Managing fluid-driven fracture networks is crucial for subsurface resource utilization, yet the current understanding of the key controlling factors remains insufficient. While geologic discontinuities have been shown to significantly influence fracture network complexity, this study identifies another major contributor. We conducted a new set of experiments using a transparent true triaxial cell, which enabled video recording of the temporal evolution of fluid-driven fracture paths. Using pseudo-2D samples without macroscale structural discontinuities, we observed multiple occurrences of hydraulic fracture curving and branching under anisotropic boundary stresses. We proposed a theoretical model demonstrating that the stress parallel to the crack line in the solid matrix near the crack tip (i.e., the T-stress) accounts for the observed fracture curving behavior. This finding suggests that T-stress is an additional mechanism contributing to the complexity of fluid-driven fracture networks in the subsurface, besides the geologic discontinuities.

中文翻译：

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由裂纹平行应力引起的复杂流体驱动裂缝


管理流体驱动的裂缝网络对于地下资源利用至关重要，但目前对关键控制因素的理解仍然不足。虽然地质不连续性已被证明会显着影响裂缝网络的复杂性，但本研究确定了另一个主要因素。我们使用透明的真三轴单元进行了一组新的实验，该实验能够对流体驱动的断裂路径的时间演变进行视频记录。使用没有宏观结构不连续性的伪 2D 样品，我们观察到在各向异性边界应力下多次出现水力裂缝弯曲和分支。我们提出了一个理论模型，证明平行于裂纹尖端附近固体基体中裂纹线的应力（即 T 应力）解释了观察到的断裂弯曲行为。这一发现表明，除了地质不连续性之外，T 应力是导致地体驱动裂缝网络复杂性的另一种机制。