岩石应力记忆特性的声发射试验及理论研究

发布时间：2017-12-31 14:41

本文关键词：岩石应力记忆特性的声发射试验及理论研究　出处：《重庆大学》2016年博士论文　论文类型：学位论文

【摘要】：原地应力测量越来越受到地学界和工程界的重视,因为它是人们了解地壳岩石中应力状态最为直接的手段。凯塞效应(Kaiser Effect)测地应力方法因测试成本低、难度小,在国内外普遍受到重视。但是有关Kaiser效应机理及其影响因素的一些问题尚未弄清,例如Kaiser效应的方向性、应力水平、湿度、温度、加工应力等因素对凯塞效应的影响等,特别重要的是岩石试样脱离岩体后,其对应力的记忆性是否随时间推移而削弱或消失对试验结果的准确性影响很大。从岩石脱离岩体至最终加工成型再进行加载试验总是有一定的时间间隔,如果在这一时间间隔内岩对应力的记忆不准确或消失,试验结果将失去意义。纵观现有的研究成果,岩石对先期应力的记忆准确性是否受时间因素影响并无定论,而且均为试验结论,缺少相应的理论解释。本文以砂岩为研究对象,利用WAW-1000型电液伺服试验系统和PCI-2全数字化声发射信号采集系统对轴心受压、三点弯曲和圆盘劈裂试验条件下的声发射特性和信号时频特征进行了较为深入的研究,主要研究内容如下:(1)获得了砂岩单轴压缩、三点弯曲和圆盘劈裂试验下的Kaiser效应时间延迟变化规律。得出了砂岩单轴压缩试验Kaiser效应存在时间延迟,三点弯曲试验Kaiser效应不存在时间延迟,圆盘劈裂试验Kaiser效应是否存在时间延迟并不明确的结论。并拟合出费利西蒂比(Filicity Ratio,FR)与延迟时间的对应公式,对砂岩应力记忆规律进行了量化分析。同时还给出了相应的物理降噪方法。(2)对不同长细比试件的单轴压缩试验,得出圆柱体试件长细比在2.5以内的Kaiser效应比长细比大于2.5明显的结论。对浸水后试件的单轴压缩试验,得出Kaiser效应试件浸水后将不能准确反应先期最大应力(拐点明显)的结论,Kaiser效应与试件的含水率有一定的联系。对花岗岩的单轴压缩试验,得出花岗岩的Kaiser效应不受时间延迟影响的结论。(3)砂岩单轴压缩、三点弯曲和圆盘劈裂试验的三种试验方式,获得的应变曲线与声发射累计振铃数曲线的变化有明显对应关系,表明声发射现象与其裂纹的发展有关。循环加载过程中,砂岩单轴压缩试验的纵向应变竖直段(裂纹压密阶段)和纵向应变斜直线段(裂纹的开展)对应的声发射累计曲线陡增,表明砂岩单轴压缩试验声发射现象与裂纹压密和裂纹再次开展有对应关系;三点弯曲和圆盘劈裂试验的纵向应变曲线上升段(裂纹的开展)对应的声发射累计曲线陡增,表明三点弯曲和圆盘劈裂试验声发射现象与裂纹再次开展有对应关系。(4)对声发射试验波形数据进行时频分析,建立了声发射信号波形的频谱分布与试件内部裂纹变化的对应关系,解释了砂岩应力记忆现象的物理意义。同时编制了运用主次频率差的波形特征搜索方法的Matlab程序,可对Kaiser点进行自动判断,并成功地对单轴压缩的Kaiser点进行了识别。(5)从原裂纹在重复荷载作用下沿原有路径开裂难易程度的角度,建立了砂岩单轴压缩、三点弯曲和圆盘劈裂试验三种试验方式对应的二维力学模型,并对Kaiser效应时间延迟问题作了理论解释,其计算结果与试验结果吻合。同时借助颗粒流软件PFC对Kaiser效应时间延迟进行了再现,得出微裂纹接触面摩擦系数变化和再次加载应力路径变化是Kaiser效应时间延迟诱因的结论。
[Abstract]:In situ stress measurement has attracted more and more academic and engineering circles, because it is for people to understand the crustal rock stress in the most direct way for the state. Kaiser effect (Kaiser Effect) method for measuring initial stress test of low cost, small difficulty, widespread attention at home and abroad. But some problems related factors Kaiser effect mechanism and its effect is not yet known, such as the Kaiser effect direction, stress level, humidity, temperature, working stress and other factors on the Kaiser effect influence, is especially important for the rock samples from rock, the stress of the memory is weaken or disappear over time and affect the accuracy of test results great. From the rock from rock to the final processing and loading test is always a certain time interval, if during this time interval rock stress memory is not accurate or disappear, test. The fruit will lose its meaning. The existing research results, whether the accuracy of memory of early rock stress affected by time is not conclusive, but are lack of test results, the corresponding theoretical explanation. This paper takes sandstone as the research object, the launch of the axial compression signal acquisition system using a WAW-1000 electro-hydraulic servo testing system and PCI-2 digital sound, three point bending and disc splitting test under the condition of acoustic emission characteristics and time-frequency characteristics are studied. The main contents are as follows: (1) the sandstone under uniaxial compression, three point bending and disc splitting time Kaiser effect experiment under delay variation. The sandstone uniaxial compression test of Kaiser effect with time delay, the three point bending test Kaiser effect does not exist time delay, disk split test Kaiser effect whether there is time delay and uncertain conclusion Felicity Be. And fitted (Filicity Ratio, FR) and the corresponding formula of delay time, capacity of memory law of sandstone should be quantified. At the same time, the corresponding physical noise reduction method. (2) the uniaxial compression tests of different slenderness specimens, the cylinder slenderness ratio in the Kaiser effect less than 2.5 of the ratio of slenderness ratio is greater than 2.5. The obvious conclusion of uniaxial compression test specimens obtained after soaking, Kaiser effect of specimen after immersion in water will not accurately reflect the initial maximum stress (inflection point obvious) conclusion, water Kaiser effect and the sample rate of a certain link. The uniaxial compression test the Kaiser effect of granite, granite is not affected by the impact of time delay conclusion. (3) sandstone under uniaxial compression, three test mode splitting test three point bending and disc changes, strain curve and acoustic emission ringing the number curve Ming Significant relationship, show that the development of acoustic emission phenomenon and crack. The cyclic loading process of sandstone, the uniaxial compression test of longitudinal strain in vertical section (crack compaction stage) and longitudinal strain (oblique line segment crack development) corresponding to the acoustic emission cumulative curve sharply, shows that sandstone uniaxial compression test of acoustic emission phenomenon with the crack compaction and crack again carry out corresponding relationship; three point bending and splitting tensile test disc longitudinal strain curves ascent (crack development) corresponding to the acoustic emission cumulative curve shows increased sharply, three point bending and disc splitting test of acoustic emission phenomenon and the corresponding relationship between the cracks carried out again to (4). The time-frequency analysis of the acoustic emission test of waveform data, established the spectrum distribution of AE signal waveform corresponding relationship with the specimens internal crack changes, explains the physical meaning of the sandstone stress memory at the same time for transport With the waveform characteristics of primary and secondary frequency difference search methods Matlab program, can automatically determine the Kaiser point, and successfully to Kaiser under uniaxial compression were identified. (5) from the original crack under repeated loading along the original path of cracking of the degree of difficulty, a sand rock uniaxial compression. Two dimensional mechanical model of three point bending test and disk split three ways of testing the Kaiser effect and the time delay problem have been explained theoretically, and the calculated results agree well with the experimental results. At the same time with the particle flow software PFC on the Kaiser effect of time delay in the reproduction, that micro cracks contact friction coefficient and change again the loading stress path change is the Kaiser effect of time delay causes the conclusion.

【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TU45

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