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Abstract The formation of compaction bands could greatly reduce the permeability of rocks，which has potential economic value. In order to research the characteristic of permeability change during the formation of compaction band，permeability change with confining pressure unloading and the relation between volumetric strain and permeability change，weathered high-porosity rocks are used to carry out triaxial compression tests and obtained the permeability during the processes. Discrete compaction bands，high-angle shear bands，and the hybrid modes of two of the three involving discrete compaction bands，diffuse compaction bands and high-angle compaction bands are observed；three patterns of permeability change have been also observed. The permeability reduces with the increase of axial strain，the permeability suddenly reduces when the first localization compaction band formes. The reduction of permeability is blow 2 orders of magnitude，and most is blow 1 order of magnitude. This is lower than other results of 2—3 orders of magnitude；but it is consistent with the result of no severe grain crushing. The volume of the samples dilates but the permeability reduces at the later loading stage. So，there may exist the phenomenon of permeability reduction with the porosity increase. There are different patterns of permeability change during the process of confining pressure unloading. The permeability of some samples consistently increases with the decrease of confining pressure，and the increase speed is also increase. Another pattern is that the permeability decreases first and then increases with the decrease of confining pressure.
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Received: 23 December 2010
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2011, Vol. 30 
