Fracture Characteristics of Layered Phyllite
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摘要: 采用中心直切槽半圆盘层状岩样测试了层状千枚岩的断裂性能,并基于黏结单元建立了层状岩石的有限元数值计算模型,系统研究了层理倾角、层理强度、层理间距及切缝倾角等参数对层状千枚岩断裂特性的影响。结果表明:当层理倾角在0°~90°范围内时,Ⅰ型断裂韧度逐渐增大,峰值载荷和峰值位移也呈增大趋势;层理倾角为零时,发生张拉破坏。层理倾角在15°~45°时,剪切破坏占主导;层理倾角在60°~90°时,张拉破坏占主导。层理倾角为零时,破坏模式受层理强度影响较小;层理倾角分别为15°和30°时,随着层理强度增大,试样由剪切破坏向拉-剪耦合破坏演化;层理倾角在45°~90°时,试样均呈现拉-剪耦合破坏,且随着层理强度增大,试样有向拉伸破坏为主演化的趋势。层理间距较小时,裂纹呈沿层–穿层阶梯状扩展趋势明显;切缝倾角较大时,裂纹穿层扩展趋势明显。Abstract: Based on the half-disk layered rock sample with central straight cutting groove, tests on fracture performances of layered phyllite were conducted, and the finite element numerical model of layered rock was developed. The influences of bedding dip angle, bedding strength, bedding thickness, span and different cutting angle on the fracture performances of layered phyllite was systematically studied. The results show that with the change of bedding dip angle from 0° to 90°, model Ⅰ fracture toughness value increases gradually, and the peak load and peak displacement also show increasing trend. When the bedding dip angle is 0°, the tensile failure occurs. When the bedding dip angle is 15°−45°, the shear failure is dominant, and when the bedding dip angle is 60°−90°, the tensile failure is dominant. When the bedding dip angle is 0°, the failure mode is less affected by the bedding strength. For cases with angle of 15° and 30°, with the increase of bedding strength, the specimen changes from shear failure to tensile-shear coupling failure. As the angle ranges from 45° to 90°, the specimens show tensile-shear coupling failure. With the increase of bedding strength, the specimens seem to fail by tension. When the bedding distance is small, the crack shows an obvious ladder-like growth along the bedding plane.
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表 1 中心直切槽半圆盘无量纲应力强度因子结果比较[27]
Table 1. Comparison of dimensionless stress intensity factor for a half disk with a central straight slotted[27]
a/R S/R YⅠ Error/% This paper Ref.[27] 0.1 0.5 2.752 2.724 1.03 0.3 0.5 2.493 2.538 −1.77 0.8 0.5 12.850 12.665 1.46 表 2 模型中的单元力学细观参数
Table 2. Microscopic parameters of element mechanics in the model
Element type Location Elastic modulus/GPa Poisson’s ratio Density/(kg·mm−3) Entity element Rock material 37.76 0.23 2.623 × 103 Element type Location Tensile strength/MPa Shear strength/MPa Normal stiffness/(MPa·mm−1) Tangential stiffness/(MPa·mm−1) Failure displacement/mm Cohensive element Bedding 3.3 9 9442 3838 0.05 Stroma 6.6 19 37768 15353 0.10 表 3 不同层理倾角试样的试验与数值模拟结果对比
Table 3. Comparison between experimental and numerical simulationresults of specimens with different bedding dip angles
Bedding dip angle/(°) Load-displacement curves Test failure result Simulated failure result 0 15 30 45 60 75 90 表 4 各层理倾角试样在不同层理强度下的数值模拟破坏结果
Table 4. Numerical failures of each bedding dip angles' specimen under different bedding strength
Bedding dip angle/(°) Simulated result 0.5 0.8 1.1 1.5 0 15 30 45 60 75 90 表 5 各层理倾角试样在不同层理间距下的数值模拟破坏结果
Table 5. Numerical simulation failure results of each bedding dip angles' specimen under different bedding distance
Bedding dip angle/(°) Simulated result d=3 mm d=5 mm d=8 mm d=12 mm 0 15 30 45 60 75 90 表 6 各层理倾角试样在不同切缝倾角下的数值模拟破坏结果
Table 6. Numerical failures of each bedding dip angles' specimen under different cutting seam dip angles
Bedding dip angle/(°) Simulated result β=0° β=30° β=45° β=60° 0 15 30 45 60 75 90 -
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