›› 2018, Vol. 39 ›› Issue (S1): 258-266.doi: 10.16285/j.rsm.2018.0571

• 基础理论与实验研究 • 上一篇    下一篇

半圆盘三点弯曲法测定页岩断裂韧度(KIC) 的实验研究

赵子江1,2,3,刘大安1,2,3,崔振东1,2,3,唐铁吾1,2,3,韩伟歌1,2,3   

  1. 1. 中国科学院地质与地球物理研究所 中国科学院页岩气与地质工程重点实验室,北京100029;2. 中国科学院地球科学研究院,北京100029; 3. 中国科学院大学 地球与行星科学学院,北京100049
  • 收稿日期:2018-04-08 出版日期:2018-07-20 发布日期:2018-09-02
  • 作者简介:赵子江,男,1984年生,博士研究生,主要从事岩石断裂力学和地质工程研究工作。
  • 基金资助:

    国家重点基础研究发展规划(973)项目(No. 2015CB258501);国家自然科学基金项目(No. 41172270);中国科学院战略性先导科技专项(B类)(No. XDB10050201)

Experimental study of determining fracture toughness KIC of shale by semi-disk three-point bending

ZHAO Zi-jiang1,2,3, LIU Da-an1,2,3, CUI Zhen-dong1,2,3, TANG Tie-wu1,2,3, HAN Wei-ge1,2,3   

  1. 1. Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; 2. Institution of Earth Science, Chinese Academy of Sciences, Beijing 100029, China; 3. College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2018-04-08 Online:2018-07-20 Published:2018-09-02
  • Supported by:

    This work was supported by the Youth Project of Major State Basic Research Development Program(2015CB258501), the National Natural Science Foundation of China(41172270); and the Chinese Academy of Sciences Strategic Pilot Project for Science and Technology(Category B)(XDB10050201).

摘要: 为了准确测试页岩的I型断裂韧度KIC,分别采用直切槽半圆盘试样(NSCB)和人字形切槽半圆盘试样(CCNSCB),在3种预制切槽布置模式(splitter、arrester、divider)下,开展三点弯曲加载实验。通过标准差和变异系数分析两类方法KIC测算值的离散性,并评价各自适用性。使用光学显微镜观察试件破裂后的裂纹扩展路径和破裂面断口形态。基于断裂力学理论,给出页岩试件粗糙起伏断口表面能计算公式,分析页岩试件实测值KIC离散的原因,并用最小耗能原理解释裂缝在页岩试件扩展过程中形成粗糙断裂面的机理。对比分析两种试样类型测试的KIC值,认为两种方法在切槽平行层理布置的情况下测算值离散程度一致,二者都适用;对于切槽垂直层理两种布置方式下NSCB试件更容易发生裂缝偏转,导致产生Ⅰ-Ⅱ复合型断裂,使试验失效;CCNSCB试件的韧带具有良好的裂缝扩展导向作用,某种程度上抵消了加载配置非对称性带来的不利影响,CCNSCB比NSCB测得的KIC值离散性更小,更适用于各向异性页岩的KIC测试。

关键词: 页岩, I型断裂韧度, 三点弯曲, CCNSCB和NSCB, 断裂机理

Abstract: In order to accurately test the mode I fracture toughness(KIC) of shale, three point bending loading experiments are carried out using notched semi-circular bend(NSCB) and cracked chevron notched semi-circular bend(CCNSCB) samples under three types of prefabricated notches (splitter, arrester and divider), respectively. According to statistical results of standard deviation and coefficient of variation, discreteness of each group of KIC values is analyzed; and applicability of the two methods is valued respectively. The crack propagation path and fracture surface morphology are observed by optical microscope. Based on fracture mechanics, we give the calculation formulas of the rough undulating fracture surface of shale specimens. The reason for KIC value scattering of the tested shale specimens is analyzed; and the formation mechanism of rough fracture surface in the expansion process is explained using the principle of minimum energy dissipation. By comparing the KIC values of the two sample types, CCNSCB and NSCB methods yield KIC values of similar discreteness when notches are parallel to bedding planes. When notches are vertical to layers, KIC values from CCNSCB specimens is more consistent than that from NSCB. The ligaments of CCNSCB specimens are in favor of crack propagation, which counteracts the adverse influence caused by asymmetry loading configuration to some extent. Therefore, CCNSCB specimens are more suitable to test fracture toughness of anisotropic shale than NSCB.

Key words: shale, mode-I fracture toughness, three-point bending, CCNSCB and NSCB, fracture mechanism

中图分类号: 

  • TU 452

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