Inelastic compaction and permeability evolution in volcanic rock
Active volcanoes are mechanically dynamic environments, and edifice-forming material may often be subjected to significant amounts of stress and strain. It is understood that porous volcanic rock can compact inelastically under a wide range of in situ conditions. In this contribution, we explore the...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2017-04-01
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| Series: | Solid Earth |
| Online Access: | http://www.solid-earth.net/8/561/2017/se-8-561-2017.pdf |
| _version_ | 1818518226853691392 |
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| author | J. I. Farquharson P. Baud M. J. Heap |
| author_facet | J. I. Farquharson P. Baud M. J. Heap |
| author_sort | J. I. Farquharson |
| collection | DOAJ |
| description | Active volcanoes are mechanically dynamic environments, and
edifice-forming material may often be subjected to significant amounts of
stress and strain. It is understood that porous volcanic rock can compact
inelastically under a wide range of in situ conditions. In this
contribution, we explore the evolution of porosity and permeability –
critical properties influencing the style and magnitude of volcanic activity
– as a function of inelastic compaction of porous andesite under triaxial
conditions. Progressive axial strain accumulation is associated with
progressive porosity loss. The efficiency of compaction was found to be
related to the effective confining pressure under which deformation occurred:
at higher effective pressure, more porosity was lost for any given amount of
axial strain. Permeability evolution is more complex, with small amounts of
stress-induced compaction ( < 0.05, i.e. less than 5 % reduction in sample
length) yielding an increase in permeability under all effective pressures
tested, occasionally by almost 1 order of magnitude. This phenomenon is
considered here to be the result of improved connectivity of formerly
isolated porosity during triaxial loading. This effect is then overshadowed
by a decrease in permeability with further inelastic strain accumulation,
especially notable at high axial strains ( > 0.20) where samples may undergo
a reduction in permeability by 2 orders of magnitude relative to their
initial values. A physical limit to compaction is discussed, which we suggest
is echoed in a limit to the potential for permeability reduction in
compacting volcanic rock. Compiled literature data illustrate that at high
axial strain (both in the brittle and ductile regimes), porosity <i>ϕ</i> and
permeability <i>k</i> tend to converge towards intermediate values (i.e. 0.10
≤ <i>ϕ</i> ≤ 0.20; 10<sup>−14</sup> ≤ <i>k</i> ≤ 10<sup>−13</sup> m<sup>2</sup>). These results
are discussed in light of their potential ramifications for impacting edifice
outgassing – and in turn, eruptive activity – in active volcanoes. |
| first_indexed | 2024-12-11T01:07:07Z |
| format | Article |
| id | doaj.art-f2ae2973d50b4bba8c6a44a2518efef2 |
| institution | Directory Open Access Journal |
| issn | 1869-9510 1869-9529 |
| language | English |
| last_indexed | 2024-12-11T01:07:07Z |
| publishDate | 2017-04-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Solid Earth |
| spelling | doaj.art-f2ae2973d50b4bba8c6a44a2518efef22022-12-22T01:26:09ZengCopernicus PublicationsSolid Earth1869-95101869-95292017-04-018256158110.5194/se-8-561-2017Inelastic compaction and permeability evolution in volcanic rockJ. I. Farquharson0P. Baud1M. J. Heap2Institut de Physique de Globe de Strasbourg (UMR7516 CNRS), EOST, Université de Strasbourg, FranceInstitut de Physique de Globe de Strasbourg (UMR7516 CNRS), EOST, Université de Strasbourg, FranceInstitut de Physique de Globe de Strasbourg (UMR7516 CNRS), EOST, Université de Strasbourg, FranceActive volcanoes are mechanically dynamic environments, and edifice-forming material may often be subjected to significant amounts of stress and strain. It is understood that porous volcanic rock can compact inelastically under a wide range of in situ conditions. In this contribution, we explore the evolution of porosity and permeability – critical properties influencing the style and magnitude of volcanic activity – as a function of inelastic compaction of porous andesite under triaxial conditions. Progressive axial strain accumulation is associated with progressive porosity loss. The efficiency of compaction was found to be related to the effective confining pressure under which deformation occurred: at higher effective pressure, more porosity was lost for any given amount of axial strain. Permeability evolution is more complex, with small amounts of stress-induced compaction ( < 0.05, i.e. less than 5 % reduction in sample length) yielding an increase in permeability under all effective pressures tested, occasionally by almost 1 order of magnitude. This phenomenon is considered here to be the result of improved connectivity of formerly isolated porosity during triaxial loading. This effect is then overshadowed by a decrease in permeability with further inelastic strain accumulation, especially notable at high axial strains ( > 0.20) where samples may undergo a reduction in permeability by 2 orders of magnitude relative to their initial values. A physical limit to compaction is discussed, which we suggest is echoed in a limit to the potential for permeability reduction in compacting volcanic rock. Compiled literature data illustrate that at high axial strain (both in the brittle and ductile regimes), porosity <i>ϕ</i> and permeability <i>k</i> tend to converge towards intermediate values (i.e. 0.10 ≤ <i>ϕ</i> ≤ 0.20; 10<sup>−14</sup> ≤ <i>k</i> ≤ 10<sup>−13</sup> m<sup>2</sup>). These results are discussed in light of their potential ramifications for impacting edifice outgassing – and in turn, eruptive activity – in active volcanoes.http://www.solid-earth.net/8/561/2017/se-8-561-2017.pdf |
| spellingShingle | J. I. Farquharson P. Baud M. J. Heap Inelastic compaction and permeability evolution in volcanic rock Solid Earth |
| title | Inelastic compaction and permeability evolution in volcanic rock |
| title_full | Inelastic compaction and permeability evolution in volcanic rock |
| title_fullStr | Inelastic compaction and permeability evolution in volcanic rock |
| title_full_unstemmed | Inelastic compaction and permeability evolution in volcanic rock |
| title_short | Inelastic compaction and permeability evolution in volcanic rock |
| title_sort | inelastic compaction and permeability evolution in volcanic rock |
| url | http://www.solid-earth.net/8/561/2017/se-8-561-2017.pdf |
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