单轴加载下红砂岩损伤强度的损伤表征及声发射特性研究

发布时间：2018-08-24 20:24

【摘要】：岩石脆性破坏是个渐进发生的过程,损伤强度是岩石破坏过程中重要的应力门槛值,是岩石压缩过程中不同破坏阶段的分界点,也是裂纹非稳定扩展的起点。为充分了解红砂岩单轴加载下损伤强度损伤与声发射特征,本文通过对红砂岩进行室内声发射试验,分析了声发射累计振铃计数与主频变化规律,探讨了声发射法、裂纹体积应变模型法、损伤统计本构模型法与耗散能法表征红砂岩损伤的适用性与差异性;结合红砂岩损伤强度,研究红砂岩损伤强度声发射变化规律与损伤特征。综合以上研究内容,主要研究结论如下:(1)单轴加载下,基于裂纹应变模型法确定的红砂岩损伤强度与峰值强度的比为0.69~0.85。(2)损伤强度前岩石内部裂纹压密后又重新扩展,声发射累计振铃计数稳定增加,损伤强度以后岩石内部裂纹非稳定扩展,声发射累计振铃计数急剧增加,声发射累计振铃计数急剧增长点在损伤强度以后,声发射急剧增长点比峰值应力的值与损伤强度比峰值应力的值差为0.15~0.3。(3)在初始压密阶段和弹性阶段,声发射主频主要集中在100~350 kHz,损伤强度点后,有大量0~50 kHz和400~500 kHz的声发射信号出现,声发射主频带变宽,主频范围变为0~500 kHz;损伤强度以前,岩石内部裂纹压密与重新扩展,0~160 kHz的低频声发射信号一般不超过加载全程的20%;300~500 kHz的高频声发射信号一般不超过16%。(4)声发射法、裂纹体积应变模型法、损伤统计本构模型法与耗散能法均能较好的表征红砂岩单轴加载损伤规律,四种损伤变量表征的损伤具有高度一致性,损伤强度处,基于声发射法表征的损伤变量值不超过0.2,基于裂纹体积应变模型法表征的损伤变量值不超过0.35,基于损伤统计本构模型法表征的损伤变量值小于0.18,基于耗散能法表征的损伤变量值不超过0.15,基于裂纹体积应变模型法表征的损伤变量要其他3种方法表征的损伤变量。损伤强度前,岩石损伤较小,损伤强度以后损伤急剧增大导致岩石失稳破坏,岩石损伤主要集中在裂纹非稳定扩展阶段。(5)能量耗散主要集中在损伤强度以后的塑性屈服阶段,岩石内部的裂纹扩展贯通,岩石损伤急剧增大。岩石耗散的能量一部分被声发射接收,声发射急剧增多;另一部分能量用于裂纹的急剧扩展与贯通,最终导致岩石失稳破坏。
[Abstract]:Brittle failure of rock is a gradual process. The damage strength is an important stress threshold in the process of rock failure, the boundary point of different failure stages in the process of rock compression, and the starting point of unstable crack propagation. In order to fully understand the damage intensity damage and acoustic emission (AE) characteristics of red sandstone under uniaxial loading, this paper analyzes the accumulative ringing count and main frequency variation of red sandstone by laboratory acoustic emission test, and discusses the acoustic emission method. Crack volume strain model method, damage statistical constitutive model method and dissipative energy method are used to characterize the applicability and difference of red sandstone damage, and combined with the damage intensity of red sandstone, the changes of damage intensity and damage characteristics of red sandstone are studied. The main conclusions are as follows: (1) under uniaxial loading, the ratio of damage strength to peak strength of red sandstone determined by the method of crack strain model is 0.69 ~ 0.85. The accumulative ringing count of acoustic emission increases steadily, the internal crack of rock expands unsteadily after the damage intensity, the accumulative ring count of acoustic emission increases sharply, and the sharp growth point of accumulative ring count of acoustic emission increases after the damage intensity. The difference between the value of peak stress and the ratio of damage intensity to peak stress of sharp growth point of acoustic emission is 0.15 ~ 0.30.3.In the initial compaction stage and elastic stage, the main frequency of acoustic emission is mainly concentrated after the damage intensity point of 100 ~ 350 kHz,. A large number of acoustic emission signals of 0 ~ 50 kHz and 400 ~ 500 kHz appeared, the main frequency band of acoustic emission became wider, and the main frequency range changed to 0 ~ 500 kHz; damage intensity. The low frequency acoustic emission (LOAE) signals of the internal crack compaction and repropagation of a rock are generally not more than that of the full loading range of 20, 300 and 500 kHz. (4) the acoustic emission method, the crack volume strain model method, are generally not more than 16 parts. The damage statistical constitutive model method and dissipative energy method can well characterize the damage law of red sandstone under uniaxial loading. The damage variable value based on acoustic emission method is not more than 0.2, the damage variable value based on crack volume strain model method is not more than 0.35, the damage variable value based on damage statistical constitutive model method is less than 0.18, and the damage variable value based on dissipative energy method table. The damage variable value is not more than 0.15. The damage variable based on the crack volumetric strain model is the damage variable characterized by the other three methods. Before the damage intensity, the rock damage is small, and the damage increases sharply after the damage strength, which leads to the rock instability failure, and the rock damage is mainly concentrated in the stage of the crack unsteady growth. (5) the energy dissipation is mainly concentrated in the plastic yield stage after the damage strength. Crack propagation through the rock leads to a sharp increase in rock damage. Some of the dissipated energy of rock is received by acoustic emission, and the other part of energy is used for crack propagation and penetration, which leads to rock instability and failure.
【学位授予单位】：江西理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD315

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