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首页> 外文期刊>Pure and Applied Geophysics >Ultrasonic Velocities, Acoustic Emission Characteristics and Crack Damage of Basalt and Granite
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Ultrasonic Velocities, Acoustic Emission Characteristics and Crack Damage of Basalt and Granite

机译：玄武岩和花岗岩的超声速度，声发射特征和裂纹损伤

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摘要

Acoustic emissions (AE), compressional (P), shear (S) wave velocities, and volumetric strain of Etna basalt and Aue granite were measured simultaneously during triaxial compression tests. Deformation-induced AE activity and velocity changes were monitored using twelve P-wave sensors and eight orthogonally polarized S-wave piezoelectric sensors; volumetric strain was measured using two pairs of orthogonal strain gages glued directly to the rock surface. P-wave velocity in basalt is about 3 km/s at atmospheric pressure, but increases by > 50% when the hydrostatic pressure is increased to 120 MPa. In granite samples initial P-wave velocity is 5 km/s and increases with pressure by < 20%. The pressure-induced changes of elastic wave speed indicate dominantly compliant low-aspect ratio pores in both materials, in addition Etna basalt also contains high-aspect ratio voids. In triaxial loading, stress-induced anisotropy of P-wave velocities was significantly higher for basalt than for granite, with vertical velocity components being faster than horizontal velocities. However, with increasing axial load, horizontal velocities show a small increase for basalt but a significant decrease for granite. Using first motion polarity we determined AE source types generated during triaxial loading of the samples. With increasing differential stress AE activity in granite and basalt increased with a significant contribution of tensile events. Close to failure the relative contribution of tensile events and horizontal wave velocities decreased significantly. A concomitant increase of double-couple events indicating shear, suggests shear cracks linking previously formed tensile cracks.
机译：在三轴压缩试验中，同时测量了埃特纳玄武岩和Aue花岗岩的声发射（AE），压缩（P），剪切（S）波速以及体积应变。使用十二个P波传感器和八个正交极化的S波压电传感器监测变形引起的AE活动和速度变化。使用直接粘贴在岩石表面的两对正交应变计测量体积应变。在大气压下，玄武岩中的P波速度约为3 km / s，但当静水压力增加至120 MPa时，P波速度增加> 50％。在花岗岩样品中，初始P波速度为5 km / s，并随压力增加<20％。压力引起的弹性波速度变化表明两种材料中的长径比均符合标准，并且埃特纳玄武岩还包含高径比孔隙。在三轴载荷下，玄武岩的应力引起的P波速度各向异性明显高于花岗岩，垂直速度分量比水平速度快。然而，随着轴向载荷的增加，玄武岩的水平速度显示出很小的增加，而花岗岩的水平速度显示出明显的下降。使用第一运动极性，我们确定了样品在三轴加载过程中产生的AE源类型。随着微分应力的增加，花岗岩和玄武岩中的AE活性也随之增加，而拉伸事件的贡献也很大。接近破坏时，拉伸事件和水平波速度的相对贡献显着下降。伴随着剪切作用的双偶事件的同时增加，表明剪切裂纹与先前形成的拉伸裂纹有关。

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