热损伤花岗岩三轴压缩蠕变破坏声发射及损伤演化特征  

Creep acoustic emission and damage evolution of thermally-damaged granite under triaxial stress

作　　者：周露林 刘建锋[1,2] 鲁功达 梁超[1,2] 林浩 ZHOU Lulin;LIU Jianfeng;LU Gongda;LIANG Chao;LIN Hao(State Key Laboratory of Hydraulic and Mountain River Engineering,Sichuan University,Chengdu 610065,China;College of Water Resources and Hydropower,Sichuan University,Chengdu 610065,China)

机构地区：[1]四川大学水力学与山区河流开发保护国家重点实验室,四川成都610065 [2]四川大学水利水电学院,四川成都610065

出　　处：《中南大学学报（自然科学版）》2023年第6期2360-2369,共10页Journal of Central South University:Science and Technology

基　　金：四川省重点研发资助项目(2022YFSY0007)。

摘　　要：为探究深部高温高压环境对工程围岩蠕变性质的影响,开展了不同程度热损伤花岗岩的三轴分级蠕变加载试验,分析其声发射活动及损伤演化特征。研究结果表明:在分级蠕变加载中,当轴向应力达到1.50~1.65倍损伤应力σ_(cd)后,花岗岩损伤演化加快,达到(1.65~1.80)σ_(cd)后,发生加速蠕变破坏;在同一级加载中,随热处理温度升高,声发射活动在减速蠕变和稳态蠕变阶段减弱,在加速蠕变阶段增强;围压效应可以减弱热损伤对花岗岩蠕变特性的影响,围压与热损伤的耦合效应可以抑制蠕变过程的裂纹扩展,但当轴向应力增大、岩石失稳后热损伤对蠕变破坏加剧起控制作用;在分级加载过程中,随热处理温度升高,损伤变量的增长趋势先减缓后加快,600℃热处理试样损伤发展最快,常温试样次之,150℃和300℃热处理试样最慢;蠕变过程中剪切裂纹占比在35%~60%,随分级加载应力增大,微裂纹类型向剪切型转化;热损伤花岗岩矿物晶粒内和晶界裂纹有不同程度的发育,导致剪切裂纹占比随热处理温度升高而先减小后增大。In order to investigate the influence of high in-situ stress and high temperature on the creep properties of engineering surrounding rocks,a series of stress-stepping creep experiments were carried out on thermally-damaged granite samples.The staging characteristics of acoustic emission(AE)activity and damage evolution were analyzed.The results show that when the axial stress reaches(1.50-1.65)σcd(the crack damage stress)during stress stepping,the creep damage evolution of granite accelerates.When the axial stress reaches(1.65-1.80)σ_(cd),the accelerated creep stage occurs.With the increase of temperature,the AE ringing counts and energy first decrease in the attenuation creep stage and steady-state creep stage,and then increase in the accelerated creep stage.Confining pressure reduces the effect of thermal damage on granite creep properties,and the coupled effects of thermal damage and hydrostatic compaction inhibit the cracking process.However,when the axial stress increases and the structural stability begins to weaken,thermal damage would accelerate the creep failure.During the graded loading process,the trend of damage variable evolution first slows down and then accelerates with the increase of temperature.The damage evolution of samples thermally damaged at 150℃and 300℃is the slowest,while it is the fastest at 600℃.With the increase of axial stress,the proportion of shear crack increases in the range of 35%-60%.Thermal damage induces intergranular and transgranular cracks in granite minerals,resulting in decrease first and then increase of the proportion of shear cracks with the increase of temperature.

关 键 词：花岗岩 热损伤 蠕变 声发射 损伤变量 R_(A)与F_(A) 

分 类 号：TU457[建筑科学—岩土工程]