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李 震,吴冠洋,司尚金,等. 层状岩石逆倾向与顺倾向剪切破坏特征的差异性研究[J]. 煤炭科学技术,2024,52(7):37−47. doi: 10.12438/cst.2024-0222
引用本文: 李 震,吴冠洋,司尚金,等. 层状岩石逆倾向与顺倾向剪切破坏特征的差异性研究[J]. 煤炭科学技术,2024,52(7):37−47. doi: 10.12438/cst.2024-0222
LI Zhen,WU Guanyang,SI Shangjin,et al. Differences between reverse and normal shear in failure characteristics of layered rocks[J]. Coal Science and Technology,2024,52(7):37−47. doi: 10.12438/cst.2024-0222
Citation: LI Zhen,WU Guanyang,SI Shangjin,et al. Differences between reverse and normal shear in failure characteristics of layered rocks[J]. Coal Science and Technology,2024,52(7):37−47. doi: 10.12438/cst.2024-0222

层状岩石逆倾向与顺倾向剪切破坏特征的差异性研究

Differences between reverse and normal shear in failure characteristics of layered rocks

  • 摘要: 层状岩石层理效应的研究对深部岩体稳定性分析具有重要意义,而天然层状岩石逆倾向与顺倾向剪切力学行为差异性仍认识不清。为此,开展了0°≤ψ≤180°(ψ为剪切面顺时针旋转至层理面的滑动倾向角)的页岩全角度剪切试验,详细地研究了逆倾向与顺倾向下剪切力学特性和破坏模式的差异性,并结合离散元模拟进行了补充分析与验证。研究结果表明:顺层面剪切时抗剪强度取得最小值,ψ=30°时取得最大值,90°与135°时取得局部极大值,逆倾向抗剪强度相对更高,ψ>30°时随滑动倾向角增加抗剪强度总体呈减小趋势;根据不同滑动倾向角下剪切力学行为的差异性,按滑动倾向角将层状岩石分为三组,即层面张拉与基质剪切组(15°~60°)、基质剪切组(75°~120°)、基质与层面剪切组(135°~180°);基质剪切组在剪切应力−位移曲线峰前均存在应力降现象,层面张拉与基质剪切组在峰后呈“阶梯”状应力降低;张拉破坏与剪切破坏同时存在且以剪切破坏为主;顺层面剪切时层面的剪切裂纹数目占优,ψ=90°时基质体的剪切裂纹数目最多,ψ=30°时层面的张拉裂纹数目最多,其次是基质体的剪切裂纹,ψ=150°时以层面、基质体的剪切裂纹为主。研究揭示了层状岩石逆倾向与顺倾向剪切的各向异性特征及差异性根源,可为各向异性力学模型完善、灾变机制及围岩稳定性分析提供科学依据。

     

    Abstract: The study of the bedding plane effect has important implications for stability analysis of deep rock masses. However, the differences in shear mechanical behavior between natural layered rocks under reverse and normal dip conditions are still not well understood. For this , a full-angle shear test of shale with 0°≤ψ≤180° (ψ is the bedding plane inclination angle, defined as the angle of clockwise rotation from the shear surface to the laminar surface) was carried out. The shear mechanical properties and differences in failure modes of shale under different bedding plane inclination angles were extensively analyzed. Additionally, the analysis results were supplemented and verified with discrete element simulations. The results are as follows. Firstly, the minimum shear strength is achieved when shearing parallel to the bedding plane. The strength reaches a maximum at ψ=30° and local peaks at 90° and 135°. The shear strength is relatively higher when shearing in the reverse direction. For ψ>30°, the shear strength generally decreases with ψ. Secondly, according to the differences in the shear mechanical behavior under various ψ, the layered rocks are divided into three groups: bedding tension and matrix shear group (ψ=15°-60°), matrix shear group (ψ=75°-120°), matrix and bedding shear group (135°-180°). Thirdly, In the pre-peak stage, stress drop phenomenon only exists in the matrix shear group. In the post-peak stage, stress drops in a “step-like” manner for bedding tension and matrix shear group. Fourthly, tension and shear failures coexist, with shear failure being predominant. Lastly, the number of shear cracks of layer is dominant when shearing parallel to the bedding plane. The number of shear cracks in the matrix is the highest at 90°. At ψ= 30°, the maximum number of tensile cracks is observed in the bedding plane, followed by shear cracks in the matrix. The shear cracks are mainly observed in the bedding and matrix at ψ= 150°. The study reveals the anisotropic characteristics and differences in reverse and normal dip shear of layered rocks. The results provide a scientific basis for improving anisotropic mechanical models and analyzing disaster mechanisms and surrounding rock stability.

     

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