This study aims at answering an important question: Is the joint roughness coefficient (JRC) a suitable parameter for quantifying the hydro-mechanical behavior of smooth to slightly rough rock joints? To answer this question, we used 3D printing technology to produce matched and mismatched joints with the same surface configuration (profile) and joints with identical JRC values but different surface configurations and measured the mechanical and hydraulic apertures (E and e). A novel and straightforward approach for generating joint profiles with controlled joint surface roughness (JRC = 3.5–5.8) was proposed, and the 3D-printed joint surfaces closely replicated target JRC values. The stress-dependent E and e of printed joint samples with designed surface configurations and JRC values were measured and fitted using semi-logarithmic closure model, revealing distinct trends for matched and mismatched joints. This study provides new insights into the applicability of the JRC in predicting stress-dependent apertures, particularly by distinguishing its predictive value (variability) in matched versus mismatched joint with identical and dissimilar surface configurations. By decoupling the effects of matedness, asperity geometry, and roughness magnitude, the study demonstrates that while JRC remains a reliable indicator for mismatched joints, it inadequately captures aperture variability in matched joints (within JRC range of 3–5), where surface geometry and matedness dominate. This work not only provides a reproducible method for joint fabrication but also offers critical insights into the limitations of JRC as a standalone descriptor, underscoring the need to incorporate surface configuration and joint matedness into future hydro-mechanical models.

中文翻译：

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光滑到略微粗糙的接头的配合、粗糙度和表面配置对应力相关孔径的影响

本研究旨在回答一个重要问题：节理粗糙度系数 （JRC） 是否是量化光滑至略微粗糙的岩石节理的水力学行为的合适参数？为了回答这个问题，我们使用 3D 打印技术生产具有相同表面配置（轮廓）的匹配和不匹配的接头，以及具有相同 JRC 值但表面配置的接头，并测量了机械和液压孔径（E 和 e）。提出了一种新颖而直接的方法，用于生成具有受控关节表面粗糙度 （JRC = 3.5–5.8） 的关节轮廓，并且 3D 打印的关节表面与目标 JRC 值非常相似。使用半对数闭合模型测量和拟合具有设计表面构型和 JRC 值的打印接头样品的应力依赖性 E 和 e，揭示了匹配和不匹配接头的不同趋势。这项研究为 JRC 在预测应力依赖性孔径方面的适用性提供了新的见解，特别是通过区分其在具有相同和不同表面配置的匹配和不匹配接头中的预测价值（可变性）。通过解耦嵌合度、凹凸几何形状和粗糙度大小的影响，该研究表明，虽然 JRC 仍然是不匹配接头的可靠指标，但它没有充分捕捉匹配接头中的孔径变化（在 JRC 3-5 范围内），其中表面几何形状和嵌合占主导地位。这项工作不仅为接头制造提供了一种可重复的方法，而且还为 JRC 作为独立描述符的局限性提供了重要见解，强调了将表面配置和接头配合纳入未来水力学模型的必要性。