单轴受载下岩体破裂演化特征的声发射CT成像

 岩石受载下的内部破裂演化特征对于研究岩石破坏机制具有重要意义。将声发射(AE)与CT成像技术相结合，对3种不同加载速率下的泥岩试样进行声发射CT反演计算，分析各加载阶段波速分布特征，探究波速演化与岩样宏、微观破裂的关系。研究结果表明：(1) 在加载初期，岩样内部波速范围变化较小，波速异常区面积较小且分布较为零散；随着载荷增加，波速范围不断增加，同时波速异常区面积也在不断扩大；临近破坏阶段，波速范围进一步增加，其低波速区也逐渐形成大面积贯通。(2) 岩样实际宏观破裂位置与低波速区及波速异常丰富区位置吻合，说明临近破坏阶段，岩样内部微裂隙的大量萌生发育使低波速区快速扩展贯通，同时微裂隙周围的岩石颗粒因受挤压而呈现出高波速状态。(3) 受载初期，岩样内初始微裂隙发育萌生位置与低波速区大致吻合；随载荷增加，大量微裂隙开始在低波速区与波速异常丰富区聚集、延伸；在临近破坏阶段，微破裂密集区扩展贯通，其所处区域与岩样破裂位置大体一致。(4) 反演计算调整前后的AE事件整体分布特征保持一致，证明了初始AE事件定位的准确性及声发射CT成像的可靠性。

Evolution characteristics of rock fracture under uniaxial loading by combining acoustic emission and CT imaging

Characteristics of fracture evolution inner loaded rock are significant for understanding rock failure mechanism. In this paper，acoustic emission(AE) and CT imaging techniques were combined to perform CT inversing calculation for mudstone samples in different loading speeds， the characteristics of velocity distribution in rocks in different loading phases were analyzed，and relations between velocity evolution and macro- and micro-fractures of rocks were studied. The results show that：(1) In initial loading phase，the variation of velocity scale in rock samples is minor，and the velocity anomalies regions are small and distributed scatteredly. When loading increases，the velocity scale grows and the velocity anomalies regions are enlarging continuously. Before failure，the velocity scale further increases and large areas of low velocity regions connect mutually. (2) The macrofractures position in rock samples after failure has a positive corresponding relation with the region of low wave velocity and affluent wave velocity anomalies，indicating that when approaching failure，numbers of sprouting and growing microfractures lead to rapid expansion and connection of low velocity regions，and the regions of particles around microfractures represent high velocity status caused by compression；(3) In initial loading phases，locations of the emerging micro-fractures correlate well with low velocity regions. When loading increases，numbers of microfractures sprout in the regions of low velocities and affluent velocity anomalies. Before failure，dense areas of microfractures expand and connect，which correspond with the macrofracutres of rock samples. (4) There is a similar AE events distribution before and after inversing calculation，which proves the accuracy of the initial AE locations and the reliability of CT imaging results.