不同加载路径对岩石Kaiser效应影响的试验研究

发布时间：2019-03-14 11:45

【摘要】：使用岩石Kaiser效应方法来测量原岩地应力,具有便捷、经济的优点,近年来被广泛研究和使用。但是,目前该方法还存在一些尚未解决的技术问题,其中之一就是:在钻取岩芯以便通过室内Kaiser效应试验来测量地应力时,在所钻取的岩芯的轴线方向与现场主应力的主方向不一致(即,初次加载方向与后续加载方向不一致)的条件下,Kaiser效应是否存在,能否获得正确的结果。本文采用花岗岩试样进行室内试验,研究了单轴加载条件下初始加载方向与后续加载方向之间存在一定夹角时,夹角大小对Kaiser效应的存在与否以及夹角对Kaiser点判断的影响的研究。同时,还进行了三轴加载条件下不同预加载路径对Kaiser效应影响的研究。所获主要结论如下:1.在初次加载应力处于远低于试样强度的30%低应力水平的条件下,当声发射信号很少时,会出现Kaiser效应不显著情况。在这样的情况下,以能量计数和振铃计数第一次开始持续增加时对应的应力水平平均值作为Kaiser点,比较准确。2.在初次加载应力达到较高应力水平(大体接近试样强度的65%)的条件下,当第二次加载应力还未达到先前最大应力时,声发射信号就变得活跃,以累计能量计数和累计振铃计数曲线的拐点后出现的第一个曲率增大点对应的应力水平平均值作为Kaiser点,误差较小。3.三轴加载试验得到:①.在先加围压后加轴压条件下,第二次单轴加载出现的Kaiser点对应的应力对之前所预加载的轴压有很好的记忆性。即,此时围压对Kaiser效应没有影响。②.先加轴压后加围压条件下,Kaiser效应不显现。③.在三向等压加载下条件,Kaiser效应不显现。4.单轴加载后,后续加载方向分别改变15°和20°试验得到:在进行第二次加载时,都能够观察到显著的Kaiser效应;但对之前受到最大应力的记忆是提前的;且对后续加载方向改变15°和20°的情形,FR值分别为0.76和0.71。
[Abstract]:It is convenient and economical to use the method of rock Kaiser effect to measure the in-situ stress of the original rock, which has been widely studied and used in recent years. However, there are still some unsolved technical problems in this method. One of them is that when drilling the core to measure the in-situ stress through indoor Kaiser effect test, Under the condition that the axis direction of the core drilled is not consistent with the principal direction of the field principal stress (that is, the direction of initial loading and the direction of subsequent loading), whether the Kaiser effect exists or not and whether the correct results can be obtained. In this paper, the granite samples are tested in laboratory, and the angle between the initial loading direction and the subsequent loading direction under uniaxial loading is studied. The influence of angle size on the existence of Kaiser effect and the influence of angle on Kaiser point judgment are studied. At the same time, the influence of different preloading paths on Kaiser effect under triaxial loading is also studied. The main conclusions obtained are as follows: 1. Under the condition that the initial loading stress is much lower than the 30% low stress level of the specimen strength, when the acoustic emission signal is very little, the Kaiser effect will not be significant. In this case, the average stress level corresponding to the first continuous increase of the energy count and ring count is used as the Kaiser point, which is more accurate. Under the condition that the initial loading stress reaches a higher stress level (approximately 65% of the specimen strength), the acoustic emission signal becomes active when the second loading stress does not reach the previous maximum stress. Taking the average stress level corresponding to the first curvature increase point after the inflection point of cumulative energy count and cumulative ring counting curve as the Kaiser point, the error is small. 3. The results of triaxial loading test are as follows: 1. Under the condition of first confining pressure followed by axial compression, the stress corresponding to the Kaiser point in the second uniaxial loading has a good memory for the pre-loaded axial compression. That is, at this time the confining pressure has no effect on the Kaiser effect. Under the condition of axial compression first and confining pressure, the Kaiser effect does not show up. 3. Under the condition of three-way isobaric loading, the Kaiser effect does not appear. 4. After uniaxial loading, the direction of subsequent loading was changed by 15 掳and 20 掳, respectively. The results showed that the significant Kaiser effect could be observed during the second loading, but the memory of the maximum stress before loading was earlier. When the direction of subsequent loading is changed by 15 掳and 20 掳, the FR values are 0.76 and 0.71 respectively.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD315

【参考文献】