单轴加载条件下花岗岩声发射及波传播特性研究

发布时间：2018-05-15 13:37

本文选题：岩石力学 + 单轴压缩　；参考：《岩石力学与工程学报》2017年05期

【摘要】：采用声波、声发射一体化装置,研究单轴压缩下花岗岩波速与声发射演化规律,通过宏细观方法确定各应力门槛值,研究裂纹扩展不同阶段声发射演化及波传播规律。结果表明:细观裂纹的演化与宏观变形直接对应,由于微裂纹主要沿轴向扩展,导致轴向刚度对裂纹起裂及贯通的敏感度弱于非线性增长的侧向变形,瞬时泊松比曲线斜率变化点与应力门槛值对应,声发射测试确定的起裂应力比宏观应变法偏小,但反映了微裂纹的初始萌生;采用实测波速变化分析声发射震源的时空及幅值演化分布,较好地描绘了裂纹的扩展过程,由于不同阶段声发射信号的幅值及能量存在差异,导致声发射特征参数演化规律差异较大(尤其在损伤应力之后),AE能量在破坏前呈突发性增长,可作为灾害性破坏的前兆;加载初始阶段,由于微裂隙的闭合,波速及波幅均随应力逐渐增大,但增加速率逐渐下降,侧向波速在闭合应力附近基本达到峰值,此后一定阶段基本保持不变,但其他方向波速则继续增大,随着波传播方向与径向夹角的增大,波速增加幅度及波速下降点对应的应力(损伤应力前、后)逐渐增大,峰值应力附近对应波速下降幅度减小;波速受损伤演化的影响要滞后于声发射事件。
[Abstract]:The acoustic wave velocity and acoustic emission evolution law of granite under uniaxial compression are studied by means of acoustic wave and acoustic emission integrated device. The stress threshold values are determined by macroscopical method, and the acoustic emission evolution and wave propagation in different stages of crack propagation are studied. The results show that the evolution of microcracks corresponds directly to the macroscopic deformation. Because the microcracks are mainly propagated along the axial direction, the sensitivity of axial stiffness to crack initiation and penetration is weaker than that of nonlinear lateral deformation. The slope change point of the instantaneous Poisson's ratio curve corresponds to the stress threshold. The initial crack stress determined by acoustic emission test is smaller than that determined by macroscopic strain method, but it reflects the initial initiation of microcracks. The time-space and amplitude evolution distribution of acoustic emission source is analyzed by using the measured wave velocity variation, and the crack propagation process is well described. Due to the difference of amplitude and energy of acoustic emission signal in different stages, As a result, the evolution law of acoustic emission characteristic parameters is different (especially after the damage stress, the energy of AE increases suddenly before failure, which can be used as a precursor of disastrous damage, and at the initial stage of loading, because of the closure of microfracture, the energy of AE increases suddenly before failure. The wave velocity and amplitude increase gradually with the stress, but the increasing rate decreases gradually, and the lateral wave velocity reaches the peak value near the closed stress, after which the wave velocity remains basically unchanged, but the other directional wave velocities continue to increase. With the increase of the angle between the direction of wave propagation and the radial angle, the amplitude of wave velocity increase and the stress corresponding to the drop point of wave velocity (before and after the damage stress) increases gradually, and the corresponding amplitude of wave velocity decreases near the peak stress. The influence of damage evolution on wave velocities lags behind acoustic emission events.
【作者单位】：中国科学院武汉岩土力学研究所岩土力学与工程国家重点实验室;南京理工大学机械工程学院;
【基金】：国家自然科学基金重点项目(51439008);国家自然科学基金面上项目(41572307);国家自然科学基金青年科学基金项目(51209200)~~
【分类号】：TU45

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