Influence of Confining Pressure Unloading Rate on the Strength Characteristics and Fracture Process of Granite Using Lab Tests
In order to study the mechanical behaviors and fracture process properties of granite under confining pressure unloading with constant axial pressure, RMT-150B rock mechanics test system and acoustic emission detector were used to study the mechanical properties and fracture process characteristics...
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| Format: | Article |
| Language: | English |
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Wiley
2021-01-01
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| Series: | Advances in Materials Science and Engineering |
| Online Access: | http://dx.doi.org/10.1155/2021/7925608 |
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| author | Jiaqi Guo Pengfei Liu Junqi Fan Xiaoyan Shi Xin Huang |
| author_facet | Jiaqi Guo Pengfei Liu Junqi Fan Xiaoyan Shi Xin Huang |
| author_sort | Jiaqi Guo |
| collection | DOAJ |
| description | In order to study the mechanical behaviors and fracture process properties of granite under confining pressure unloading with constant axial pressure, RMT-150B rock mechanics test system and acoustic emission detector were used to study the mechanical properties and fracture process characteristics of deeply buried granite specimens under different combinations of initial confining pressures and unloading rates. The results show that when the unloading rate is small, the deviatoric stress-strain curve of granite specimens will yield an unloading platform, and the specimens show significant characteristics of ductility; when the unloading rate is large, the specimens show characteristics of brittleness. Besides, the axial strain rate increases with the increase of initial confining pressure and unloading rate, and the axial strain rate fluctuates. The ratio of axial strain increment to confining pressure increment of granite specimens decreases with the increase of the unloading rate, and a faster unloading rate and a higher initial confining pressure will restrain the axial deformation of granite sample. The normalized confining pressure decreased parameter of granite specimen increases with the increase of initial confining pressure. When the unloading rate is relatively high, it plays a dominant role in the compressive strength of granite specimens. The Mohr–Coulomb strength criterion can better reflect the strength characteristics of specimens under confining pressure unloading. The cohesion of granite specimens decreases with the increase of unloading rate, and the internal friction angle increases with the increase of unloading rate. Notably, the unloading rate presents a weakening effect on the cohesion of the specimen and a strengthening effect on the internal friction angle of the specimen, and the former effect is stronger than the latter one. When the unloading rate is small, the acoustic emission ringing count increases more evenly, and the deformation and damage of the specimen develop slowly; when the unloading rate is high, the acoustic emission ringing count increases to the maximum instantaneously at the initial stage of confining pressure unloading, and the specimen is damaged rapidly, showing the characteristic of sudden fracture. The fracture mode of granite specimens is affected by the unloading rate and initial confining pressure. At the same unloading rate, the specimens with high initial confining pressure show typical tensile fracture characteristics, while the specimens with low initial confining pressure mainly suffer from shear fracture or shear-tension composite fracture. With the increase of unloading rate, the fracture characteristics of specimens show a transition from shear or shear-tension composite fracture to tensile fracture. |
| format | Article |
| id | doaj-art-b4fb8e947be749488810596e29bf83d0 |
| institution | OA Journals |
| issn | 1687-8434 1687-8442 |
| language | English |
| publishDate | 2021-01-01 |
| publisher | Wiley |
| record_format | Article |
| series | Advances in Materials Science and Engineering |
| spelling | doaj-art-b4fb8e947be749488810596e29bf83d02025-08-20T02:23:31ZengWileyAdvances in Materials Science and Engineering1687-84341687-84422021-01-01202110.1155/2021/79256087925608Influence of Confining Pressure Unloading Rate on the Strength Characteristics and Fracture Process of Granite Using Lab TestsJiaqi Guo0Pengfei Liu1Junqi Fan2Xiaoyan Shi3Xin Huang4School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454000, ChinaSchool of Civil Engineering, Henan Polytechnic University, Jiaozuo 454000, ChinaResearch Institute for National Defense Engineering of Academy of Military Science PLA China, Luoyang 471023, ChinaResearch Institute for National Defense Engineering of Academy of Military Science PLA China, Luoyang 471023, ChinaSchool of Civil Engineering, Henan Polytechnic University, Jiaozuo 454000, ChinaIn order to study the mechanical behaviors and fracture process properties of granite under confining pressure unloading with constant axial pressure, RMT-150B rock mechanics test system and acoustic emission detector were used to study the mechanical properties and fracture process characteristics of deeply buried granite specimens under different combinations of initial confining pressures and unloading rates. The results show that when the unloading rate is small, the deviatoric stress-strain curve of granite specimens will yield an unloading platform, and the specimens show significant characteristics of ductility; when the unloading rate is large, the specimens show characteristics of brittleness. Besides, the axial strain rate increases with the increase of initial confining pressure and unloading rate, and the axial strain rate fluctuates. The ratio of axial strain increment to confining pressure increment of granite specimens decreases with the increase of the unloading rate, and a faster unloading rate and a higher initial confining pressure will restrain the axial deformation of granite sample. The normalized confining pressure decreased parameter of granite specimen increases with the increase of initial confining pressure. When the unloading rate is relatively high, it plays a dominant role in the compressive strength of granite specimens. The Mohr–Coulomb strength criterion can better reflect the strength characteristics of specimens under confining pressure unloading. The cohesion of granite specimens decreases with the increase of unloading rate, and the internal friction angle increases with the increase of unloading rate. Notably, the unloading rate presents a weakening effect on the cohesion of the specimen and a strengthening effect on the internal friction angle of the specimen, and the former effect is stronger than the latter one. When the unloading rate is small, the acoustic emission ringing count increases more evenly, and the deformation and damage of the specimen develop slowly; when the unloading rate is high, the acoustic emission ringing count increases to the maximum instantaneously at the initial stage of confining pressure unloading, and the specimen is damaged rapidly, showing the characteristic of sudden fracture. The fracture mode of granite specimens is affected by the unloading rate and initial confining pressure. At the same unloading rate, the specimens with high initial confining pressure show typical tensile fracture characteristics, while the specimens with low initial confining pressure mainly suffer from shear fracture or shear-tension composite fracture. With the increase of unloading rate, the fracture characteristics of specimens show a transition from shear or shear-tension composite fracture to tensile fracture.http://dx.doi.org/10.1155/2021/7925608 |
| spellingShingle | Jiaqi Guo Pengfei Liu Junqi Fan Xiaoyan Shi Xin Huang Influence of Confining Pressure Unloading Rate on the Strength Characteristics and Fracture Process of Granite Using Lab Tests Advances in Materials Science and Engineering |
| title | Influence of Confining Pressure Unloading Rate on the Strength Characteristics and Fracture Process of Granite Using Lab Tests |
| title_full | Influence of Confining Pressure Unloading Rate on the Strength Characteristics and Fracture Process of Granite Using Lab Tests |
| title_fullStr | Influence of Confining Pressure Unloading Rate on the Strength Characteristics and Fracture Process of Granite Using Lab Tests |
| title_full_unstemmed | Influence of Confining Pressure Unloading Rate on the Strength Characteristics and Fracture Process of Granite Using Lab Tests |
| title_short | Influence of Confining Pressure Unloading Rate on the Strength Characteristics and Fracture Process of Granite Using Lab Tests |
| title_sort | influence of confining pressure unloading rate on the strength characteristics and fracture process of granite using lab tests |
| url | http://dx.doi.org/10.1155/2021/7925608 |
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