Microscopic Characteristics of Fractured Sandstone after Cyclic Freezing-Thawing and Triaxial Unloading Tests
The understanding of tunneling rock failure characteristics under unloading conditions in the cold region is critical for the proper design of rock tunneling support and mining safety operation. Given this understanding is currently limited, this study aimed to investigate the characteristics of fra...
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| Format: | Article |
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Wiley
2019-01-01
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| Series: | Advances in Civil Engineering |
| Online Access: | http://dx.doi.org/10.1155/2019/6512461 |
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| author | Xiaohui Ni Xiaomei Shen Zhende Zhu |
| author_facet | Xiaohui Ni Xiaomei Shen Zhende Zhu |
| author_sort | Xiaohui Ni |
| collection | DOAJ |
| description | The understanding of tunneling rock failure characteristics under unloading conditions in the cold region is critical for the proper design of rock tunneling support and mining safety operation. Given this understanding is currently limited, this study aimed to investigate the characteristics of fractured sandstone samples in the microscale after cyclic freezing-thawing and triaxial unloading tests. The samples were first subjected to different cycles of freezing and thawing, followed by the triaxial unloading test and scanning electron microscopy imaging. The peak strength and damage dilatancy stress were measured from the stress-strain curves. The microcrack characteristics (number, length, and width) were obtained through the image analysis. The results show that the decrease in peak strength and damage dilatancy stress was more significant by the first 20 freezing-thawing cycles when the pore pressure gradient is maximum compared to the later freezing-thawing cycles. The mechanical properties also significantly deteriorated when the severe freezing-thawing treatments were performed. The fracture section mainly had the morphology of honeycomb-like microstructure, stripped microstructure, and flocculent microstructure. The cracking extent was mainly influenced by the freezing-thawing rather than the triaxial unloading test, but the azimuthal angle of microcracks was significantly altered by the triaxial unloading. To properly design rock tunneling support and safe operation of mining in the cold region, both impact of cyclic freezing-thawing and the excavation operation direction should be considered. |
| format | Article |
| id | doaj-art-e8a0fe22f0344d258068345f88142fc7 |
| institution | Kabale University |
| issn | 1687-8086 1687-8094 |
| language | English |
| publishDate | 2019-01-01 |
| publisher | Wiley |
| record_format | Article |
| series | Advances in Civil Engineering |
| spelling | doaj-art-e8a0fe22f0344d258068345f88142fc72025-02-03T01:27:43ZengWileyAdvances in Civil Engineering1687-80861687-80942019-01-01201910.1155/2019/65124616512461Microscopic Characteristics of Fractured Sandstone after Cyclic Freezing-Thawing and Triaxial Unloading TestsXiaohui Ni0Xiaomei Shen1Zhende Zhu2College of Civil Engineering and Architecture, Jiaxing University, Jiaxing 314001, ChinaCollege of Civil Engineering and Architecture, Jiaxing University, Jiaxing 314001, ChinaGeotechnical Research Institute of Hohai University, Hohai University, Nanjing 210098, ChinaThe understanding of tunneling rock failure characteristics under unloading conditions in the cold region is critical for the proper design of rock tunneling support and mining safety operation. Given this understanding is currently limited, this study aimed to investigate the characteristics of fractured sandstone samples in the microscale after cyclic freezing-thawing and triaxial unloading tests. The samples were first subjected to different cycles of freezing and thawing, followed by the triaxial unloading test and scanning electron microscopy imaging. The peak strength and damage dilatancy stress were measured from the stress-strain curves. The microcrack characteristics (number, length, and width) were obtained through the image analysis. The results show that the decrease in peak strength and damage dilatancy stress was more significant by the first 20 freezing-thawing cycles when the pore pressure gradient is maximum compared to the later freezing-thawing cycles. The mechanical properties also significantly deteriorated when the severe freezing-thawing treatments were performed. The fracture section mainly had the morphology of honeycomb-like microstructure, stripped microstructure, and flocculent microstructure. The cracking extent was mainly influenced by the freezing-thawing rather than the triaxial unloading test, but the azimuthal angle of microcracks was significantly altered by the triaxial unloading. To properly design rock tunneling support and safe operation of mining in the cold region, both impact of cyclic freezing-thawing and the excavation operation direction should be considered.http://dx.doi.org/10.1155/2019/6512461 |
| spellingShingle | Xiaohui Ni Xiaomei Shen Zhende Zhu Microscopic Characteristics of Fractured Sandstone after Cyclic Freezing-Thawing and Triaxial Unloading Tests Advances in Civil Engineering |
| title | Microscopic Characteristics of Fractured Sandstone after Cyclic Freezing-Thawing and Triaxial Unloading Tests |
| title_full | Microscopic Characteristics of Fractured Sandstone after Cyclic Freezing-Thawing and Triaxial Unloading Tests |
| title_fullStr | Microscopic Characteristics of Fractured Sandstone after Cyclic Freezing-Thawing and Triaxial Unloading Tests |
| title_full_unstemmed | Microscopic Characteristics of Fractured Sandstone after Cyclic Freezing-Thawing and Triaxial Unloading Tests |
| title_short | Microscopic Characteristics of Fractured Sandstone after Cyclic Freezing-Thawing and Triaxial Unloading Tests |
| title_sort | microscopic characteristics of fractured sandstone after cyclic freezing thawing and triaxial unloading tests |
| url | http://dx.doi.org/10.1155/2019/6512461 |
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