Study on Time-Dependent Closure Behavior of Rock Fractures Subject to Normal Stress
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摘要: 基于不同高径比微凸体的受压时效性试验,根据赫兹接触理论,得到了不同微凸体弹性模量随时间的衰减规律. 对红砂岩和石灰岩新鲜裂隙面开展了不同法向应力条件下的受压时变闭合试验,结合小波分析法、区域生长算法和参考面法,提出了一种岩石裂隙细观尺度微凸体形貌的识别方法,对比了试验前后微凸体数量、高度和高径比的差异. 建立了考虑微凸体间相互作用的接触力学模型,求解Boussinesq方程并考虑弹性模量随时间的衰减,对两种岩石裂隙开展了逐级增加应力条件下的受压时变闭合计算. 通过对比计算和试验得到的损伤面积和蠕变变形验证了模型的有效性,阐明了微凸体的应变、接触面积和接触应力随时间的演化规律,揭示了不同细观形貌特征的微凸体在裂隙受压时变闭合过程中的关键性作用.Abstract: This study conducted time-dependent compression tests on asperities with different height-to-radius ratios using ultra-hard gypsum. According to Hertz contact theory, the attenuation laws of the elastic modulus of different asperities over time were fitted. Time-dependent closure tests were performed on fresh fracture surfaces of red sandstone and limestone under varying normal stresses. By integrating wavelet analysis, region growth algorithms, and the reference surface method, a novel approach was developed for identifying the mesoscale asperity morphology of rock fractures, and compared the differences in the number, height, and height-to-radius ratio of asperities before and after the experiment. Utilizing Boussinesq's solution, an influence matrix was constructed to account for interactions between asperities. Based on the law of the elastic modulus decaying over time, enabling time-dependent closure calculations for different rock fractures under variable stress conditions. This approach precisely analyzes the temporal evolution of strain, contact area, and contact stress for individual asperity, with simulation results matching experimental data in terms of damage area and creep deformation. The study reveals the pivotal role of asperities with distinct mesoscale morphological features in the time-dependent closure process of rock fractures under compression.
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Key words:
- rock fracture /
- asperity /
- morphological characteristics /
- time-dependent closure /
- Hertzian contact /
- rock mechanics
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图 6 不同岩石裂隙表面微凸体识别结果(单位:mm)
a.裂隙面微凸体识别效果(以红砂岩为例);b.微凸体概化为半椭球体;c.分水岭方法的局限性(Wen et al.,2022);d.红砂岩和石灰岩裂隙面微凸体分布图
Fig. 6. Identification results of asperities on rock fracture surfaces (unit: mm)
表 1 弹性模量衰减拟合参数
Table 1. Parameters of different types of rock samples

A(103 GPa) B(103 GPa) R2 A-1 1.718 3.152 0.933 A-2 8.509 6.463 0.997 A-3 22.916 13.250 0.995 表 2 不同类型岩石试样参数
Table 2. Parameters of different types of rock samples
名称 密度(g/cm3) 单轴抗压强度(MPa) 泊松比 弹性模量(GPa) 抗拉强度(MPa) 硬度(MPa) 相对硬度 红砂岩 2.5 45.8 0.30 26.8 3.1 29.5 0.02 石灰岩 2.7 190.0 0.25 35.5 12 74.7 0.04 -
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