Comparison of Surface Roughness and Transport Processes of Sawed, Split and Natural Sandstone Fractures
In single fractures, dispersion is often linked to the roughness of the fracture surfaces and the resulting local aperture distribution. To experimentally investigate the effects of diverse fracture types and surface morphologies in sandstones, three fractures were considered: those generated by saw...
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MDPI AG
2020-09-01
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| Series: | Water |
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| Online Access: | https://www.mdpi.com/2073-4441/12/9/2530 |
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| author | Sascha Frank Thomas Heinze Stefan Wohnlich |
| author_facet | Sascha Frank Thomas Heinze Stefan Wohnlich |
| author_sort | Sascha Frank |
| collection | DOAJ |
| description | In single fractures, dispersion is often linked to the roughness of the fracture surfaces and the resulting local aperture distribution. To experimentally investigate the effects of diverse fracture types and surface morphologies in sandstones, three fractures were considered: those generated by sawing and splitting, and a natural sedimentary fracture. The fracture surface morphologies were digitally analyzed and the hydraulic and transport parameters of the fractures were determined from Darcy and the tracer tests using a fit of a continuous time random walk (CTRW) and a classical advection–dispersion equation (ADE). While the sawed specimen with the smoothest surface had the smallest dispersivity, the natural fracture has the largest dispersivity due to strong anisotropy and non-matching fracture surfaces, although its surface roughness is comparable to the split specimen. The parameterization of the CTRW and of the ADE agree well for <i>β</i> > 4 of the truncated power law. For smaller values of <i>β</i>, non-Fickian transport processes are dominant. Channeling effects are observable in the tracer breakthrough curves. The transport behavior in the fractures is controlled by multiple constraints such as several surface roughness parameters and the equivalent hydraulic aperture. |
| first_indexed | 2024-03-10T16:25:04Z |
| format | Article |
| id | doaj.art-0224f535b0eb4345867be715f1cee6fc |
| institution | Directory Open Access Journal |
| issn | 2073-4441 |
| language | English |
| last_indexed | 2024-03-10T16:25:04Z |
| publishDate | 2020-09-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Water |
| spelling | doaj.art-0224f535b0eb4345867be715f1cee6fc2023-11-20T13:16:57ZengMDPI AGWater2073-44412020-09-01129253010.3390/w12092530Comparison of Surface Roughness and Transport Processes of Sawed, Split and Natural Sandstone FracturesSascha Frank0Thomas Heinze1Stefan Wohnlich2Faculty of Geosciences, Institute of Geology, Mineralogy and Geophysics, Applied Geology, Ruhr-University Bochum, 44801 Bochum, GermanyFaculty of Geosciences, Institute of Geology, Mineralogy and Geophysics, Applied Geology, Ruhr-University Bochum, 44801 Bochum, GermanyFaculty of Geosciences, Institute of Geology, Mineralogy and Geophysics, Applied Geology, Ruhr-University Bochum, 44801 Bochum, GermanyIn single fractures, dispersion is often linked to the roughness of the fracture surfaces and the resulting local aperture distribution. To experimentally investigate the effects of diverse fracture types and surface morphologies in sandstones, three fractures were considered: those generated by sawing and splitting, and a natural sedimentary fracture. The fracture surface morphologies were digitally analyzed and the hydraulic and transport parameters of the fractures were determined from Darcy and the tracer tests using a fit of a continuous time random walk (CTRW) and a classical advection–dispersion equation (ADE). While the sawed specimen with the smoothest surface had the smallest dispersivity, the natural fracture has the largest dispersivity due to strong anisotropy and non-matching fracture surfaces, although its surface roughness is comparable to the split specimen. The parameterization of the CTRW and of the ADE agree well for <i>β</i> > 4 of the truncated power law. For smaller values of <i>β</i>, non-Fickian transport processes are dominant. Channeling effects are observable in the tracer breakthrough curves. The transport behavior in the fractures is controlled by multiple constraints such as several surface roughness parameters and the equivalent hydraulic aperture.https://www.mdpi.com/2073-4441/12/9/2530tracer testssingle fracturedispersiondispersivitysurface roughnessfracture surface |
| spellingShingle | Sascha Frank Thomas Heinze Stefan Wohnlich Comparison of Surface Roughness and Transport Processes of Sawed, Split and Natural Sandstone Fractures Water tracer tests single fracture dispersion dispersivity surface roughness fracture surface |
| title | Comparison of Surface Roughness and Transport Processes of Sawed, Split and Natural Sandstone Fractures |
| title_full | Comparison of Surface Roughness and Transport Processes of Sawed, Split and Natural Sandstone Fractures |
| title_fullStr | Comparison of Surface Roughness and Transport Processes of Sawed, Split and Natural Sandstone Fractures |
| title_full_unstemmed | Comparison of Surface Roughness and Transport Processes of Sawed, Split and Natural Sandstone Fractures |
| title_short | Comparison of Surface Roughness and Transport Processes of Sawed, Split and Natural Sandstone Fractures |
| title_sort | comparison of surface roughness and transport processes of sawed split and natural sandstone fractures |
| topic | tracer tests single fracture dispersion dispersivity surface roughness fracture surface |
| url | https://www.mdpi.com/2073-4441/12/9/2530 |
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