What they use these machines for normally is to drill shafts for ventilation or egress in mines. Generally there are two ways to drill shafts, top down (blind s

What they use these machines for normally is to drill shafts for ventilation or egress in mines. Generally there are two ways to drill shafts, top down (blind sinking etc.) or bottom up (raiseboring). Top down shafts used to be predominate, but these days they are only used for larger shaft diameters 5.5m+. What you do is drill a pilot hole down for the shaft, attach the reamer head, then literally pull the drill rig upwards to ream the hole. Obviously in this case we can't get the reamer down there so they are using the pilot shaft hole to get the guys out (hence the tiny capsule!) The rig (Strata 950) is used all over the world for these jobs, and it wasn't specifically designed for this, it just happened to be there at the time. The major design considerations were the massive forces and torques that would be applied. However the biggest worry we had was the impact and fatigue strength of the rig, especially the reamer. This thing has upwards of 500T of thrust pulling it up and 600kNm of Torque on a 5.5m head. If it encounters a void or some other ground anomaly and it stalls or hits something, the damage it can cause is massive. It has been a while but I remember 25mm welds throughout it. Hope that wasn't too long winded, but it is as 'simple' as I could really make it during my lunch break. edit: some clarification