岩石材料微裂隙演化的CT识别

 采用砂浆来模拟岩石材料以研究其裂隙的演化规律。借助CT扫描获得单轴压缩破坏过程中岩石材料内部的密度分布信息和统计特征，利用同位置点的密度变化来识别微裂隙的活动，通过统计密度变化特征和分形指标Rd描述研究微裂隙的演化行为。研究结果表明：(1) CT图像灰度频数统计变化曲线的幅值和形状变化反映了微裂隙的不同演化效应：荷载水平0%～50%时，曲线波峰顶点上移，而频数变化幅值显著增大，曲线呈规则正弦状；50%～70%时，曲线波峰顶点下移，频数变化幅值降低，曲线形状偏离正弦状；70%～90%时，曲线形状、波峰顶点位置和频数变化幅值基本不变，只有少数灰度区间发生频数变化；90%以后，曲线波峰顶点位置发生非常大的上移，曲线回归正弦状。而波谷顶点的位置移动则相反。这种现象体现了整个压缩损伤过程中微裂隙的主导演化作用由加载前期萌生效应转化为中期压缩闭合效应，再转化为后期的扩展、汇集效应。(2) 通过对CT图像灰度进行变换及分形指标Rd描述后发现，Rd随应力增加呈先增加→减小→再增加的三段式增长。这与压缩过程中微裂隙的产生效应与闭合效应的相互影响、转化行为有关；加载前期微裂隙的萌生效应活跃，Rd增大；中期萌生效应趋缓，扩展、汇集效应缓慢发展，此时由闭合效应主导，Rd缓慢减小；后期微裂隙的扩展、汇集效应显著增强，Rd急剧增长。(3) 提出的微裂隙体积率分形指标Rd描述能较好地刻画压缩破坏过程中微裂隙演化行为。

CT IDENTIFICATION OF MICROCRACKS EVOLUTION FOR ROCK MATERIALS

The mortar is used to simulated the rock material to study its microcracks evolution laws.The distribution properties and statistical characteristics of density in rock materials are investigated by means of CT scanning during the failure process under uniaxial compression;and the activities of microcracks are reflected by the density varieties of same location in mortar.The evolution behavior of microcracks is studied through the statistical characteristics of density changes and the fractal index Rd.The r...