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。
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.
作者
李杰林
王京瑶
肖益盖
李小双
LI Jielin;WANG Jingyao;XIAO Yigai;LI Xiaoshuang(School of Resources and Safety Engineering,Central South University,Changsha 410083,Hunan,China;State Key Laboratory of Safety and Health for Metal Mines,Maanshan 243000,Anhui,China;School of Civil Engineering,Shaoxing University,Shaoxing 312000,Zhejiang,China)
出处
《黄金科学技术》
CSCD
2023年第1期102-112,共11页
Gold Science and Technology
基金
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”(编号: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”(编号: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”(编号:ZJRMG-2018-Z03)联合资助。
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
stress path
discrete element
damage process
strength criterion
stress tensor
crack propagation
