ISSN 1000-3665 CN 11-2202/P

    基于声发射的张开型单裂隙岩石裂纹扩展行为特性研究

    Investigation of crack propagation behavior of opening single fractured rock based on acoustic emission technology

    • 摘要: 裂隙形态对岩石力学性能和裂纹扩展行为有重要影响,为此分别针对完整花岗岩试样和不同预制裂隙倾角(0°、15°、30°、45°、60°、75°、90°)的花岗岩试样开展了单轴压缩试验,并同步进行了声发射监测和高清摄像记录。试验测试结果表明,随着裂隙倾角的增大,岩石的裂纹起裂角度逐渐减小,岩石的峰值强度、起裂应力和峰值应变均呈逐渐增大趋势,而弹性模量呈现出先增大后减小的变化规律;岩石应力-应变关系曲线的初始压密段和线弹性段对应声发射平静期,荷载超过起裂应力后声发射进入发展期,荷载接近峰值强度时声发射处于高峰期直到岩石完全破坏;裂隙倾角越大,声发射高峰期的持续时间越长,累计振铃计数越多,岩石峰值强度与累计振铃计数之间有良好的线性关系,并量化了裂隙形态对岩石强度损伤影响规律;随着裂隙倾角的增大,岩石的破裂模式由剪切断裂逐渐向张拉断裂过渡。根据岩石轴向应力与累计声发射撞击数之间的关系曲线,并结合岩石起裂应力的计算方法,计算值略大于摄像观测值,二者之间的误差范围介于1.7%~6.9%,表明起裂应力的计算方法是合理的。上述成果对深入研究裂隙岩体的工程性质和破坏模式具有重要参考意义。

       

      Abstract: The fissure morphology has an important influence on rock mechanical properties and crack propagation behavior. A series of uniaxial compression tests were carried out on the intact granite samples and granite samples with different prefabricated fissure dip angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°). Simultaneously, the rock failure process was monitored and recorded by acoustic emission (AE) and high-definition camera, respectively. As the fissure dip angle increases, the test results indicate that the crack initiation angle of rock decreases gradually; the peck strength, crack initiation stress, and peak strain of all the fractured rocks are increased gradually. The elastic modulus of rock increases firstly and then decreases with the increase of fracture dip angle. The initial compaction section and linear elastic section of the rock stress-strain relationship curve correspond to the quiet period of acoustic emission. The acoustic emission enters the development period after the load exceeds the crack initiation stress. When the load approaches the peak strength, the acoustic emission is in the peak period until the rock failure completely. The lager the fracture dip angle, the longer the peak duration period of acoustic emission and the more in quantity of the cumulative ringing count. A good linear relationship is presented between fracture rock peak strength and cumulative ringing count, and the influence of crack shape on rock strength damage is quantified. With the increase of fissure dip angle, the fracture mode of rock gradually transitions from shear fracture to tensile fracture. According to the relationship curves between rock axial stress and cumulative AE impact number, combined with the calculation method of rock initiation stress, It found that the calculated value is slightly larger than the camera observation value with the error range of 1.7% ~ 6.9%, indicating that the calculation method of rock crack initiation stress is reasonable. This study provides basic information for investigating the engineering properties and failure mode of fracture rock.

       

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