摘要
对红砂岩进行了蠕变声发射定位试验,分析了声发射震源在沿加载方向与垂直于加载方向上的演化规律。在此基础上,以固定的时间窗口和时间步距,计算并研究了震源zi值与ri值的分形维数特征。试验结果表明:当蠕变应力等于或大于损伤应力时,声发射震源时空演化规律反映的是微裂纹萌生、成核与扩展、贯通的过程。微裂纹的萌生主要产生于减速蠕变阶段,在此过程中微裂纹在沿加载方向与垂直加载方向上,表现为自试件端部与外壁向试件中心演化的过程,并且zi值与ri值的分形维数总体呈现减小的特征。微裂纹的成核过程出现在等速蠕变阶段,其位置位于试件的中心部位。而后,随着蠕变时间的增大,微裂纹步入扩展阶段,此时微裂纹演化表现为自试件中心向端部与外壁方向扩展的过程。对应的zi值与ri值的分形维数均处于较低水平,该特征可作为微裂纹步入成核与扩展过程的标志。微裂纹的贯通产生于加速蠕变阶段,在此过程中沿加载方向上微裂纹主要分布于试件轴向中上部与中下部,而在垂直加载方向上微裂纹遍布试件半径方向,但震源zi值与ri值的分形维数均随着蠕变时间的增大而小幅度上升,该特征可作为微裂纹步入贯通过程的标志。该研究结果可为探索岩石蠕变细观机制与蠕变破坏预测方法提供理论与试验支撑。
The creep acoustic emission(AE)location tests of red sandstone were carried out,and the evolution of AE source along loading direction and perpendicular to loading direction was analyzed.On this basis,the fractal characteristics of source zi value and ri value were studied with fixed time window and time step.The results show that when the creep stress is equal to or greater than the damage stress,the spatio-temporal evolution law of AE source reflects the process of micro-cracks initiation,nucleation,expansion and coalescence.The initiation of micro-cracks mainly occurs in the stage of decelerating creep.During this process,the micro-cracks evolve from the end surfaces and the outer wall to the center of the specimen along the loading direction and the vertical loading direction,and the fractal dimension of zi values and ri values generally decrease.The nucleation process of the micro-cracks appears in the stage of steady creep,and nucleation area locates in the center of the specimen.Then,with the increase of the creep time,the micro-cracks step into the expansion stage,in which the evolution of the micro-cracks is manifested as the expansion process from the center of the specimen to the direction of the end surface and the outer wall,and the fractal dimensions of the corresponding zi values and ri values are at low levels,which can be used as a marker for the process of micro-cracks nucleation and expansion.The coalescence of micro-cracks occurs in the accelerated creep stage.During this process,the micro-cracks are mainly distributed in the axial upper and lower part of the specimen along the loading direction,while in the vertical loading direction,the micro-cracks are distributed all over the radius of the specimen.However,the fractal dimension of source zi value and ri value both increase slightly with the increase of creep time,which can be used as a symbol of micro-cracks coalescing process.The findings in study can provide theoretical and experimental support for exploring rock creep micro-mechanism an
作者
龚囱
赵坤
包涵
赵奎
曾鹏
王文杰
GONG Cong;ZHAO Kun;BAO Han;ZHAO Kui;ZENG Peng;WANG Wen-jie(School of Resources and Environmental Engineering,Jiangxi University of Science and Technology,Ganzhou,Jiangxi 341000,China;Key Laboratory of Ministry of Education for Efficient Mining and Safety of Metal Mine,University of Science and Technology Beijing,Beijing 100083,China)
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2021年第10期2683-2695,共13页
Rock and Soil Mechanics
基金
国家自然科学基金(No.51704128)
中国博士后科学基金(No.2020M671976)
金属矿山高效开采与安全教育部重点实验室开放基金(No.ustbmslab201903)
江西理工大学清江青年英才支持计划(No.JXUSTQJYX2019005)。
关键词
红砂岩
蠕变
损伤强度
声发射震源
分形维数
red sandstone
creep
damage strength
acoustic emission source
fractal dimension
