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 Post subject: Odds of Subsidence while in a mine...
PostPosted: Thu Oct 05, 2006 2:04 pm 
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Joined: Thu Sep 21, 2006 1:05 am
Posts: 20
Does weather or age of mine affect this? Are mines that are hewn out of rock less likely to collapse?


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 Post subject:
PostPosted: Thu Oct 05, 2006 2:28 pm 
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Joined: Fri Jul 15, 2005 2:34 pm
Posts: 6872
Location: Within 60 Miles of the Northern Anthracite Field
Frank has some good points but also to point out that most subsidences happen in workings that are close to the surface, this is caused by, running water, freezing and thawing ground, small sizemic events, rain water seeping through to name a few. we have seen a few places where subsidences into workings were only 8-10 feet below the surface. in steeply pitching coal mines subsidences usually happen where the coal face deteriorates and it is close to the surface causing a crop fall, or chute opening to the surface. many mines actually did this for ventilation purposes. in flat pitch mines they are usually caused by simply mining too close to the surface. in archbald there was a subsidence directly below the rr tracks, and there is a manway entrace near. so we went in the manway then saw where they filled the subsidence with concrete. that was pretty cool. check this out....

http://www.undergroundminers.com/subsidenceindex.html

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 Post subject:
PostPosted: Sun Oct 08, 2006 6:52 am 
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Joined: Mon Jun 20, 2005 11:33 pm
Posts: 3080
Location: Above the Sterling Hill Mine
Did you ever get pictures of the concrete fill from under the ground in Gravity? It would be interesting to see actually...

Miner Greg


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 Post subject:
PostPosted: Sun Oct 08, 2006 7:22 am 
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Joined: Mon May 08, 2006 2:16 pm
Posts: 1500
Location: Central Ohio
In our coal mines the roof fails for several reasons. Most are deep enough 100-300' ft below. We just have really bad roofs. Most of the newer mines have roof bolts or I-beams or concrete if we are really lucky. We have pics that still show collapses dispite the bolting & I-beams. We do not have hard rock most of the time it is sandstone, shale or what ever soft rock is above the coal seams. This makes it really difficult but our mines are extreamly high production because the seams are flat and most of the time consistant seam thicknesses 4'-20'. This is a good thing because this will allow us to use long wall miners ( A cutting machine that cuts up to 1250 ft wide). This machine processes the coal at an unbelievable rate but the roof collapses behind it as it moves. Now that is very interesting to actually hear & watch the roof fall behind you. The downside is that you can not explore these mines only the main haulage routes. Our mines are the mines that keep the lights on! Just because of the high production.

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 Post subject:
PostPosted: Sun Oct 08, 2006 8:18 pm 
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Joined: Fri Jul 15, 2005 2:34 pm
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Location: Within 60 Miles of the Northern Anthracite Field
also to point out that the bituminous coal mines collapse more because the coal is softer and pillars crush out alot easier, in room and pillar method of course.

chris

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PostPosted: Sun Oct 08, 2006 8:23 pm 
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Location: Central Ohio
Actually your not supposed to put the pillars on the coal surface but it does happen. The miners put the pillars on the rock face but that is still usually soft, remember the dual track haulage tunnel where the roof let go in a couple of places.

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