The Oil Drum

Those of you that have been following the reports of the trapped miners at the Crandall Canyon Mine in Utah may have read that there is some debate as to whether the incident was caused by the mining itself, or whether it was a naturally induced earthquake. Also you may not understand what the mine is describing as “retreat mining.” And so I thought to write a short description that explains both, without dealing specifically with the details of what is happening in Utah, for which I do not have specific information. There is, however, a basic mine map at the NYT site that I am going to use as a reference.

The latest information from the MSHA website reports

Friday, August 10, 7 a.m. EDT
The small vertical drill bit punched through to the mine on Thursday night at 11:57 pm EDT. The large rotary drill has reached a depth of 1,016 feet. A microphone was lowered into the cavity through the drill stem, and no human noise was detected.

UPDATE: One of the questions that arises in this type of situation is to see what caused the blockage of the passageways to where the miners were working. If you look at the first picture in the Reuters series shown on Friday it would appear that the rubble pile is caused by the floor lifting. This is the equivalent of the pillars punching through the floor, which they could do if they were loaded up, since the floor can be the weakest of the three components (roof, coal and floor rock). If this is the case, it is not clear how extensive that blockage is. But you can see that the roof rock appears intact. They may well have run the drill down through the cavity to see how much room there is in the area where the men are expected to be.