What challenges do tunnel supports face?

Tunnel supports face significant challenges, particularly when dealing with soft soil conditions. According to Austin Vernon on The Lunar Society, current boring machines must spend a considerable amount of time erecting supports to prevent the walls from caving in. This makes the process much slower compared to boring through hard rock, where the machines can operate continuously without as much need for support structures. The counterintuitive reality is that boring through hard rock is faster due to reduced downtime for support installation 1.