This is a most amazing story. They have broken, not one, but two TBM's, in the same manner, and in the same place!
Because of high groundwater pressure and soft soils in the deep tunnel route, officials decided to use a new kind of machine rarely used in the United States. The machine pumps a liquid slurry in front of its cutting blades and then sends a mix of slurry and dirt through pipes to the surface.
Now they are trying to tack on some welds. The darn things are just going to break again, since they don't know what broke them in the first place. Judging by the conditions, and the depth (320 feet!), they have gone way beyond the Niagara Tunnel in adventurism. I wish them luck.