http://coalgeology.com/photograph-problem-with-packers/2629/ Mining, Clean Energy, Going Green to Climate Change Fri, 27 Apr 2012 04:04:49 +0000 hourly 1 http://wordpress.org/?v=3.3.2 http://coalgeology.com/photograph-problem-with-packers/2629/comment-page-1/#comment-316 mori salehi Sat, 28 Nov 2009 05:21:01 +0000 http://coalgeology.com/?p=2629#comment-316 The plastic behaviour of certain rocks such as conglomerates, breccia, and very coarse grained s.stones and coal and shale may be one of the factor causing the bending, particlarly when the drilling is deep and the diameter of drilling rods are less than 50 cm. The plastic behaviour of certain rocks such as conglomerates, breccia, and very coarse grained s.stones and coal and shale may be one of the factor causing the bending, particlarly when the drilling is deep and the diameter of drilling rods are less than 50 cm.

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