Experimental Study on Acoustic Emission and Crack Propagation of Fissured Sandstone with Different Moisture States
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摘要: 为进一步揭示不同含水状态陡倾裂隙砂岩的裂纹扩展规律及破坏特征,开展了干燥、自然与饱水3种含水状态下陡倾裂隙砂岩的单轴压缩试验,采用声发射技术和数字图像相关技术,分析了不同含水状态对裂隙砂岩力学特性、声发射特性及裂纹演化特征的影响。结果表明:水的存在对裂隙砂岩的抗压强度、弹性模量及峰值应变具有明显劣化作用,随着含水率增加,各力学参数呈现出近线性递减的变化趋势;不同含水状态下裂隙砂岩的宏观破坏模式均表现为H形张拉-剪切混合破坏,且张拉裂纹随含水率的增加而增多,次生裂纹也主要以张拉裂纹的形式扩展;裂隙砂岩的声发射能量计数随含水率的增加逐渐削弱,累计能量曲线呈现出明显的阶段性特征,且不同含水状态下其分布特征差异明显,结合声发射与数字图像相关技术两种分析方法,有助于从宏细观角度揭示裂隙砂岩的裂纹演化规律,依据应变局部化带可有效预测裂纹萌生与扩展方向,含水率的增加加快了裂纹萌生速率,减缓了加载后期裂纹扩展速率;基于声发射参数的微裂纹分析结果与宏观破坏模式基本一致,不同含水状态对裂隙砂岩拉剪裂纹的影响差异明显,含水率的增加促进了裂隙砂岩内部张拉裂纹的发育,进而抑制了剪切裂纹的发育。研究结果可为受水影响下裂隙岩石的稳定性评估及监测研究提供相关参考。Abstract: To further reveal the crack propagation law and failure characteristics of fissured sandstone with different moisture states, the uniaxial compression tests of steeply dipping fissured sandstone were carried out with different moisture states of dry, natural, and saturated. Acoustic emission (AE) and digital image correlation (DIC) techniques were used to analyze the effects of moisture state on the mechanical properties, AE characteristics, and crack evolution characteristics of fissured sandstone. The results show that water has a significant deterioration effect on the compressive strength, elastic modulus and peak strain of the fissured sandstone, and the mechanical parameters show a nearly linear decreasing trend as moisture content increases. The macroscopic failure mode of the fissured sandstone all exhibits H-type tensile-shear mixed failure under different moisture states, and the tensile cracks gradually increase with increasing moisture content, the secondary cracks also propagate mainly in the form of tensile cracks. As moisture content increases, the AE energy counts of fissured sandstone weaken gradually, the cumulative energy curve presents obvious stage characteristics and its distribution characteristics vary significantly with the moisture state. The combination of AE and DIC analysis methods is helpful to reveal the crack evolution law of fissured sandstone from the macro-meso perspective. The crack initiation and propagation orientation can be effectively predicted according to the strain localization zone, and the increase in moisture content speeds up the crack initiation rate and slows down the crack propagation rate in the later stage of loading. The results of micro-crack analysis based on the AE parameters are basically consistent with the macroscopic failure mode. The effect of moisture state on tensile and shear cracks in fissured sandstone varies significantly, with increasing moisture content promoting the development of tensile cracks and thereby inhibiting the development of shear cracks. The research results can provide a reference for the stability evaluation and monitoring of fissured rock under the effect of water.
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表 1 试样信息
Table 1. Information of the specimens
Sample State Diameter/mm Height/mm Mass/g w/% D-60 Dry 49.83 99.94 459.26 0 N-60 Natural 49.79 99.46 466.14 1.476 S-60 Saturated 49.71 100.03 481.22 4.563 -
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