayan region.

On-site reports have also revealed that no trench cages or safe tubes were used for the workers working in unprotected parts of a trench. Trench cages serve a crucial role in safeguarding workers from potential cave-ins; however, they are not designed to shore up or provide support to trench walls on their own.

The six-member expert committee includes Shantanu Sarkar, Director of the Uttarakhand State Disaster Management Authority (USDMA), Dehradun; Khaing Shing Lurai, Scientist at the Wadia Institute of Himalayan Geology; Sunil Kumar Yadav, Scientist at the Geological Survey of India; Kaushil Pandit, Senior Scientist at the Central Building Research Institute (CBRI)Roorkee; G D Prasad, Deputy Director of Geology and Mineralogy Department; and Tandrila Sarkar, geologist from USDMA Dehradun.