According to reports, the tunnel rescue operation has reached its final stretch. Various drilling methods were used in rescue operation.
From rat-hole mining to vertical drilling, numerous drilling methods have been used so far to rescue 41 workers trapped in the tunnel.
It is a manual drilling method and is carried out by skilled workers. This method is considered hazardous and is illegal in several countries.
It is done through boring machine. A vertical drill was bored into the ground and a pipe has been inserted to bring out workers.
It is a special tool to create underground tunnels without disturbing the ground. In Uttarakhand, the machine hit a metal obstruction & broke down.