崔振东, 李晓, 刘大安, 王博楠, 韩伟歌, 张建勇, 王燚钊. 2018: 页岩微纳观尺度雁列式断续裂纹的原位观测. 工程地质学报, 26(1): 85-90. DOI: 10.13544/j.cnki.jeg.2018.01.009
    引用本文: 崔振东, 李晓, 刘大安, 王博楠, 韩伟歌, 张建勇, 王燚钊. 2018: 页岩微纳观尺度雁列式断续裂纹的原位观测. 工程地质学报, 26(1): 85-90. DOI: 10.13544/j.cnki.jeg.2018.01.009
    CUI Zhendong, LI Xiao, LIU Da'an, WANG Bonan, HAN Weige, ZHANG Jianyong, WANG Yizhao. 2018: IN-SITU OBSERVATION OF EN ECHELON INTERMITTENT CRACKS OF SHALE IN MICRO-NANO SCALE. JOURNAL OF ENGINEERING GEOLOGY, 26(1): 85-90. DOI: 10.13544/j.cnki.jeg.2018.01.009
    Citation: CUI Zhendong, LI Xiao, LIU Da'an, WANG Bonan, HAN Weige, ZHANG Jianyong, WANG Yizhao. 2018: IN-SITU OBSERVATION OF EN ECHELON INTERMITTENT CRACKS OF SHALE IN MICRO-NANO SCALE. JOURNAL OF ENGINEERING GEOLOGY, 26(1): 85-90. DOI: 10.13544/j.cnki.jeg.2018.01.009

    页岩微纳观尺度雁列式断续裂纹的原位观测

    IN-SITU OBSERVATION OF EN ECHELON INTERMITTENT CRACKS OF SHALE IN MICRO-NANO SCALE

    • 摘要: 在自然界岩石和工程围岩中,宏观尺度雁列式断续破裂现象较为常见。然而,在微纳观尺度上,是否也存在类似的雁列式断续破裂特征?其扩展与演化过程又是怎样的?这是非常值得探讨的基础科学问题。采用带切槽的弧形页岩试样,在扫描电子显微镜(SEM)下开展原位拉伸与微纳观破裂过程观测试验。基于原位观测分析,获得如下几点认识:(1)在微纳米尺度,依然存在断续破裂现象,呈“S”形或反“S”形雁列式展布,是由裂纹尖端部位拉张-剪切复合应力场及矿物非均质性共同诱导形成的。(2)微纳观雁列式断续裂纹总体展布特征和扩展、演化过程是有规律可循的,相邻微裂纹近似平行展布。对单个裂纹来讲,中间的拉张裂纹近似平行于最大拉张应力方向,而两端翼裂纹转向朝着最大剪切应力方向扩展。(3)微纳观雁列式断续裂纹仅代表着主裂纹路径形成过程中的暂时的剪切变形状态或某个中间扩展阶段。(4)雁列式断续裂纹在微米至纳米尺度上具有多尺度分层级结构特征:相对较大尺度的雁列式断续裂纹包含着更小尺度的次级雁列式断续裂纹。该研究提供了微纳观尺度页岩雁列式破裂的观测证据,为分析页岩多尺度裂纹演化过程提供了重要支撑。

       

      Abstract: In macroscopic scale, en echelon intermittent fractures are common in nature and in engineering rocks. Nevertheless, do these en echelon intermittent fractures still occur in micro-nano scale? What is the specific process of crack growth and evolution? This is a basic scientific problem for rock mechanics. Using the arch specimens of shale with a notch on the arch boundary, in-situ tension and crack growth observation are conducted under a scanning electron microscope(SEM). from the in-situ SEM observations, we learn that:(1)En echelon intermittent cracks still can be observed in micro-nano scale with a "S" or reversed "S" shape. They are induced by combined actions of complex tension-shear stress field ahead of the crack tip and the mineral anisotropy.(2)the arrangements, growth and evolution process of these en echelon intermittent cracks generally follow a certain regularity. the adjacent intermittent cracks are approximately parallel to each other. for each single crack, the intermediate tensile crack is parallel to the maximum tension stress, and the wing cracks at both ends tend to grow towards the maximum shear stress.(3)En echelon intermittent cracks in micro-nano scale only represent a transient state of shearing deformation or an intermediate growth stage of the main crack.(4)There exists a hierarchical structure among some en echelon intermittent cracks in micro-nano scale. the en echelon intermittent cracks in relatively large scale are included in those in relatively small scale. This paper provides observation evidence for en echelon intermittent cracks, which contributes for analysis on the evolution process of multi-scale cracks.

       

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