Experimental investigation of stress unloading effects on rock damage and confining pressure-dependent crack initiation stress of porous sandstone under true triaxial stress environments
This study investigates the impact of intermediate (σ2) and minimum (σ3) principal stress unloading on damage behavior and the confining pressure influence on crack initiation stress (σci) in true triaxial stress conditions, utilizing large-scale cubic samples. Two distinct true triaxial tests were...
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
KeAi Communications Co., Ltd.
2024-04-01
|
| Series: | Rock Mechanics Bulletin |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2773230424000106 |
| _version_ | 1827319175356350464 |
|---|---|
| author | Qingsheng Bai Max Friedel Heinz Konietzky |
| author_facet | Qingsheng Bai Max Friedel Heinz Konietzky |
| author_sort | Qingsheng Bai |
| collection | DOAJ |
| description | This study investigates the impact of intermediate (σ2) and minimum (σ3) principal stress unloading on damage behavior and the confining pressure influence on crack initiation stress (σci) in true triaxial stress conditions, utilizing large-scale cubic samples. Two distinct true triaxial tests were executed, examining the effects of confining stress (σ2 and σ3) unloading on porous sandstone damage and the correlation between confining stress and σci. Acoustic emission (AE) parameters, signal characteristics, and wave velocity variations were utilized to elucidate cracking mechanisms and damage development in the samples. Unloading tests reveal consistent velocities in three orthogonal directions (V11, V22, and V33) during the initial two unloading stages. In the subsequent three stages, confining stress unloading leads to a decrease in wave velocity in the corresponding direction, while velocities in the other two directions remain nearly constant. Notably, σ2 unloading generates higher amplitude AE signals compared to σ3 unloading, with over 70% of the micro-cracks categorized as tensile. In the incremental loading tests, σci is found to be contingent on confining pressure, with σ2 playing a crucial role. During σ1 loading, V33 decreases, indicating additional crack formation; conversely, σ3 loading results in V33 increase, signifying the continuous closure of existing cracks. Limitations of the experiments are summarized and prospects in this domain are outlined. |
| first_indexed | 2024-04-25T00:15:33Z |
| format | Article |
| id | doaj.art-2a6c1578678c4f7691a07d69405c664c |
| institution | Directory Open Access Journal |
| issn | 2773-2304 |
| language | English |
| last_indexed | 2024-04-25T00:15:33Z |
| publishDate | 2024-04-01 |
| publisher | KeAi Communications Co., Ltd. |
| record_format | Article |
| series | Rock Mechanics Bulletin |
| spelling | doaj.art-2a6c1578678c4f7691a07d69405c664c2024-03-13T04:46:35ZengKeAi Communications Co., Ltd.Rock Mechanics Bulletin2773-23042024-04-0132100111Experimental investigation of stress unloading effects on rock damage and confining pressure-dependent crack initiation stress of porous sandstone under true triaxial stress environmentsQingsheng Bai0Max Friedel1Heinz Konietzky2Corresponding author.; Geotechnical Institute, TU Bergakademie Freiberg, Gustav-Zeuner-Straße 1, 09599 Freiberg, GermanyGeotechnical Institute, TU Bergakademie Freiberg, Gustav-Zeuner-Straße 1, 09599 Freiberg, GermanyGeotechnical Institute, TU Bergakademie Freiberg, Gustav-Zeuner-Straße 1, 09599 Freiberg, GermanyThis study investigates the impact of intermediate (σ2) and minimum (σ3) principal stress unloading on damage behavior and the confining pressure influence on crack initiation stress (σci) in true triaxial stress conditions, utilizing large-scale cubic samples. Two distinct true triaxial tests were executed, examining the effects of confining stress (σ2 and σ3) unloading on porous sandstone damage and the correlation between confining stress and σci. Acoustic emission (AE) parameters, signal characteristics, and wave velocity variations were utilized to elucidate cracking mechanisms and damage development in the samples. Unloading tests reveal consistent velocities in three orthogonal directions (V11, V22, and V33) during the initial two unloading stages. In the subsequent three stages, confining stress unloading leads to a decrease in wave velocity in the corresponding direction, while velocities in the other two directions remain nearly constant. Notably, σ2 unloading generates higher amplitude AE signals compared to σ3 unloading, with over 70% of the micro-cracks categorized as tensile. In the incremental loading tests, σci is found to be contingent on confining pressure, with σ2 playing a crucial role. During σ1 loading, V33 decreases, indicating additional crack formation; conversely, σ3 loading results in V33 increase, signifying the continuous closure of existing cracks. Limitations of the experiments are summarized and prospects in this domain are outlined.http://www.sciencedirect.com/science/article/pii/S2773230424000106Stress unloadingDamage behaviorTrue triaxial stress environmentsWave velocityCrack initiation stress |
| spellingShingle | Qingsheng Bai Max Friedel Heinz Konietzky Experimental investigation of stress unloading effects on rock damage and confining pressure-dependent crack initiation stress of porous sandstone under true triaxial stress environments Rock Mechanics Bulletin Stress unloading Damage behavior True triaxial stress environments Wave velocity Crack initiation stress |
| title | Experimental investigation of stress unloading effects on rock damage and confining pressure-dependent crack initiation stress of porous sandstone under true triaxial stress environments |
| title_full | Experimental investigation of stress unloading effects on rock damage and confining pressure-dependent crack initiation stress of porous sandstone under true triaxial stress environments |
| title_fullStr | Experimental investigation of stress unloading effects on rock damage and confining pressure-dependent crack initiation stress of porous sandstone under true triaxial stress environments |
| title_full_unstemmed | Experimental investigation of stress unloading effects on rock damage and confining pressure-dependent crack initiation stress of porous sandstone under true triaxial stress environments |
| title_short | Experimental investigation of stress unloading effects on rock damage and confining pressure-dependent crack initiation stress of porous sandstone under true triaxial stress environments |
| title_sort | experimental investigation of stress unloading effects on rock damage and confining pressure dependent crack initiation stress of porous sandstone under true triaxial stress environments |
| topic | Stress unloading Damage behavior True triaxial stress environments Wave velocity Crack initiation stress |
| url | http://www.sciencedirect.com/science/article/pii/S2773230424000106 |
| work_keys_str_mv | AT qingshengbai experimentalinvestigationofstressunloadingeffectsonrockdamageandconfiningpressuredependentcrackinitiationstressofporoussandstoneundertruetriaxialstressenvironments AT maxfriedel experimentalinvestigationofstressunloadingeffectsonrockdamageandconfiningpressuredependentcrackinitiationstressofporoussandstoneundertruetriaxialstressenvironments AT heinzkonietzky experimentalinvestigationofstressunloadingeffectsonrockdamageandconfiningpressuredependentcrackinitiationstressofporoussandstoneundertruetriaxialstressenvironments |