Analysis of fractures of a hard rock specimen via unloading of central hole with different sectional shapes
Abstract Hard rock failure and rockburst hazards under high in situ stresses have been the subject of deep rock mechanics and engineering. Previous investigations employed cubic rock specimens with a central hole for simulation of rock fracturing around deep tunnels at a laboratory scale, while the...
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doaj-c5892b5212a945099b2990bf5e5b70712020-11-25T01:48:50ZengWileyEnergy Science & Engineering2050-05052019-12-01762265228610.1002/ese3.432Analysis of fractures of a hard rock specimen via unloading of central hole with different sectional shapesFan Feng0Shaojie Chen1Diyuan Li2Songtao Hu3Wanpeng Huang4Bo Li5College of Mining and Safety Engineering Shandong University and Science and Technology Qingdao Shandong ChinaCollege of Mining and Safety Engineering Shandong University and Science and Technology Qingdao Shandong ChinaSchool of Resources and Safety Engineering Central South University Changsha Hunan ChinaShandong Provincial geo‐mineral Engineering Co. Ltd Jinan Shandong ChinaCollege of Mining and Safety Engineering Shandong University and Science and Technology Qingdao Shandong ChinaCollege of Mining and Safety Engineering Shandong University and Science and Technology Qingdao Shandong ChinaAbstract Hard rock failure and rockburst hazards under high in situ stresses have been the subject of deep rock mechanics and engineering. Previous investigations employed cubic rock specimens with a central hole for simulation of rock fracturing around deep tunnels at a laboratory scale, while the failure characteristics and crack evolution behavior around different shapes of holes induced by excavation unloading response have been barely considered. A commercially combined finite‐discrete element method (combined FEM/DEM) was used to investigate the failure characteristics and crack propagation process of typical hard rock specimens (marble) via the unloading of central hole with different shapes. Rock heterogeneity was also considered in the model in combination with the engineering reality. The combined FEM/DEM approach was first validated by simulating uniaxial compression and Brazilian tests. Then, the parametrical analysis was conducted in detail on the basis of five different sectional shapes of central holes, including a circle, ellipse, U‐shape, trapezoid, and cube, and two lateral pressure coefficients. Analysis of crack propagation paths, released strain energy, displacement, and average velocity distribution of the monitoring points around the central hole suggests that the failure degree and destruction intensity are strongly related to the sectional shape and lateral pressure coefficients. Hard and brittle rock failure induced by the excavation unloading effect can be classified as stable failure (slabbing failure) and unstable failure (strain rockburst). The cubic, trapezoidal, and U‐shaped holes within the specimen are the most likely to induce unstable failure, while stable failure is the dominant failure pattern around circular and elliptical holes. The lateral pressure coefficient λ was also found to affect failure position and intensity (only for the axisymmetric section) around the central hole. The influence of rock heterogeneity on failure intensity and range around the central hole within the specimen was also discussed. This study emphasizes the importance and necessity of the excavation unloading effect when evaluating surrounding rock failure around deep tunnels.https://doi.org/10.1002/ese3.432combined FEM/DEM approachcrack propagationexcavation unloadingfailure characteristicshard rock specimenhole sectional shape |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Fan Feng Shaojie Chen Diyuan Li Songtao Hu Wanpeng Huang Bo Li |
spellingShingle |
Fan Feng Shaojie Chen Diyuan Li Songtao Hu Wanpeng Huang Bo Li Analysis of fractures of a hard rock specimen via unloading of central hole with different sectional shapes Energy Science & Engineering combined FEM/DEM approach crack propagation excavation unloading failure characteristics hard rock specimen hole sectional shape |
author_facet |
Fan Feng Shaojie Chen Diyuan Li Songtao Hu Wanpeng Huang Bo Li |
author_sort |
Fan Feng |
title |
Analysis of fractures of a hard rock specimen via unloading of central hole with different sectional shapes |
title_short |
Analysis of fractures of a hard rock specimen via unloading of central hole with different sectional shapes |
title_full |
Analysis of fractures of a hard rock specimen via unloading of central hole with different sectional shapes |
title_fullStr |
Analysis of fractures of a hard rock specimen via unloading of central hole with different sectional shapes |
title_full_unstemmed |
Analysis of fractures of a hard rock specimen via unloading of central hole with different sectional shapes |
title_sort |
analysis of fractures of a hard rock specimen via unloading of central hole with different sectional shapes |
publisher |
Wiley |
series |
Energy Science & Engineering |
issn |
2050-0505 |
publishDate |
2019-12-01 |
description |
Abstract Hard rock failure and rockburst hazards under high in situ stresses have been the subject of deep rock mechanics and engineering. Previous investigations employed cubic rock specimens with a central hole for simulation of rock fracturing around deep tunnels at a laboratory scale, while the failure characteristics and crack evolution behavior around different shapes of holes induced by excavation unloading response have been barely considered. A commercially combined finite‐discrete element method (combined FEM/DEM) was used to investigate the failure characteristics and crack propagation process of typical hard rock specimens (marble) via the unloading of central hole with different shapes. Rock heterogeneity was also considered in the model in combination with the engineering reality. The combined FEM/DEM approach was first validated by simulating uniaxial compression and Brazilian tests. Then, the parametrical analysis was conducted in detail on the basis of five different sectional shapes of central holes, including a circle, ellipse, U‐shape, trapezoid, and cube, and two lateral pressure coefficients. Analysis of crack propagation paths, released strain energy, displacement, and average velocity distribution of the monitoring points around the central hole suggests that the failure degree and destruction intensity are strongly related to the sectional shape and lateral pressure coefficients. Hard and brittle rock failure induced by the excavation unloading effect can be classified as stable failure (slabbing failure) and unstable failure (strain rockburst). The cubic, trapezoidal, and U‐shaped holes within the specimen are the most likely to induce unstable failure, while stable failure is the dominant failure pattern around circular and elliptical holes. The lateral pressure coefficient λ was also found to affect failure position and intensity (only for the axisymmetric section) around the central hole. The influence of rock heterogeneity on failure intensity and range around the central hole within the specimen was also discussed. This study emphasizes the importance and necessity of the excavation unloading effect when evaluating surrounding rock failure around deep tunnels. |
topic |
combined FEM/DEM approach crack propagation excavation unloading failure characteristics hard rock specimen hole sectional shape |
url |
https://doi.org/10.1002/ese3.432 |
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