Discrete element simulation of shale softening based on parallel-bonded water-weakening model
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摘要: 基于颗粒离散元方法,通过构建损伤因子,提出了平行黏结水弱化模型,建立了考虑胶结物力学参数的非均质性的颗粒流模型。通过室内试验和数值模拟计算结果的对比分析,验证了所提模型的正确性和适用性。主要结论如下：①岩石胶结物的非均质性对岩石宏观力学性质存在一定影响。随着均质性因子m的增加,岩石均质性增加,单轴抗压强度和弹性模量也随之增加,符合指数函数关系；②随着黏结面积系数的增加,岩石所储存的总应变能的总量和增速逐渐降低；③岩石在干燥状态下,微裂纹倾角集中于80°～100°,随着黏结面积系数的增加,微裂纹倾角的分布范围逐渐增加；④随着黏结面积系数的增加,岩石破裂面更为密集,且贯通性增强。研究结果可为深埋隧道遇水产生围岩大变形、库岸涉水边坡变形等问题的细观机制研究提供了一定的依据和理论指导。Abstract: Based on the discrete element method of particles, by constructing damage factors, a parallel-bonded water-weakening model is proposed, and a particle flow code model considering the heterogeneity of the mechanical parameters of the cement is established. The comparison and analysis of the results of indoor experiments and numerical simulations verify the correctness and applicability of the proposed model. The main conclusions are as follows: (1) The heterogeneity of rock cement has certain influences on the macroscopic mechanical properties of rock. As the homogeneity factor increases, the homogeneity of the rock increases, and the uniaxial compressive strength and elastic modulus also increase, which conforms to the exponential function relationship. (2) With the increase of the bond area coefficient, the total amount and growth rate of the stored total strain energy in the rock gradually decrease. (3) In the dry state of the rock, the inclination angle of micro-cracks is concentrated in 80°~100°. As the bond area coefficient increases, the distribution range of the inclination angle of micro-cracks gradually increases. (4) With the increase of the bond area coefficient, the rock fracture surface is denser and the penetration is enhanced. The research results can provide a certain basis and theoretical guidance for the meso-mechanism study on the large deformation of the surrounding rock caused by the water in deep-buried tunnels and the deformation of the wading slope of the reservoir bank.
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图 1 宏观损伤因子与浸水时间的关系
Figure 1. Relationship between macro-damage factor and water immersion time
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图 3 细观损伤因子随浸水时间的关系
Figure 3. Relationship between mesoscopic damage factor and immersion time
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图 4 数值模拟与室内试验结果对比
Figure 4. Comparison between numerical simulation and laboratory test results
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图 5 平行黏结半径乘子概率密度（Sr=0.888,
=0.486） Figure 5. Probability density of parallel bond radius multipliers
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图 6 宏观力学性质与均质性因子的关系
Figure 6. Relationship between macro-mechanical properties and homogeneity factors
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图 7 均质性因子m和黏结面积系数Sr耦合对岩石宏观力学性质的影响
Figure 7. Effects of homogeneity factor and bonded area coefficient coupling on macro-mechanical properties of rock
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图 8 模型能量耗散与应力–应变关系(Sr=0.432)
Figure 8. Energy dissipation and stress-strain relationship of model
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图 9 总应变能与黏结面积系数的关系
Figure 9. Relationship between total strain energy and bonded area coefficient
表 1 PWW模型计算参数
Table 1 Parameters of PWW model
时间/d 弹性模量/GPa 宏观损伤因子 细观损伤因子 平行黏结半径乘子特征值 黏结面积/m2 黏结面积系数 0 27.38 0.000 0.000 1.000 30.14 0.000 2 25.67 0.062 0.051 0.949 28.62 0.087 15 20.90 0.236 0.251 0.749 22.61 0.432 30 17.59 0.357 0.412 0.588 17.73 0.712 50 13.55 0.505 0.514 0.486 14.65 0.888 70 12.36 0.548 0.550 0.450 13.57 0.950 90 11.40 0.583 0.579 0.421 12.70 1.000 
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表 2 颗粒流模型细观参数
Table 2 Mesoscopic parameters of particle flow code model
参数 取值 颗粒密度/(kg·m-3) 2650.0 最小粒径/mm 0.15 粒径比 1.66 颗粒接触模量/GPa 13.5 颗粒刚度比 3.0 颗粒摩擦系数 0.5 均质性因子 10.0 平行黏结模量/GPa 13.5 平行黏结刚度比 3.0 平行黏结抗拉强度/MPa 20.55 平行黏结黏聚力/MPa 40.55 平行黏结内摩擦角/(°) 30.0
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