Failure characteristics of unloading red shale with different bedding angles based on the particle discrete element

Failure characteristics of unloading red shale with different bedding angles based on the particle discrete element | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Failure characteristics of unloading red shale with different bedding angles based on the particle discrete element Chunhong Mao, Zhenqian Ma, Yuankun Zhu, Hui Wang, Yuxiang Bao This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7536460/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 03 Jan, 2026 Read the published version in Scientific Reports → Version 1 posted 20 You are reading this latest preprint version Abstract Understanding the unloading failure behavior of layered red shale is crucial for the stability of deep roadways and other underground structures. This study combines triaxial unloading experiments with discrete element method (DEM) simulations to reveal the mechanical, acoustic, and meso-mechanical responses of red shale with different bedding orientations. Laboratory tests demonstrate that unloading reduces peak strength by 15–25% compared with conventional triaxial loading, and that bedding angle critically controls the failure mode: 0° specimens exhibit shear-dominated failure, whereas 90° specimens tend to split in tension. The DEM model, calibrated with experimental results, reproduced stress–strain behavior with less than 2% error and captured the brittle–ductile transition. Acoustic emission (AE) analysis revealed a three-stage crack evolution process: gradual accumulation, rapid acceleration during unloading, and residual frictional growth. Under low confining pressures, AE activity was concentrated and intense, while higher pressures induced more continuous ductile-type emissions. Force-chain network analysis further showed that unloading accelerated crack coalescence and caused marked structural reorganization. Fabric anisotropy increased more than 25-fold, indicating stress-induced particle realignment, with normal contact forces dominating the response and tangential forces surging during shear failure. This integrated framework—linking AE monitoring, DEM simulation, and meso-mechanical fabric evolution—provides a robust basis for evaluating unloading-induced rock instability. The findings not only advance the understanding of bedding-controlled shale failure but also offer practical guidance for roadway support design, shale gas reservoir development, and underground engineering safety in layered rock masses. Physical sciences/Energy science and technology Physical sciences/Engineering Earth and environmental sciences/Solid earth sciences Discrete Element Method (DEM) Red Shale Unloading Failure Acoustic Emission Fabric Anisotropy Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 03 Jan, 2026 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 30 Sep, 2025 Reviews received at journal 28 Sep, 2025 Reviews received at journal 19 Sep, 2025 Reviewers agreed at journal 14 Sep, 2025 Reviewers agreed at journal 14 Sep, 2025 Reviews received at journal 14 Sep, 2025 Reviews received at journal 13 Sep, 2025 Reviews received at journal 11 Sep, 2025 Reviewers agreed at journal 11 Sep, 2025 Reviewers agreed at journal 11 Sep, 2025 Reviews received at journal 11 Sep, 2025 Reviewers agreed at journal 10 Sep, 2025 Reviewers agreed at journal 09 Sep, 2025 Reviewers agreed at journal 09 Sep, 2025 Reviewers agreed at journal 09 Sep, 2025 Reviewers invited by journal 09 Sep, 2025 Editor assigned by journal 09 Sep, 2025 Editor invited by journal 09 Sep, 2025 Submission checks completed at journal 08 Sep, 2025 First submitted to journal 08 Sep, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7536460","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":515910418,"identity":"0f9575bc-b65c-4df3-a53e-85faa4ea93da","order_by":0,"name":"Chunhong Mao","email":"","orcid":"","institution":"Guizhou University","correspondingAuthor":false,"prefix":"","firstName":"Chunhong","middleName":"","lastName":"Mao","suffix":""},{"id":515910419,"identity":"6d90d6ae-ab77-49d0-993e-05da69eb697a","order_by":1,"name":"Zhenqian Ma","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAtUlEQVRIiWNgGAWjYLCCDxDKgHgdjDNI1sLMQ5IW+fbsxM82v+oSG9ibt0kw1NwhwlE9bzdL5/axJTbwHCuTYDj2jAhHSeRukM7t4UlskMgxk2BsOExYC5tE7ubflj0SiQ3yb4jUwiORu02a4YcB0BYeIrVI8LzdZtnbkGDcxpNWbJFwjAgt8u25m2/8+FMn289+eOONDzVEaGFgSAAGWxvQU1A2kVoY/hCndBSMglEwCkYoAACj7DYgDpc+rwAAAABJRU5ErkJggg==","orcid":"","institution":"Guizhou University","correspondingAuthor":true,"prefix":"","firstName":"Zhenqian","middleName":"","lastName":"Ma","suffix":""},{"id":515910420,"identity":"42d24801-b2e6-469c-9b17-a8cef295983e","order_by":2,"name":"Yuankun Zhu","email":"","orcid":"","institution":"Guizhou University","correspondingAuthor":false,"prefix":"","firstName":"Yuankun","middleName":"","lastName":"Zhu","suffix":""},{"id":515910421,"identity":"59661788-7918-4f4c-8159-64a4e0186607","order_by":3,"name":"Hui Wang","email":"","orcid":"","institution":"Guizhou University","correspondingAuthor":false,"prefix":"","firstName":"Hui","middleName":"","lastName":"Wang","suffix":""},{"id":515910422,"identity":"6e2baefa-bf40-4846-9017-c5d761dd706d","order_by":4,"name":"Yuxiang Bao","email":"","orcid":"","institution":"Guizhou University","correspondingAuthor":false,"prefix":"","firstName":"Yuxiang","middleName":"","lastName":"Bao","suffix":""}],"badges":[],"createdAt":"2025-09-04 13:08:36","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7536460/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7536460/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-025-31022-0","type":"published","date":"2026-01-03T15:57:56+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":99545528,"identity":"41d519de-8592-43d9-956f-74abe3c47cf0","added_by":"auto","created_at":"2026-01-05 16:08:19","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1912327,"visible":true,"origin":"","legend":"","description":"","filename":"Maoetal.Manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7536460/v1_covered_9643e92c-9788-4689-8a9c-9a3fd82af4fc.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Failure characteristics of unloading red shale with different bedding angles based on the particle discrete element","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Discrete Element Method (DEM), Red Shale, Unloading Failure, Acoustic Emission, Fabric Anisotropy","lastPublishedDoi":"10.21203/rs.3.rs-7536460/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7536460/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eUnderstanding the unloading failure behavior of layered red shale is crucial for the stability of deep roadways and other underground structures. This study combines triaxial unloading experiments with discrete element method (DEM) simulations to reveal the mechanical, acoustic, and meso-mechanical responses of red shale with different bedding orientations. Laboratory tests demonstrate that unloading reduces peak strength by 15\u0026ndash;25% compared with conventional triaxial loading, and that bedding angle critically controls the failure mode: 0\u0026deg; specimens exhibit shear-dominated failure, whereas 90\u0026deg; specimens tend to split in tension. The DEM model, calibrated with experimental results, reproduced stress\u0026ndash;strain behavior with less than 2% error and captured the brittle\u0026ndash;ductile transition. Acoustic emission (AE) analysis revealed a three-stage crack evolution process: gradual accumulation, rapid acceleration during unloading, and residual frictional growth. Under low confining pressures, AE activity was concentrated and intense, while higher pressures induced more continuous ductile-type emissions. Force-chain network analysis further showed that unloading accelerated crack coalescence and caused marked structural reorganization. Fabric anisotropy increased more than 25-fold, indicating stress-induced particle realignment, with normal contact forces dominating the response and tangential forces surging during shear failure. This integrated framework\u0026mdash;linking AE monitoring, DEM simulation, and meso-mechanical fabric evolution\u0026mdash;provides a robust basis for evaluating unloading-induced rock instability. The findings not only advance the understanding of bedding-controlled shale failure but also offer practical guidance for roadway support design, shale gas reservoir development, and underground engineering safety in layered rock masses.\u003c/p\u003e","manuscriptTitle":"Failure characteristics of unloading red shale with different bedding angles based on the particle discrete element","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-18 09:46:40","doi":"10.21203/rs.3.rs-7536460/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-09-30T18:22:42+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-28T19:51:05+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-19T12:50:37+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"74710434814745593210869785511574559649","date":"2025-09-15T00:16:38+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"222380556831061516953128845364101539308","date":"2025-09-15T00:04:35+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-14T08:18:04+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-14T02:44:47+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-12T02:45:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"114482774554282336644887125155955067655","date":"2025-09-12T01:30:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"30006835043914143667074329482654290648","date":"2025-09-12T00:47:44+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-11T13:44:29+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"247469715579018826115199311367860865071","date":"2025-09-10T06:59:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"223370584017057578648252571358117151743","date":"2025-09-10T01:44:00+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"107947895823251935816313737538442929710","date":"2025-09-10T01:03:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"30297583763220833370899353277011461597","date":"2025-09-10T00:08:57+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-09T23:54:25+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-09T15:40:29+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-09-09T15:22:37+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-08T07:24:38+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-09-08T07:00:50+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"cb2e8de7-8316-470b-ad5a-cbf4d9e3ca5b","owner":[],"postedDate":"September 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":54807925,"name":"Physical sciences/Energy science and technology"},{"id":54807926,"name":"Physical sciences/Engineering"},{"id":54807927,"name":"Earth and environmental sciences/Solid earth sciences"}],"tags":[],"updatedAt":"2026-01-05T16:05:26+00:00","versionOfRecord":{"articleIdentity":"rs-7536460","link":"https://doi.org/10.1038/s41598-025-31022-0","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2026-01-03 15:57:56","publishedOnDateReadable":"January 3rd, 2026"},"versionCreatedAt":"2025-09-18 09:46:40","video":"","vorDoi":"10.1038/s41598-025-31022-0","vorDoiUrl":"https://doi.org/10.1038/s41598-025-31022-0","workflowStages":[]},"version":"v1","identity":"rs-7536460","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7536460","identity":"rs-7536460","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}