Effect of unloading confining pressure rates on macroscopic and microscopic mechanisms in diorite based on PFC3D
IntroductionDeep underground excavation induces significant unloading damage in diorite, yet micromechanical mechanisms under varying unloading rates remain poorly understood.MethodsHerein, we employed the discrete element method to investigate the microscopic and macroscopic response mechanisms of...
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Frontiers Media S.A.
2025-06-01
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| Series: | Frontiers in Materials |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fmats.2025.1550403/full |
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| author | Xuexu An Juan Huang Xiaoxiao Duan Dengke Yang |
| author_facet | Xuexu An Juan Huang Xiaoxiao Duan Dengke Yang |
| author_sort | Xuexu An |
| collection | DOAJ |
| description | IntroductionDeep underground excavation induces significant unloading damage in diorite, yet micromechanical mechanisms under varying unloading rates remain poorly understood.MethodsHerein, we employed the discrete element method to investigate the microscopic and macroscopic response mechanisms of deep hard diorite samples during the loading and unloading process. We performed numerical analysis at three unloading-confining-pressure rates using PFC3D. The macroscopic mechanical characteristics, particle displacement, number of contact force chain failures, and propagation and evolution characteristics of the spatial distribution of tensile shear microcracks along the axial and radial directions of the samples during the loading and unloading process were studied.Results(1) Peak strength and strain increased with reduced unloading rates, while confining pressure exhibited instantaneous fluctuations during unloading, signaling progressive fracture evolution. (2) Radial particle displacement and contact force chain failures showed nonlinear concave growth from core to surface, intensifying post-peak—indicating severe near-surface damage. (3) Microcracks propagated inward from the unloading surface, with tensile cracks predominating over shear cracks. Tensile crack density increased as unloading rate decreased.DiscussionLower unloading rates facilitate prolonged stress redistribution, amplifying force chain failures and microcrack density. This confirms that unloading-induced damage initiates near boundaries and propagates inward, with tensile mechanisms governing failure. |
| format | Article |
| id | doaj-art-c60a09045b704feda7eb9edc40a53d18 |
| institution | Matheson Library |
| issn | 2296-8016 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | Frontiers Media S.A. |
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| series | Frontiers in Materials |
| spelling | doaj-art-c60a09045b704feda7eb9edc40a53d182025-06-27T08:58:35ZengFrontiers Media S.A.Frontiers in Materials2296-80162025-06-011210.3389/fmats.2025.15504031550403Effect of unloading confining pressure rates on macroscopic and microscopic mechanisms in diorite based on PFC3DXuexu An0Juan Huang1Xiaoxiao Duan2Dengke Yang3School of Railway Engineering, Shaanxi College of Communications Technology, Xi’an, ChinaSchool of Highway Engineering, Shaanxi College of Communications Technology, Xi’an, ChinaSchool of Intelligent Science and Engineering, Xi’an Peihua University, Xi’an, ChinaSchool of Intelligent Science and Engineering, Xi’an Peihua University, Xi’an, ChinaIntroductionDeep underground excavation induces significant unloading damage in diorite, yet micromechanical mechanisms under varying unloading rates remain poorly understood.MethodsHerein, we employed the discrete element method to investigate the microscopic and macroscopic response mechanisms of deep hard diorite samples during the loading and unloading process. We performed numerical analysis at three unloading-confining-pressure rates using PFC3D. The macroscopic mechanical characteristics, particle displacement, number of contact force chain failures, and propagation and evolution characteristics of the spatial distribution of tensile shear microcracks along the axial and radial directions of the samples during the loading and unloading process were studied.Results(1) Peak strength and strain increased with reduced unloading rates, while confining pressure exhibited instantaneous fluctuations during unloading, signaling progressive fracture evolution. (2) Radial particle displacement and contact force chain failures showed nonlinear concave growth from core to surface, intensifying post-peak—indicating severe near-surface damage. (3) Microcracks propagated inward from the unloading surface, with tensile cracks predominating over shear cracks. Tensile crack density increased as unloading rate decreased.DiscussionLower unloading rates facilitate prolonged stress redistribution, amplifying force chain failures and microcrack density. This confirms that unloading-induced damage initiates near boundaries and propagates inward, with tensile mechanisms governing failure.https://www.frontiersin.org/articles/10.3389/fmats.2025.1550403/fullnumerical analysisloading and unloadingparticle displacementcontact force chain failuremicrocrack evolution |
| spellingShingle | Xuexu An Juan Huang Xiaoxiao Duan Dengke Yang Effect of unloading confining pressure rates on macroscopic and microscopic mechanisms in diorite based on PFC3D Frontiers in Materials numerical analysis loading and unloading particle displacement contact force chain failure microcrack evolution |
| title | Effect of unloading confining pressure rates on macroscopic and microscopic mechanisms in diorite based on PFC3D |
| title_full | Effect of unloading confining pressure rates on macroscopic and microscopic mechanisms in diorite based on PFC3D |
| title_fullStr | Effect of unloading confining pressure rates on macroscopic and microscopic mechanisms in diorite based on PFC3D |
| title_full_unstemmed | Effect of unloading confining pressure rates on macroscopic and microscopic mechanisms in diorite based on PFC3D |
| title_short | Effect of unloading confining pressure rates on macroscopic and microscopic mechanisms in diorite based on PFC3D |
| title_sort | effect of unloading confining pressure rates on macroscopic and microscopic mechanisms in diorite based on pfc3d |
| topic | numerical analysis loading and unloading particle displacement contact force chain failure microcrack evolution |
| url | https://www.frontiersin.org/articles/10.3389/fmats.2025.1550403/full |
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