Speaking as the person who built the TBM’s for the Chunnel as well as the ones for the Seattle Bus tunnel.
Sounds to me like they may have a bearing problem in the head. Or could be bad sensors. I found that 50% of the problems were do to the sensors going bad(just like of your car).
That's what I thought, too. Maybe the steel pipe put an over-limit side load on one of the bearings.
Or, it could be this.
Seattle Tunnel Drill Uncovers Possible Alien Activities
http://www.agoracosmopolitan.com/news/ufo_extraterrestrials/2013/12/27/7434.html
Snip
Many speculated that Big Bertha could have hit the side walls of one of the many alien bases on Earth.
Feliks Banel, Seattle’s historian elaborated on the history of the place 100 years ago. As a working waterfront, the object could be a part of a locomotive or a part of an old ship. However, he also did not discount the possibility of the presence of UFOs and extra-terrestrial activities.
“Maybe it’s some ancient artifact, maybe there is an ancient civilization here that goes way back that nobody’s even considered.”
Earlier articles had WSDOT talking to the operators and telling them they thought it was operating at too high of temperatures awhile ago - weeks before it hit the pipe and then a few days later was stopped.
But WSDOT was saying how they can only make comments, as the STP owners are the folks that make the final decisions (and therefore remain liable).
The “bad sensor” thing might be correct, but it reminds me of the failed gas line and explosion we had north of Seattle due to a “bad sensor software”. Had to do with the Y2K changes in software. After so many false alarms going off about a closed valve on a major gasoline pipeline, the operators ignored it. It WAS close, the thing ruptured and blew up, kill two people in a county park.
Sorry for the aside, but I hope if they think it is the sensors they replace them or troubleshoot them. And not try the old “Oh - ignore that, it is just a bad sensor” thing!
I can’t imagine - being stopped for almost a month now (since Dec. 6) and only going 800 feet or so. I wonder what surprises are in store for them the remaining x thousands of feet.