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黄金科学技术 ›› 2023, Vol. 31 ›› Issue (1): 102-112.doi: 10.11872/j.issn.1005-2518.2023.01.101

• 采选技术与矿山管理 • 上一篇    下一篇

不同应力路径下岩石细观力学性能离散元研究

李杰林1,2(),王京瑶1,肖益盖1,2,李小双3   

  1. 1.中南大学资源与安全工程学院,湖南 长沙 410083
    2.金属矿山安全与健康国家重点实验室,安徽 马鞍山 243000
    3.绍兴文理学院土木工程学院,浙江 绍兴 312000
  • 收稿日期:2022-08-10 修回日期:2022-10-19 出版日期:2023-02-28 发布日期:2023-03-27
  • 作者简介:李杰林(1982-),男,湖南宁远人,博士,副教授,从事采矿工程与岩石力学研究工作。lijielin@163.com
  • 基金资助:
    湖南省自然科学基金项目“寒区冻融循环作用下裂隙岩体损伤局部化效应研究”(2020JJ4712);金属矿山安全与健康国家重点实验室开放课题“深部高应力巷道围岩结构面与危险块体自动识别方法研究”(2020-JSKSSYS-06);浙江省岩石力学与地质灾害重点实验室开放研究基金项目“深部高应力硬岩开挖卸荷的时变力学特性及其变形破裂机理”(ZJRMG-2018-Z03)

Research on Meso-mechanical Properties of Rock Under Different Stress Paths Based on Discrete Element Method

Jielin LI1,2(),Jingyao WANG1,Yigai XIAO1,2,Xiaoshuang LI3   

  1. 1.School of Resources and Safety Engineering, Central South University, Changsha 410083, Hunan, China
    2.State Key Laboratory of Safety and Health for Metal Mines, Maanshan 243000, Anhui, China
    3.School of Civil Engineering, Shaoxing University, Shaoxing 312000, Zhejiang, China
  • Received:2022-08-10 Revised:2022-10-19 Online:2023-02-28 Published:2023-03-27

摘要:

岩体工程中的应力状态对围岩的稳定性具有重要影响。为研究地下巷道中岩体应力状态对围岩稳定性的影响规律,基于离散元理论,对地下巷道开挖过程的应力状态进行分析,开展了围压卸载—轴压增加、围压卸载—轴压不变和围压卸载—轴压减少3种不同卸载路径下的三轴压缩数值模拟试验,并与常规三轴压缩试验进行对比,分析了不同应力路径下的岩石宏观强度特征及细观损伤过程差异性。结果表明:强度准则和应力张量状态不受卸载路径的影响,但不同应力路径下岩体的损伤过程不同,围压卸载—轴压不变应力路径下的微观裂纹发育最密集,而围压卸载—轴压增加应力路径下的裂纹丛集速度最快。研究结果可为地下巷道开挖过程中的围岩应力卸载破坏分析提供参考。

关键词: 应力路径, 离散元, 损伤过程, 强度准则, 应力张量, 裂纹扩展

Abstract:

The stress state of rock mass in engineering has an important influence on the stability of surrounding rock.At present,scholars at home and abroad mainly study the deformation and failure of rock during loading and unloading through rock mechanics tests such as uniaxial compression and conventional triaxial compression.However,in the process of excavation,the stress state of the rock mass in the radial direction is unloaded and the axial direction is loaded,which is more in line with the actual working conditions.Therefore,the results obtained by traditional research methods can’t truly reflect the stress state of rock mass.There are still some limitations to reflect the stress unloading effect and mechanical characteristics of rock excavation in underground engineering by laboratory test.Moreover,due to the differences of test conditions and rock types,the initial damage degree in the process of rock sample processing is different,the load control methods in the test are different and the number of repeated samples is small,which leads to the dispersion error of test results larger than the true range of stress path’s influence on strength.In order to study the influence of stress state on the stability of surrounding rock in rock mass engineering,based on the discrete element theory,the stress state in the process of underground roadway excavation was analyzed,and triaxial compression numerical simulation tests under three different unloading paths,i.e. confining pressure unloading-axial pressure increasing,confining pressure unloading-axial pressure unchanged and confining pressure unloading-axial pressure decreasing,were carried out.Compared with conventional triaxial compression tests,the macroscopic strength characteristics and microscopic damage process differences of rocks under different stress paths were analyzed.The results show that with the increase of confining pressure,the macroscopic crack of rock changes from tensile crack under uniaxial compression to single inclined plane shear crack under low confining pressure,and finally the conjugate crack shape appears under high confining pressure,which indicates that confining pressure is an important factor affecting the crack state of rock.The failure of the same rock under different unloading paths also follows Hoek-Brown strength criterion,that is,different stress paths will not affect the ultimate strength of the rock.The aggregation characteristics of contact force vector projection scatterplots under different unloading paths are similar,so the stress tensor state is not affected by unloading paths,but the damage process is different under different stress paths.Micro-cracks develop most intensively under the stress path of confining pressure and unloading-constant axial pressure.The crack cluster speed is the fastest under the stress path of confining pressure unloading and axial pressure increasing.The research results can provide reference for stress unloading failure analysis of surrounding rock in the process of underground roadway excavation.

Key words: stress path, discrete element, damage process, strength criterion, stress tensor, crack propagation

中图分类号: 

  • TD853

图1

地下巷道卸载过程中围岩应力变化情况"

图2

巷道开挖过程4种应力路径方案"

图3

常规三轴压缩试验方案"

图4

卸载应力路径试验方案"

表1

离散元细观参数取值"

参数名称数值参数名称数值
模型宽度/mm50颗粒刚度比1.5
模型高度/mm100颗粒阻尼系数0.5
颗粒半径/mm1.00~1.66拉伸强度/MPa30
密度/(kg·m-32 500内聚力/MPa30
孔隙度0.1黏结摩擦角/(°)30
摩擦系数0.5黏结有效模量/GPa13.0
有效模量/GPa13.0黏结刚度比6.0

图5

20 MPa围压下砂岩试样的标定结果注:图5(b)为颗粒破坏后的fragment显示,其中同种颜色的颗粒代表相同破碎块体"

图6

常规三轴离散元试验宏观裂纹"

图7

常规三轴离散元试验应力—应变曲线"

图8

GHB准则拟合结果"

图9

围压卸载—轴压不变应力路径下位移、应力及裂纹扩展状况"

图10

围压卸载—轴压增加应力路径下位移、应力及裂纹扩展状况"

图11

围压卸载—轴压减少应力路径下位移、应力及裂纹扩展状况"

图12

法向接触力矢量散点图(a)加载路径对照组;(b)围压卸载—轴压增加;(c)围压卸载—轴压不变;(d)围压卸载—轴压减少"

图13

切向接触力矢量散点图(a)加载路径对照组;(b)围压卸载—轴压增加;(c)围压卸载—轴压不变;(d)围压卸载—轴压减少"

图14

不同应力路径下岩样的裂纹数量及裂纹倾角分布"

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