What Has The Learning Curve Been From The Silkyara Tunnel Cave-in?

The Silkyara tunnel collapse in Uttarkashi exposed the flaws in tunnel construction safety. It cast a shadow on the ambitious project, raising questions about safety protocols, construction practices, and the environmental impact in the fragile Himalayan region
By Rashme Sehgal
  • In February 2018, the Cabinet approved a 4.5 km tunnel to cut travel time from Uttarkashi to Yamunotri by 26 km
  • With a tunnel collapse alarm, lacking protocols, a JCB was the sole tool; an Auger Drilling Machine from Haridwar was ordered
  • Global experts from Thailand and Australia aided rescue efforts; multiple government agencies joined forces to support the operations

Nationwide geologists highlighted neglect of Himalayan tunnel construction principles in the Silkyara tunnel; fundamental tenets were disregarded

THE Silkyara-Balkot tunnel is part of the highly prestigious Char Dham project connecting the four religious sites of Kedarnath, Badrinath, Yamunotri and Gangotri with an all-weather four-lane road. The green signal for the construction of this 4.5-kilometre-long tunnel was given in February 2018 when the Cabinet Committee on Economic Affairs, with Prime Minister Narendra Modi as its chair, gave the approval for its construction. The implementation work was given to the National Highways and Infrastructure Development Corporation Limited (NHIDCL), which in turn engaged the Hyderabad-based Navayuga Engineering Company Limited for construction.

The tunnel was expected to help reduce travel time from Uttarkashi to Yamunotri by 26 kilometres. In June 2018, NHIDCL signed a contract for Rs 853.79 crore with Hyderabad-based Navayuga Engineering Company Limited for engineering, procurement and construction of the Barkot-Silkyara tunnel.

Being a high-profile project, the Ministry of Road Transport was pushing for an early completion of the project. Their hopes of an early completion were belied when on November 12, a section of this tunnel collapsed. This happened around 5.30 am on the day of Diwali, considered one of the most auspicious festivals of India.


The workers confirmed after their evacuation that on the morning of November 12, they were busy at work, when debris began falling around them and they could hear the mountain rumble. Since this happened frequently, they did not pay attention to it for almost thirty minutes or so till they realised that their exit route had been blocked and they could not escape.

They had chosen to start work early so that they could celebrate the Diwali festival with their family and friends later that day. The more cautious of their colleagues had chosen to move out of the tunnel little realising that a large section of rubble and stone would cave-in leaving their colleagues trapped inside.

Once the alarm of a major tunnel collapse was sounded, the rescue protocols are supposed to become operational. Sadly, for such a major infrastructure project, there were few protocols in place. Bhim Singh Rawat, a scientist working with the NGO South Asia Dam Rivers and People pointed out, ‘No safety protocols were in place. When the State Disaster Response Force team arrived at the tunnel site all they found was one JCB. An Auger Drilling Machine (a specialised tool to create horizontal bores or underground tunnels without disturbing the surface) was ordered from Haridwar to dig a hole through the rubble. It arrived on November 14, a full 48 hours after the accident had occurred.’


By then experts from the National Disaster Response Force (NDRF) and the local police had also arrived at the spot. The collapsed section was 270 metres from the mouth of the Silkyara tunnel. Their immediate objective was to cut through the debris in order to place 900 mm mild steel pipes for the workers to crawl out. But this machine broke down and was not able to cut through the rock and so a more sophisticated state-of-the-art American-made auger machine with horizontal dry drilling equipment attached to it was sent for from Hyderabad.

Excessive road and rail tunnel building has triggered a huge increase in landslides in the Himalayas, and is a contributing mechanism to the increasing number of tunnel cave-ins and other disasters in the ecologically fragile Himalayas

Fortunately for the workers, a four-inch diameter pipe had been inserted soon after the accident and was being used to supply them with oxygen and some dry fruits and snacks. Since water was already dripping in the tunnel, this was used as a source of drinking water. The workers had two other advantages. Their electricity supply was in place. They also had practically 1.5 kilometres of legroom to move around in.

The American auger was flown in by two special Hercules IAF airplanes landing on a specially created airfield near the tunnel. Rescue operations continued to be hampered by frequent landslides and the specially constructed platform on which the American auger was to be placed had to be reconstructed again since it got damaged by a landslide.

International experts were brought in from Thailand and Australia to assist in the rescue operations and a slew of government agencies were also roped in to assist in the operations. These included the Indian army, the IAF, NHIDCL, ONGC, DRDO, BRO, Rail Vikas Nigam, National Disaster Response Force, State Disaster Response Force Authority, Satluj Jal Vidyut Nigam, Tehri Hydro Development Corporation(THDC), ISRO, Geological Survey of India and several private agencies including the Trenchless Engineering Private Ltd and L&T’s Safety Unit. From the start, the PMO was acting as the nodal coordinating unit to oversee this expensive rescue mission.

The early confidence that this would prove to be an easy task soon gave way to the realisation that things were going to prove much trickier than anticipated. For one, on November 16, the American auger machine also got damaged after encountering some hard rock. Repair work was not easy and when the horizontal drilling did start from the Silkyara side, 800 mm pipes were drilled into the 900 mm steel pipes in order to give it additional support.


It was a race against time. The question on everyone’s mind was how long would this rescue mission take. From the start, the NHIDCL director Anshu Manish Khalkho refused to commit himself to any timeline. Realising that not one approach would work, plans were chalked out to adopt a ‘five-pronged approach’. The first prong was to use the augur machine to drill a hole from the Silkyara side. The second thrust would be to use the THDC to initiate drilling operations from the Barkot end. Using the drill and blast method, they succeeded in excavating a 6.5-metre-long drift.

The third thrust to be executed by the SJVN Ltd was to go in for vertical drilling from the hillock above the tunnel and a drilling machine was sent for with experts from ONGC being requisitioned to help in this process. To be on the safe side, micro-drilling through the tunnel’s left side was also operationalised. With the tunnel being approached from so many ends, experts warned of the possibility of yet another cave-in.

Being a high-profile event, more and more VIPs began camping outside the Silkyara tunnel. Each VIP gave their own assessment of the situation and what they believed would be the timeline for the rescue. Union Minister of Road Transport and Highways Nitin Gadkari arrived there five days after the cave-in. After making an on-the-spot assessment, he believed rescue operations would be mopped up within two to three days. Gen VK Singh (retd) MOS, Road Transport and Highways, reiterated a similar date line while Prime Minister’s former advisor Bhaskar Khulbe told the media he expected rescue operations to be wrapped up within ‘five to six to seven days’. Australian tunnelling expert Professor Arnold Dix insisted rescue operations could go on till Christmas.

Relatives of some of the workers trapped inside had arrived from different parts of the country. Tempers began to rise at the frequent delays. A couple of impromptu demonstrations and slogan shouting were held outside the mouth of the Silkyara tunnel which was now buzzing with media hounds and top-notch politicians and bureaucrats. Workers who were part of the construction team were also spilling the beans on what the working conditions had been like inside the tunnel given that this tunnel had seen several cave-ins earlier. Khalkho spilled the beans and admitted to over 21 cave-ins in the past. A major tunnel collapse had taken place in 2019. Fortunately, no workers were trapped in that accident.

Railways chief engineer Alok Verma who has supervised the construction of several tunnels was amazed by Khalkho’s disclosure. ‘A claim of this nature, if true, calls for explanations. First and foremost, did a thorough survey and study of the rock formations along the alignment precede the selection of the tunnel alignment? The collapse of a 60-meter portion of a tunnel is an uncommon occurrence. If the roof has not been reinforced with steel and concrete at the tunnel’s excavation face, it might collapse; however, a collapsed tunnel where this reinforcement has been finished is a serious mishap. Furthermore, given the frequency of collapses in the tunnel’s completed section, why was the tunnel’s location not altered following a comprehensive geological and geotechnical investigation?’ he asks.


With so many cave-ins, the all-important question was why were no safety ducts in place given that the engineers constructing the tunnel knew they were working along a fault line. Fellow workers and their family members were also asking why the Silkyara tunnel had no escape route. Especially since the government sanction of this tunnel project in February 2018 had stated it would include an “escape passage’. Why had no government agency ensured an escape passage be put in place and how was the Navayuga Engineering Company permitted such an oversight?

With the rescue operations having become the cynosure of all eyes, leading geologists from across the country began pointing out that the fundamental tenets of tunnel building in the Himalayas were not followed in this Silkyara tunnel construction.

Tunnel construction, Dr PC Nawani, former director of the Geological Survey of India stressed, needed inputs from an expert team of engineering geologists whereas construction in the Char Dham project had been handed over to contractors who were using all kinds of shortcuts with little knowledge of the existing terrain.

A multitude of government agencies joined forces in the rescue operation. The collaborative effort involved the Indian army, IAF, NHIDCL, ONGC, DRDO, BRO, Rail Vikas Nigam, National Disaster Response Force, State Disaster Response Force Authority, Satluj Jal Vidyut Nigam, Tehri Hydro Development Corporation, ISRO, Geological Survey of India, and private entities like Trenchless Engineering Private Ltd and L&T’s Safety Unit. From the start, the PMO was acting as the nodal coordinating unit to oversee this expensive rescue mission

CP Rajendran, geologist and adjunct professor at the National Institute of Advanced Studies, has been raising the red flag for the last five years against the rampant construction work going on in the Himalayas.

Rajendran had pointed out that tectonic fault lines should have been taken into consideration before construction started at the Silkyara–Barkot tunnel especially since the MCT (Main Central Thrust) tectonic fault line along the Himalayas poses a grave danger to the construction of roads and tunnels. Why on earth was the Silkyara tunnel located close to this fault line?

Rajendran was equally horrified by the fact that ‘No Standard Operating Procedures were being followed in Silkyara with serious consequences. Previously such excavations in the mountains were carried out under the constant supervision of competent geologists, followed by continuous tunnel logging among other precautionary measures. The question is why no safety norms or the reviewing had been ordered by the authorities even after a tunnel collapse from the same area happened in 2019?’

Varun Adkhikari, an engineering geologist wrote in his blog that ‘the collapse at Silkyara is indicative of a classic case of unprofessional tunnelling practices and negligence toward essential tunnelling principles. It also highlights the importance of maintaining diligence in adhering to proper procedures, especially in reprofiling and utilizing hydraulic breakers or minor blasting with due consideration of the tunnel’s specific conditions and potential consequences on the surrounding rock mass.’

Navayuga Engineering Company hired the services of Bernard Gruppe, a German-Austrian engineering services company working on tunnel design and construction. Following the tunnel cave- in, they issued a statement that “the geological conditions have proved to be more challenging than predicted in the tender documents”.

Amidst all this cacophony, nearly a fortnight had passed with the rescue operation continuing to be dogged by frequent vicissitudes. After drilling up to 46.8 meters through the debris, the auger machine got stuck again in the rubble, and a sigh of despondency broke out. There were just 10-12 metres of the collapsed portion of the tunnel to go to and yet they were being dogged by one breakdown after another. Officials then decided to get a team of six rat miners using primitive equipment to drill the final portion. While one rat miner dug the debris, the second collected it and a third carried it out.

Twenty-four hours later, on the seventeenth evening after the cave-in, a Tuesday, the rescue efforts were successful and all the workers were retrieved from the tunnel. They were wheeled out by the rescuers on stretchers through a 90 cm( 3 feet) wide steel pipe after having spent 400 hours locked inside the tunnel.


But questions remain about the whole operation. No FIR has been lodged against the Navayuga Engineering Company for criminal negligence. When the VIPs present at the accident site were asked this question, they sidestepped it insisting their focus for the present was to ensure the workers were rescued safe and sound.

With so many cave-ins, the all-important question was why were no safety ducts in place given that the engineers constructing the tunnel knew they were working along a fault line. Fellow workers and their family members were also asking why the Silkyara tunnel had no escape route

The Uttarakhand state government led by CM Pushkar Singh Dhami did issue a statement that a reassessment of all the tunnels under the Char Dham project will take place in the next six months. But unless top geologists are roped in, such a reassessment will serve little purpose.

Excessive road and rail tunnel building is one of the most alarming aspects of this excessive construction activity going on in the Himalayas which has triggered a huge increase in landslides. A graph prepared by scientists showed landslides have increased by 2900 percent in Uttarakhand in the last five years. Landslides do not occur in isolation. Depending on the nature of rocks, their competency, and the blasting methods employed, road and dam constructions act as contributing triggering mechanisms.


Why has India been witnessing an increasing number of tunnel cave-ins and other disasters in the ecologically fragile Himalayas? What steps need to be immediately taken in order to ensure such a nightmare does not recur?

Anjal Prakash, research director at the Bharti Institute of Public Policy summed up the mood when he warned that our present policies were “playing havoc with the Himalayas. Such disasters are going to rise because we are living in a fragile ecosystem. We need to re-look at all the projects we are executing in the Himalayas. Each of them needs to be re-evaluated keeping safety aspects in mind.”
Raghav Chandra, former chairman of the National Highways Authority of India (NHAI), the nodal body executing the Char Dham Yojana stressed the need to find a balance between “development aspirations and environment protection.”
Consultants being hired by the government were clearly not doing due diligence. “The consultants are cutting corners while preparing DPRs (Detailed Project Reports). Proper technical evaluations are not being prepared and, as a result, the execution is slipshod,” he said.

Minister of Roads and Surface Transport, Nitin Gadkari had tweeted recently on this same subject criticising the quality of DPRs being prepared for road projects. Speaking at the Indian Road Congress at Gandhinagar he said, ‘DPR makers…. What words should I use for them? I have never seen people doing such shoddy (ghatiya) quality ( of work)… tell them ( the DPR makers) exactly what I said… they sit at home, look at Google and make DPRS.. Accidents are happening,’ He added, ‘The important thing is making a 101 percent perfect DPR without compromising on design and quality. Is this a good thing that there are five lakh accidents in the country and 1.5 lakh deaths (every year) ?’

Heading such a key ministry, the question to ask Gadkari and his huge team of technocrats and bureaucrats is why aren’t they reviewing the content of a DPR before starting work on a project. Surely a ministry such as his has the expertise to evaluate the DPRs before a project gets executed.

Most environmentalists believe the root of these Himalayan disasters is politicians handing out contracts running into thousands of crores to construction agencies that are seen to be close to them.

Hemant Dhyani, a former member of the expert committee appointed by the Supreme Court to look into this entire Char Dham Yojana fiasco, emphasised repeatedly that their suggestion to construct a narrower tunnel was disregarded, resulting in heightened blasting activities and an elevated risk of collapse. Environmental risk assessments were neglected, with tunnels being exempted due to the project’s segmentation into sections of less than 100 km each. “This is a serious wake-up call for all of us,” he said.

In the light of this disaster, the government must immediately stop the entire road widening activities related to Char Dham project including tunnelling work along various parts of its stretch until a thorough scientific review of this project by independent experts is conducted.

No safety audit on the cave-in has been placed so far in the public domain. Work on the tunnel construction has restarted, this time from the Barkot end. A great deal of water has accumulated inside the tunnel which experts believe is not a good sign. But till such time as the enquiry report is not made public, finding out the reasons for so much water logging and for frequent cave-ins is akin to shooting in the dark.

Rashme Sehgal

Rashme sehgal began her career as a poet-cum-short story writer in 1970s. she then shifted to journalism and worked with several leading newspapers including The independent, The Telegraph and The Times of india

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