摘要
通过开展恒定法向刚度边界条件下三维粗糙节理面循环剪切试验,揭示法向刚度(0~7GPa/m)和循环剪切次数(1~10次)对节理面剪切应力、法向变形、法向应力、剪切应力路径、表面阻力指数、声发射响应和表面磨损特征的影响。试验结果表明:剪切应力-剪切位移路径具有典型的刚度依赖特征,当法向刚度较小时,剪切应力在初始峰值之后逐渐减小,呈现应力软化行为;随着法向刚度的增加,法向位移增加幅度逐渐减小,而由剪切引起的剪切应力与法向应力增加幅度均逐渐变大,呈现应力硬化特征。当循环次数=1时,随着法向刚度由3GPa/m增加至7GPa/m,节理面表观黏聚力和表观内摩擦角分别增加了22.40%和26.84%,而表面阻力指数基本保持稳定。随着循环次数的增加,初始剪切应力峰值逐渐降低,且降低幅度逐渐变缓并最终趋于稳定,其中在循环次数从1增加到2时,初始剪切应力峰值降低幅度最大(24.93%~60.91%);循环剪切过程中,由于节理表面凸起被磨损剪断并趋于光滑,剪胀变形及法向应力增加幅度均逐渐降低;当剪切位移较大时,与法向应力相比,剪切应力增加幅度衰减更为敏感,表面阻力指数逐渐增加。累积声发射能量随着循环次数的增加逐渐减小,而随着法向刚度从0.5 GPa/m增加至7 GPa/m,稳定阶段累积声发射能量增加了229.8%,剪切磨损面积占比增加了72.02%~97.11%。
In this study,the effects of the normal stiffness(0-7 GPa/m) and the number of cyclic shearing(1-10) on the shear stress,normal deformation,normal stress,shear stress path,surface resistance index,acoustic emission responses and surface wear characteristics of joint surfaces were revealed through conducting cyclic shear tests on 3 D rough joint surfaces under constant normal stiffness(CNS) boundary conditions. The experimental results indicate that the shear stress-shear displacement path exhibits typical normal stiffness-dependent characteristics. When the normal stiffness is small,the shear stress declines gradually after the initial peak value,showing a stress softening behavior. With increasing the normal stiffness,the increase extent of the normal displacement declines gradually,while the increase extents of both shear-induced shear stress and normal stress present a gradual increase,characterized by a stress hardening behavior. When the number of cyclic shearing is 1,with an increase of the normal stiffness from 3 GPa/m to 7 GPa/m,the apparent cohesion and apparent internal friction angle of the joint surfaces increase by 22.40% and 26.84%,respectively,while the surface resistance index remains generally stable. With continuous increasing the number of cyclic shearing,the initial peak shear stress declines gradually,while the decrease extent becomes slow down and gradually stabilizes. Especially,the decrease extent of the initial peak shear stress experiences the largest reduction(24.93%-60.91%) with increasing the number of cyclic shearing from 1 to 2. During the cyclic shear process,due to cutting and wearing of the asperities,the joint surfaces tend to be smooth,resulting in gradual reduction of the increase extents of both the dilatancy deformation and the normal stress. When the shear displacement is larger,compared with the normal stress,the attenuation of the increase extent of the shear stress is more sensitive and the surface resistance index increases gradually. The cumulative acoustic emission energy declines with the number of cyclic shearing. However,while the normal stiffness increases from 0.5 GPa/m to 7 GPa/m,the cumulative acoustic emission energy in the stable stage shows an increase by a factor of 2.298,and the ratio of the shear area increases by 72.02%-97.11%.
作者
刘日成
尹乾
杨瀚清
靖洪文
蒋宇静
蔚立元
LIU Richeng;YIN Qian;YANG Hanqing;JING Hongwen;JIANG Yujing;YU Liyuan(State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China;Faculty of Engineering,Nagasaki University,Nagasaki 852-8521,Japan)
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2021年第6期1092-1109,共18页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(51979272,51904290,51734009)。
关键词
岩石力学
恒定法向刚度
循环剪切
节理面
剪胀变形
声发射
二值化
rock mechanics
constant normal stiffness(CNS)
cyclic shear
joint surface
dilatancy
acoustic emission
binaryzation
