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岩石Kaiser效应的物理模拟研究

发布时间:2019-05-09 11:11
【摘要】:声发射是一种常见的物理现象,大多数材料发生变形和断裂时都会有声发射现象出现,如一些岩石的破坏等。声发射现象与材料的破坏之间存在着一定的关系。随着科学技术的发展,工程中出现了越来越多的深埋长大隧道,高地应力问题成为了一个不可忽视的问题,研究发现岩石有记录先前所受的历史最高应力的能力,即岩石的Kaiser效应,为准确、便捷的测量地应力提供了一种新的方法。近年来大量的研究人员对声发射进行了大量的研究,取得了许多可喜的成果,但是由于影响声发射现象的因素众多,不同的研究人员得到的结果也不尽相同。本文对砂岩样本进行了单轴压缩实验,利用自主搭建的声发射信号采集系统采集砂岩样本破坏过程中的声发射信号,通过时域分析和频域分析的方法研究砂岩破坏过程中不同破坏阶段的声发射信号特征,建立砂岩破坏过程与声发射现象之间的对应关系。本文还通过采用不同加载速率对砂岩样本进行单轴压缩实验,探讨不同加载速率下砂岩声发射信号的特征。同时本文采用单轴循环加载的方式,模拟岩石近期所受到的历史最大应力,对砂岩的Kaiser效应进行物理模拟研究,第一次加载的范围为0KN-150KN,第二次加载的范围为0KN-290KN,第三次加载的范围为0KN-样本破坏。并绘制不同幅值的荷载-振铃累计曲线判断Kaiser点的位置,对比不同幅值振铃累计曲线所判别的Kaiser点位置的差异,提高Kaiser点的判别精度。通过实验发现:1、采用15KN/s、2.5KN/s加载速率对砂岩加载时,砂岩破坏过程的声发射信号基本可以分为3个阶段,初期阶段、中期阶段和后期阶段,初期阶段有较多的声发射事件发生,中期阶段属于声发射现象的平静期,声发射事件很少,在最后的后期阶段,声发射现象剧烈,过程中出现大量声发射事件2、采用3.5KN/s加载速率加载时,初期阶段和中期阶段划分不明显,整个过程中均有大量声发射事件发生,声发射事件的分布较为均匀。3、砂岩破坏过程中声发射信号频带分布较广,在0-100KHz内均有分布,并且在不同的破坏阶段,声发射信号的频率分布有所不同。4、砂岩在循环加载过程中,在第一次加载的最大荷载150KN附近和第二次加载的最大荷载290KN附近,振铃累计曲线均有明显的转折点即Kaiser点位置,说明砂岩可以记忆先前所受的历史最高应力。5、统计不同幅值的振铃累计曲线得到所确定的Kaiser点的位置存在差异,选择大于2倍和大于10倍的背景噪声幅值的振铃确定Kaiser点位置误差较大,选择大于3倍、4倍、5倍背景噪声幅值的振铃确定的Kaiser点位置精度较高。
[Abstract]:Acoustic emission (AE) is a common physical phenomenon. Most materials will have acoustic emission phenomena when they are deformed and fractured, such as the failure of some rocks. There is a certain relationship between acoustic emission phenomenon and material failure. With the development of science and technology, more and more deep-buried large tunnels have appeared in the engineering, and the problem of high in-situ stress has become a problem that can not be ignored. The study found that the rock has the ability to record the highest stress in history. That is, the Kaiser effect of rock provides a new method for accurate and convenient measurement of in-situ stress. In recent years, a large number of researchers have carried out a lot of research on acoustic emission, and achieved a lot of gratifying results. However, due to the many factors affecting the phenomenon of acoustic emission, the results obtained by different researchers are not always the same. In this paper, the uniaxial compression test of sandstone samples is carried out, and the acoustic emission signals during the failure process of sandstone samples are collected by an acoustic emission signal acquisition system built by itself. The characteristics of AE signals in different failure stages in sandstone failure process are studied by means of time domain analysis and frequency domain analysis, and the corresponding relationship between sandstone failure process and acoustic emission phenomenon is established. Through uniaxial compression experiments on sandstone samples with different loading rates, the characteristics of acoustic emission signals of sandstone under different loading rates are also discussed in this paper. At the same time, the historical maximum stress of rock is simulated by uniaxial cyclic loading, and the Kaiser effect of sandstone is studied by physical simulation. The range of the first loading is 0KN 鈮,

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