Like an umbrella in the pouring rain, bunkers protect soldiers in remote, desolate landscapes. Recently, IIT-H and Simpliforge Creations, in collaboration with the Indian Army, constructed the world’s highest in-situ 3D-printed bunker at 11,000 feet in Leh, under Project PRABAL. This is not only a global first for high-altitude in-situ 3D construction but also showcases the power of academic–industry synergy in overcoming the extreme challenges of the Himalayan terrain. With specialised materials, rugged robotics, and a mission-driven resolve, the project — led by Professor KVL Subramaniam from IIT-H , Simpliforge CEO Dhruv Gandhi, and Army liaison Arun Krishnan (also a PhD student at IIT-H) — demonstrates how cutting-edge Indian deep tech is redefining the future of rapidly deployable military infrastructure. In an exclusive conversation with CE, Prof Subramaniam offers insights into the project.
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Please explain the 3D bunker your team has built. How long have you been working on this project?
We started working on this project about a year ago. Concrete 3D printing is relatively new. It’s essentially an extension of what we call additive manufacturing, but applied to civil engineering. So, instead of printing small models with plastic or metal, here, we’re printing entire buildings with concrete, layer by layer.
The idea is to use a digital blueprint — something modelled on a computer — and have the printer build it layer by layer. This method gives us speed, efficiency, and precision. You place the material only where it’s needed, so there’s minimal waste. More importantly, it opens the possibility of remote construction — building in places where it’s hard for humans to work.
At IIT-H, we developed the right material, the structural design, and the complete system that enables us to print a structure on-site with minimal human intervention. That was the real challenge: moving from printing small lab samples to full-scale field structures. This bunker was our attempt to demonstrate that capability.
The project was a collaboration with Simpliforge Creations, a startup that developed the printer, software, and control systems. We printed the bunker in Leh, a high-altitude, remote location, in collaboration with the Indian Army. The goal was to show how 3D printing could be used to build military-grade infrastructure.
In the current climate of tension, how can technology like this help?
Every bit counts. This isn’t offensive technology — it’s protective. Better bunkers mean greater safety and confidence for our soldiers. If they know the structure around them is robust and engineered for that environment, it provides a psychological edge as well.
You mentioned that concrete 3D printing gained prominence around six or seven years ago. Was that a global phenomenon or something that emerged specifically in India?
Additive manufacturing has been around for two decades — especially for plastics and metals. Small 3D printers for prototypes have existed for quite a while. But printing with concrete at building scale only started gaining traction in the last 10 years.
As for India, I’d say we’re actually doing quite well — on par with, or even ahead of, some countries. We have startups and research institutions pushing boundaries. At IIT-H, we’ve developed our own printers, control algorithms, and custom materials. So, while the technology globally is about a decade old, we’ve caught up quickly and are even leading in certain areas.
For example, two years ago, we worked with Simpliforge to print a 7.5-metre-long bridge on our campus — one of the first of its kind in the world. Beyond homes, we’re now exploring protective structures, transport infrastructure, and even extraterrestrial construction. The vision is to eventually send a 3D printer and control system to the Moon or Mars. Instead of deploying labour, we’d send a printer that could autonomously build shelters using available materials. Of course, that’s still a way off, but the foundational technology is already being developed. Remote construction is where this tech really shines.
Could you elaborate on the special concrete mix used in 3D printing?
Certainly. Standard concrete isn’t suitable for printing — it’s not pumpable and doesn’t retain its shape. For 3D printing, the material needs to flow through a nozzle yet hold its shape upon placement. It’s a delicate balance.
We reduce aggregate size and use rheology modifiers — chemical additives that control flow and behaviour under pressure. There’s a lot of science behind particle packing and balancing properties.
Printing in Leh brought extra challenges. The climate is extremely dry, with about 20% relative humidity, and oxygen levels are around 50% of those at sea level. Water evaporates quickly, concrete cracks easily, and machinery doesn’t perform efficiently.
We had to engineer the mix to retain moisture longer and reduce the strain on the pump and generator. If the material is too stiff, it causes the pump or generator to trip. So, we had to formulate a mix that prints smoothly while withstanding such extreme conditions.
What were the biggest or most unexpected technical issues during the print?
There were many, but logistics was the biggest surprise. There was no road to the site. We had to transport everything — be it the printer or materials — using 4x4 vehicles. Then came the difficulty of finding a flat surface suitable for levelling and installing the printer. In mountainous terrain, that’s not easy.
Another major issue was the environment. Even though we knew oxygen levels were low, experiencing it firsthand was different. You feel exhausted just walking. It takes around three days to acclimatise.
The generator’s output was far lower than expected. Unable to run the mixer, pump, and printer simultaneously, we had to stagger operations. Everything had to be scheduled to avoid overloading the generator.
Is this a single-room structure? Could it be scaled into an underground bunker?
Yes, this is a single-room structure. But we’re already working with the Army on underground and multi-room designs. In fact, we’ve printed a 1,800-sqft medical facility at Jhansi cantonment. It is a multi-room structure.
This technology is scalable. The real strength of 3D printing lies in its ability to deploy infrastructure rapidly without a large workforce. That’s vital in remote or high-altitude zones where manpower is limited and time is critical.
Since this is military-grade infrastructure in a sensitive zone, were there special security or logistical protocols?
Absolutely. The Army was incredibly supportive and collaborated closely with us. This was an NCNC (No Cost No Commitment) trial, meaning the Army provided operational support without financial involvement.
This experience gave us deeper appreciation for the conditions the Army faces. Some of their bases are even higher than ours. The goal is to eventually transfer this technology so they can operate it independently — just like any other equipment.
We’re also exploring use cases on the western front — hot, arid desert zones. There, we aim to print structures offering thermal comfort. One concept is to use multi-wall construction to keep interiors cool, even when it’s 50°C outside.
If India were to scale a network of 3D-printed structures in remote, high-altitude zones, what would be the biggest challenges?
The biggest bottlenecks are:
Manpower: Acclimatisation delays and fatigue.
Machines: Need for modular, rugged printers that function in extreme conditions.
Materials: Using local resources while ensuring performance and quality.
Ideally, we’d like to mount the printer on an all-terrain vehicle — something akin to a tank — so it can be driven to any location and print directly on site. That’s the vision: autonomous, mobile construction systems.