Latest update on the Zoji La tunnel. See also ^^^
A video posted by the Tribune newspaper which is a day old, states as per MEIL (prime contractors for the tunnel) project managers interviewed for the video that now 700-750m is left for breakthrough for the 13.1 km tunnel. Tunneling is being carried out from both the Baithal/Kashmir end and Minamarg/Kargil end. Tunneling of 6km+ has been completed from the Baithal end and even tunnel lining started and completed for about 3km from this end. Tunneling is active now from the Kargil end for the final breakthrough expected in late April or early May as per the people interviewed in the video from MEIL.
My gyaan: Tunneling in the unstable geology of the Himalayas of fractured and young rocks is slow, with about 3m per day sometimes considered good progress. Faster tunneling can be undertaken if the contractor is confident that the rock strata can be stabilized soon after excavating and faster mucking out, that is removing the debris after excavation. Principally the contractor must be applying modern methods like NATM(New Austrian tunneling method).
There are three shafts to be also dug for ventilation for the tunnel. As of August 2024 this was the situation, my impression is the shafts may be complete:
The eastern shaft (213m) (Kargil end) was reported as completed, while the central shaft (385m) was partially excavated to 125m, and the western shaft (480m) (Kashmir end) was excavated to 266m.
All approach roads, bridges etc from the Sonamarg/Z Morh tunnel, snow galleries and cut and cover work to the portal of the Zoji La tunnel is complete. All that remains is the main tunnel. Besides a terrorist attack at Sonamarg, the extreme cold temps of -20 Celsius hamper work and it plunges to -30 Celsius at night but work is carried out 24 hours. Curing concrete is also an issue and additives have to be used to make sure the concrete cures properly in this bitter cold and the batching plant has to operate properly to supply the concrete, and transportation in the bitter cold from the batching plant to the pumping site at the tunnel is clearly an issue. At the Se La tunnel in Tawang which was opened a year ago to provide all weather connectivity to Tawang, the dampness in the tunnel under the Se La pass hampered BRO to complete the tunnel in the required time as the concrete would not cure properly.
Also by code in India there has to be an escape tunnel parallel to the main tunnel for all tunnels whose length exceeds 1.5km for road tunnels and 3km for railway tunnels. So Metro tunnels cannot be longer than 3km or it will violate code.
This is the 1994 code that covers all aspects of tunneling in India, lining, lighting, mucking etc etc:
https://www.google.com/url?sa=t&source= ... E_HmDPyErZ
Here is the Tribune video, breakthrough at Zoji La soon in about 9 weeks:(Meil has assured elsewhere and in the video, tunnel will be complete by Feb 2028)
https://www.youtube.com/watch?v=dUN7xM8T27c
Post breakthough and stabilization, lining work has to be completed, lighting, ventilation systems, security systems, CCTV cameras, so cabling for all the electrical systems and fire control systems will have to be installed. Lastly road paving and signage.
Here are the official code numbers for tunneling in India
Safety,, including emergency egress (escape tunnels/cross-passages), is primarily governed by
IS 4756: 1978 (Safety Code for Tunneling Work) and the IS 5878 series (Code of Practice for Construction of Tunnels). These standards dictate requirements for safe evacuation, lighting, ventilation, and emergency, though international standards like NFPA/PIARC are often used for modern fire-safety requirements.
Key codes regarding safety and escape routes:
IS 4756: 1978: Sets the fundamental safety code for tunneling work, including emergency procedures.
IS 5878-2-2 (1971): Covers requirements for ventilation, lighting, and safe passage for underground excavation.
IS 17883: 2022: Provides guidelines for geological exploration for tunnels.
After blasting there is a wait of 2-3 hours to vent out noxious fumes and dust. Post that a thin layer of shotcrete is applied to immediately stabilize the tunnel. Then surveying is done to make sure the tunnel is moving along the desired alignment or if additional blasting is needed. If the alignment is satisfactory, rockbolts which are steel nails 3-6m and 23-50mm in diameter which must be drilled into the stable rock from the tunnel surface stabilize the tunnel further and steel arches are also placed to aid stability in poor rock. The length depends on how weak and fractured the rock is. This process of stabilization is very time consuming and has to be repeated every cycle in the NATM method. Post stabilization a moisture barrier is first applied to the tunnel.
Moisture barriers in tunnels are primarily made from flexible, durable polymeric sheets and coatings designed to withstand high hydrostatic pressure and resist chemicals, aging, and low temperatures. The most common materials include polyvinyl chloride (PVC), high-density polyethylene (HDPE), polypropylene (PP), and ethylene-propylene rubber blends (EPDM). You might have noticed these as yellow sheets and sort of look like the material of inflatable boats. Post putting these moisture barriers, concrete is applied as a liner.