ANISOTROPIC BEHAVIOR AND MECHANISM OF DRY AND WATER-BEARING SCHIST IN TERMS OF CHARACTERISTIC STRENGTH AND ENERGY EVOLUTION
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摘要: 以石英云母片岩为对象,采用单轴压缩试验,探讨这类脆性片理化岩石在干燥和含水状态下的特征强度与能量演化的加载方向效应,并结合微观组构特征与宏观破坏模式,揭示片岩力学行为各向异性的机制。结果表明:(1)加载过程中,能量演化曲线与岩石的变形损伤变化有较好的对应关系,据此可快速准确地确定岩石的特征强度;(2)干燥和含水状态下片岩的特征强度皆表现为α=90°>α=0°>α=30°,其中,α=30°时,片岩强度对水的响应更为敏感,水对片岩的强度各向异性有一定增强作用;(3)α=90°试样的能量存储与耗散始终高于α=0°、30°试样,但相比α=90°而言,α=30°时,片岩的岩爆倾向性更强,岩石的损伤发展较为迅速;(4)岩石中的片状矿物和微裂隙为水的润滑、软化、水楔作用提供了物质基础,占主导地位的水作用随加载方向有所不同;(5)岩石内的片状矿物定向排列与软硬层近互层状分布的微观结构决定了裂纹产生与扩展机制的加载方向效应,本质上控制着岩石的强度与能量的各向异性。Abstract: In this study,the quartz mica schist was taken as the tested object. The uniaxial compression test was used to explore the influence of loading direction on the characteristic strength and energy evolution of this brittle schistose rock under dry and water-bearing conditions. Combined with the characteristics of micro fabric and macro failure mode,the mechanism of mechanical anisotropic behavior of schist was revealed. Results show the following. (1)During the loading process,the energy evolution curves of rocks have a good corresponding relationship with the deformation damage changes. Based on this,the characteristic strengths of rocks can be determined quickly and accurately. (2)The characteristic strengths of schist in both dry and water-bearing states always follow α=90°>α=0°>α=30°. At α=30°,the schist has a more sensitive response to water with respect to the characteristic strength. Water enhances the strength anisotropy of schist to a certain extent. (3)At α=90°,the energy storage and dissipation of schist are always higher than those at α=0° and 30°.The tendency of rock burst of schist with α=30° is stronger than that with α=90°.The damage of rock has a relatively rapid development at α=30°. (4)The flaky minerals and micro-cracks in schist provide the material basis for water effects such as lubrication,softening and water wedge.The dominant water action varies with the loading direction. (5)The quartz mica schist has the microscopic characteristics of orientation arrangement of flake minerals and the interlayered distribution of soft and hard layers. This typical structure determines the effect of loading direction on the mechanism of cracks generation and propagation,and essentially controls the anisotropy of strength and energy of the rock.
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Key words:
- Schist /
- Characteristic strength /
- Energy evolution /
- Anisotropy /
- Mechanism
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图 17 片状云母对裂纹扩展的阻碍作用
(根据Rawling et al.(2002)绘制)
Figure 17. Inhibitory effect of flaky mica on crack propagation
(plotted according to Rawling et al.(2002))
表 1 片岩样品的特征强度值
Table 1. Characteristic strength value of schist specimens
样品标号 特征强度值(能量曲线法) 特征强度值(应变测量法) σcc σci σcd σf σcc σci σcd σf D0 46.41 73.64 92.20 97.96 47.83 68.05 52.26* 97.96 D30 33.03 45.29 55.50 57.80 31.13 44.23 53.78 57.80 D90 61.84 92.54 110.88 121.37 61.43 90.32 111.38 121.37 S0 27.24 36.38 39.85 40.68 26.06 37.12 29.43* 40.68 S30 12.63 17.58 18.97 19.57 12.16 16.52 16.65 19.57 S90 24.53 41.15 53.31 62.31 25.64 41.89 56.07 62.31 样品标号中的首字母代表样品状态(D表示干燥状态,S表示含水状态),数字代表片理角度,下同。带“*”的表示异常值 表 2 干燥试样在临界应力点处的能量值
Table 2. Energy values of dry specimens corresponding to the critical stress points
临界应力σ 样品标号和能量值/kJ·m-3 D0 D30 D90 U Ue Ud U Ue Ud U Ue Ud σcc 26.49 21.40 5.09 21.07 16.96 4.11 87.40 61.36 26.04 σci 53.43 48.25 5.18 36.93 32.81 4.12 161.09 135.05 26.04 σcd 87.24 81.28 5.96 53.64 49.16 4.48 227.40 200.17 27.23 σf 128.32 91.44 36.88 61.79 54.68 7.11 302.13 237.70 64.43 表 3 含水试样在临界应力点处的能量值
Table 3. Energy values of water-bearing specimens corresponding to the critical stress points
临界应力σ 样品标号和能量值/kJ·m-3 S0 S30 S90 U Ue Ud U Ue Ud U Ue Ud σcc 19.46 14.73 4.73 15.04 11.73 3.31 19.63 13.45 6.18 σci 31.12 26.28 4.84 25.59 22.24 3.35 44.08 37.72 6.36 σcd 36.37 31.50 4.87 29.38 25.95 3.43 72.99 63.46 9.53 σf 38.23 32.78 5.45 31.91 27.75 4.16 120.52 86.59 33.93 -
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