Uttarakhand tunnel rescue: What is an auger machine, what went wrong, and what’s next?

For the machine to work, it is positioned at the starting point of the bore, usually on the surface. It consists of a drill head with an auger or a drill string attached to it. The auger at the front of the machine rotates and cuts through the soil, rock, or other materials underground. Hydraulic or mechanical systems power this rotation.

As the auger advances, it removes the material from the tunnel, and it is usually flushed out by a drilling fluid or mud pumped through the drill string. This fluid serves to lubricate the drilling process, cool the cutting head, and carry excavated material back to the surface. The machine also has a steering system that allows operators to control the direction and angle of the bore.

Horizontal auger machines often use advanced guidance systems, such as GPS and electronic tracking, to ensure accuracy in direction and depth while drilling underground. Once the machine has bored the desired length, the auger is retrieved, and the tunnel is ready.

Why was it used in this case?

In the Silkyara-Barkot tunnel rescue operation, the initial plan to remove the debris blocking the tunnel exit using heavy excavators did not work.

It was later decided that an auger machine could be a good option because if used properly, it can create a passage through the debris with minimum disturbance to the surface. To keep that passage intact, the rescuers are pushing 900 mm and 800 mm wide mild steel pipes along with the auger blade. Once the passage is complete, the auger blade could be pulled back from inside the pipes.

In the current operation, the rescuers are using the American Auger 60-12000, a large and powerful horizontal directional drilling (HDD) machine manufactured by American Augers, a company specialising in trenchless underground construction equipment. The numbers “60-1200” refer to its drilling diameter capabilities. This machine is substantial in size and power, designed for heavy-duty horizontal drilling operations. Its drilling diameter range allows it to handle large-scale projects that require the installation of larger pipes, conduits, or utilities underground.

Like other horizontal auger machines, the 60-1200 employs trenchless technology, enabling it to create horizontal bores or tunnels underground without the need for extensive excavation or disruption to the surface. The machine can drill holes ranging from 5 feet to 10 feet in diameter.

What is the new hurdle?

In order to use the auger machine, the central shaft or drill stays outside, and the auger blade is attached to it to penetrate through the debris. In this case, the auger blade is passing through the mild steel pipes used to keep the passage intact.

After some hurdles faced in the last few days, the machine was reassembled and all augers were reinserted by 2.30 pm on Friday. Pushing for the 10th pipe started at 4.25 pm and the auger was already in by over 45 metres. According to a worker at Trenchless Engineer Services, the company that provided the machine, auger blades come in different lengths – 8, 6 and 3 metres. To reach a length of over 45 metres, several blades were attached to each other, using joints.

On Friday, a new obstruction was observed. When similar situations were faced earlier, the machine and the auger blades were pulled out so that someone could enter the pipes and check the obstruction manually.

The same thing was planned in this case. Rescuers started pulling back the machine to clear the pipes for manual inspection. But it appears that the tip of the blade was still stuck in the obstruction, and after pulling back around 15 metres, an auger joint broke. Around 32 metres of the auger blade is left inside the pipes, blocking them.

What needs to be done now?

Because there is no way to pull the broken auger blade, rescuers need to enter the 800 mm wide pipes, and cut the 32 metres long auger blade piece by piece to clear the path. According to officials, they have cut and removed almost 20 metres of the machine using gas cutters.

The rescuers have also called for a plasma cutter from Hyderabad, and it is expected to reach the tunnel site by Saturday night.

A plasma cutter is a tool used for cutting various types of electrically conductive materials, such as steel, aluminium, stainless steel, copper, and other metals. It works by creating a high-velocity jet of ionised gas, known as plasma, to melt and cut through the material.

According to the authorities, using the plasma cutters will increase the speed of cutting the machine. Currently, they have been able to cut the stuck auger just around 1.5 metres in an hour. With the plasma cutter, they can cut it around 4 metres in an hour.

Once the broken auger blade is removed, new auger blades will be used in its place.