Abstract We present coupled Thermo–Hydro–Mechanical (THM) modeling of geologic nuclear waste disposal in argillaceous claystone, focusing on thermally-induced pressure changes and the potential for such pressure changes to induce hydro-fracturing. To investigate this possibility, we first conduct a three-dimensional repository scale model, with host rock properties, repository design, and nuclear waste decay heat functions derived from the French concept of geologic disposal in argillaceous claystone. The model simulations show that the highest potential for hydro-fracturing occurs between emplacement micro-tunnels (cells) at the center rather than at the edge of the repository. We further investigate the use of a two-dimensional single cell model as a simpler surrogate for a full three-dimensional model. Our results reveal that such geometric simplification is reasonably accurate for modeling coupled THM processes at the center of the repository, though it overestimates the likelihood for hydro-fracturing and substantially overpredicts ground surface uplift. A parameter study shows the importance of adjacent higher permeability geological layers that play a significant role in dissipating overpressure in the host rock layer. Finally, the study shows the importance of the spacing between emplacement tunnels, which if too short results in a higher fluid pressure and a strongly increased potential for hydro-fracturing. Overall, the study suggests, the limiting factor in the thermal management and design of a repository is not necessarily the maximum temperature in the engineered barrier system near the waste packages, but rather the more modest host rock temperature between emplacement tunnels, due to the potential for thermal damage.

中文翻译：

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泥质粘土岩中与核废料处理相关的热加压和水力压裂潜力的研究

摘要 我们提出了泥质粘土岩中地质核废料处理的热-水-机械耦合 (THM) 建模，重点是热引起的压力变化和这种压力变化引起水力压裂的可能性。为了研究这种可能性，我们首先进行了一个三维储存库比例模型，其中包含源自法国泥质粘土岩地质处置概念的主岩性质、储存库设计和核废料衰变热函数。模型模拟表明，水力压裂的最高潜力发生在中心的就位微隧道（单元）之间，而不是在储存库的边缘。我们进一步研究了使用二维单细胞模型作为完整三维模型的简单替代品。我们的结果表明，这种几何简化对于在储存库中心模拟耦合 THM 过程是相当准确的，尽管它高估了水力压裂的可能性并大大高估了地表隆起。一项参数研究表明相邻的高渗透性地质层的重要性，这些地质层在消散主岩层中的超压方面起着重要作用。最后，该研究表明了就位隧道之间的间距的重要性，如果太短会导致更高的流体压力和水力压裂的潜力大大增加。总体而言，研究表明，处置库热管理和设计的限制因素不一定是废物包附近工程屏障系统的最高温度，