Fractal Characteristics of Coal and Sandstone Failure under Different Unloading Confining Pressure Tests
To analyze the fractal characteristics of coal rock failure under unloading conditions, triaxial unloading confining pressure tests were carried out on coal and sandstone rock samples under different unloading rates and initial confining pressures. We examined the distribution of the surface cracks...
Saved in:
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2020-01-01
|
| Series: | Advances in Materials Science and Engineering |
| Online Access: | http://dx.doi.org/10.1155/2020/2185492 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1850221574633816064 |
|---|---|
| author | Tianran Ma Depeng Ma Yongjie Yang |
| author_facet | Tianran Ma Depeng Ma Yongjie Yang |
| author_sort | Tianran Ma |
| collection | DOAJ |
| description | To analyze the fractal characteristics of coal rock failure under unloading conditions, triaxial unloading confining pressure tests were carried out on coal and sandstone rock samples under different unloading rates and initial confining pressures. We examined the distribution of the surface cracks and fragmentation of the coal and sandstone samples that failed under different triaxial unloading confining pressure tests. The results showed that the fractal dimension of the surface cracks in coal and sandstone decreased as the initial unloading confining pressure increased. Thus, shear failure is more obvious in coal or sandstone with high-stress conditions caused by unloading confining pressure than in coal or sandstone with low-stress conditions. However, the fractal dimension of the surface cracks increased with the unloading rates. Additionally, the fractal dimension of the fragmentation in the coal and sandstone samples had a negative correlation with the initial unloading confining pressure. When the initial confining pressure was relatively low, the samples underwent splitting and shear failure; when the initial confining pressure was higher, the failure mode was mostly shear failure and the fragmentation of the samples was less homogeneous. In contrast, the fractal dimension of the fragmentation in the coal and sandstone increased with higher unloading rates. The lithology had a significant effect on the fractal dimension of the surface cracks and on the fragmentation. Samples with more internal fissures had more surface cracks and the fragmentation was more homogeneous when the rock failed compared with samples with less fissures under the same experimental conditions. |
| format | Article |
| id | doaj-art-68375cd4784d4e5d89504b7e60f00b69 |
| institution | OA Journals |
| issn | 1687-8434 1687-8442 |
| language | English |
| publishDate | 2020-01-01 |
| publisher | Wiley |
| record_format | Article |
| series | Advances in Materials Science and Engineering |
| spelling | doaj-art-68375cd4784d4e5d89504b7e60f00b692025-08-20T02:06:42ZengWileyAdvances in Materials Science and Engineering1687-84341687-84422020-01-01202010.1155/2020/21854922185492Fractal Characteristics of Coal and Sandstone Failure under Different Unloading Confining Pressure TestsTianran Ma0Depeng Ma1Yongjie Yang2State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou 221116, ChinaCollege of Water Conservancy and Civil Engineering, Shandong Agricultural University, Tai’an 271018, ChinaCollege of Mining and Safety Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaTo analyze the fractal characteristics of coal rock failure under unloading conditions, triaxial unloading confining pressure tests were carried out on coal and sandstone rock samples under different unloading rates and initial confining pressures. We examined the distribution of the surface cracks and fragmentation of the coal and sandstone samples that failed under different triaxial unloading confining pressure tests. The results showed that the fractal dimension of the surface cracks in coal and sandstone decreased as the initial unloading confining pressure increased. Thus, shear failure is more obvious in coal or sandstone with high-stress conditions caused by unloading confining pressure than in coal or sandstone with low-stress conditions. However, the fractal dimension of the surface cracks increased with the unloading rates. Additionally, the fractal dimension of the fragmentation in the coal and sandstone samples had a negative correlation with the initial unloading confining pressure. When the initial confining pressure was relatively low, the samples underwent splitting and shear failure; when the initial confining pressure was higher, the failure mode was mostly shear failure and the fragmentation of the samples was less homogeneous. In contrast, the fractal dimension of the fragmentation in the coal and sandstone increased with higher unloading rates. The lithology had a significant effect on the fractal dimension of the surface cracks and on the fragmentation. Samples with more internal fissures had more surface cracks and the fragmentation was more homogeneous when the rock failed compared with samples with less fissures under the same experimental conditions.http://dx.doi.org/10.1155/2020/2185492 |
| spellingShingle | Tianran Ma Depeng Ma Yongjie Yang Fractal Characteristics of Coal and Sandstone Failure under Different Unloading Confining Pressure Tests Advances in Materials Science and Engineering |
| title | Fractal Characteristics of Coal and Sandstone Failure under Different Unloading Confining Pressure Tests |
| title_full | Fractal Characteristics of Coal and Sandstone Failure under Different Unloading Confining Pressure Tests |
| title_fullStr | Fractal Characteristics of Coal and Sandstone Failure under Different Unloading Confining Pressure Tests |
| title_full_unstemmed | Fractal Characteristics of Coal and Sandstone Failure under Different Unloading Confining Pressure Tests |
| title_short | Fractal Characteristics of Coal and Sandstone Failure under Different Unloading Confining Pressure Tests |
| title_sort | fractal characteristics of coal and sandstone failure under different unloading confining pressure tests |
| url | http://dx.doi.org/10.1155/2020/2185492 |
| work_keys_str_mv | AT tianranma fractalcharacteristicsofcoalandsandstonefailureunderdifferentunloadingconfiningpressuretests AT depengma fractalcharacteristicsofcoalandsandstonefailureunderdifferentunloadingconfiningpressuretests AT yongjieyang fractalcharacteristicsofcoalandsandstonefailureunderdifferentunloadingconfiningpressuretests |