How safe is Zojila Tunnel? From escape tunnels to SCADA systems - know more

The breakthrough of the Zojila Tunnel marks a major milestone for one of India's most complex infrastructure projects. Stretching 14.15 km beneath the Himalayas and located at an altitude of more than 11,500 feet, the tunnel is being built through a region known for extreme weather, avalanches, and constantly changing rock formations. Engineers have relied on multiple layers of safety systems, both during construction and for future operations, to minimise risks.

The tunnel, which connects Baltal in Kashmir with Minamarg in Ladakh, will bypass the avalanche-prone Zojila Pass and reduce travel time from more than three hours to about 15-20 minutes, providing year-round connectivity.

READ MORE: Zojila tunnel breakthrough: The project that could change travel to Ladakh forever

Excavating an 'alive' mountain

Building a tunnel through the Himalayas presents challenges that are very different from those encountered in other parts of the country. Temperatures can fall to minus 30°C, while the terrain is prone to avalanches and geological surprises.

Arnold Dix, geologist, engineer, and former president of the International Tunnelling and Underground Space Association, said working in such conditions is demanding for both workers and machinery.

The Himalayas are also geologically young and highly active. Describing the mountain range, Dix said: “To a geologist, the Himalayas are ocean floors that have been pushed upwards.”

According to him, the rock conditions can change dramatically within short distances. Engineers may encounter soft rock, boulders, cracks, cavities and heavy water ingress, requiring different treatment methods to maintain stability.

Dix described the mountain range as “alive,” moving and responding to pressures it feels.

“The tunnel cannot hold the mountain up, simply because it is too big. The only way to tunnel through a mountain then is to do it in a way that upsets the tunnel the least, and ensure the weight falls onto the wayside. It is like conducting an operation without anaesthesia. This is why tunnelling in the Himalayas has to be done slowly and carefully,” said Dix.

New Austrian Tunnelling Method used

To deal with these conditions, engineers adopted the New Austrian Tunnelling Method (NATM), which is considered suitable for difficult geological terrain.

The method involves selective blasting, followed by reinforcement using shotcrete, or sprayed concrete, and rock bolts to stabilise the surrounding rock. Excavation is carried out in two stages, with the upper half of the tunnel being dug first and the lower section later.

The design also allows engineers to adapt to changing rock conditions. Depending on the amount of water entering the tunnel, drainage pipes are installed to gradually release water and prevent pressure build-up that could lead to flooding or collapse.

Similarly, the number, size and spacing of rock bolts are adjusted according to the cracks encountered. In some cases, the tunnel alignment itself can be modified to avoid weak sections of the mountain.

Multiple evacuation and rescue systems

Safety measures extend beyond construction. The 14.15-km tunnel incorporates an independent parallel egress tunnel that will serve as an escape route in emergencies.

Cross-passages at regular intervals connect the main tunnel with the escape tunnel, allowing people to quickly move away from smoke or fire and reach a protected, breathable environment.

Three vertical ventilation shafts have also been built across the length of the tunnel to ensure a constant supply of fresh air and facilitate rescue operations when required.

The first shaft, which is also India's deepest, extends 474.3 metres below the surface. The second shaft is 367.5 metres deep, while the third reaches 213.5 metres.

These shafts help remove smoke and toxic gases during emergencies while creating access points for rescue teams.

Smart monitoring system

The tunnel is also equipped with an advanced Supervisory Control and Data Acquisition (SCADA) system for round-the-clock monitoring and traffic management.

The system integrates 24x7 CCTV surveillance, radio communication controls, emergency lighting, and variable message signs, enabling operators to manage incidents and direct traffic efficiently.

Together, the escape tunnel, ventilation shafts, cross-passages, and smart monitoring infrastructure are expected to make the Zojila Tunnel not only India's longest road tunnel but also one of its most safety-focused infrastructure projects.