The implementation of distributed strain measurement methods in triaxial and uniaxial tests have demonstrated the development of strain localization, even at early stages. This implies that single point measurement methods are location dependent. The use of distributed methods is required not only to improve the interpreted constitutive parameters obtained from triaxial tests, but also to understand the implications of strain localization in the failure process. This work uses optical fibers in triaxial tests. The developed distributed measurement method was implemented on granite, gabbro, and sandstone samples and tested under different confining pressures, reaching 200 MPa on the granite sample. Using a temporal resolution of 0.25 Hz and 5 mm of spatial resolution, the strain evolution at over 300 locations at the sample surface was measured during testing. When compared to point sensing methods, the use of optical fiber greatly increases the number of measurements at the surface of the sample, and their interpolation provides the entire deformation of the sample surface. In all the tests performed, strain localizations were revealed before failure. A three-dimensional interpretation of a test, combining an optical scan of the sample and the distributed measurements, show good correlation between the fractures and the strain localization.

中文翻译：

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三轴试验中岩石变形和破坏的分布式光纤测量

在三轴和单轴测试中分布式应变测量方法的实施已经证明了应变局部化的发展，即使在早期阶段也是如此。这意味着单点测量方法取决于位置。分布式方法的使用不仅需要改进从三轴试验中获得的解释本构参数，而且还需要了解应变局部化在失效过程中的含义。这项工作在三轴测试中使用光纤。所开发的分布式测量方法在花岗岩、辉长岩和砂岩样品上实施，并在不同的围压下进行了测试，在花岗岩样品上达到了 200 MPa。使用 0.25 Hz 的时间分辨率和 5 mm 的空间分辨率，在测试期间测量了样品表面 300 多个位置的应变演变。与点传感方法相比，光纤的使用大大增加了样品表面的测量次数，并且它们的插值提供了样品表面的整个变形。在所有进行的测试中，应变定位在失败之前就已经显现出来。结合样品的光学扫描和分布式测量的测试的三维解释显示裂缝和应变定位之间的良好相关性。在失败之前揭示了应变定位。结合样品的光学扫描和分布式测量的测试的三维解释显示裂缝和应变定位之间的良好相关性。在失败之前揭示了应变定位。结合样品的光学扫描和分布式测量的测试的三维解释显示裂缝和应变定位之间的良好相关性。