Construction of cavities in the subsurface is always accompanied by excavation damage. Especially in the context of deep geological nuclear waste disposal, the evolving excavation damaged zone (EDZ) in the near field of emplacement tunnels is of utmost importance concerning safety aspects. As the EDZ differs from the intact host rock due to enhanced hydraulic transmissivity and altered geomechanical behavior, reasonable and location-dependent input data on hydraulic and mechanical properties are crucial. Thus, in this study, a hydromechanical characterization of an EDZ in the Mont Terri underground rock laboratory, Switzerland, was performed using three different handheld devices: (1) air permeameter, (2) microscopic camera and (3) needle penetrometer. The discrete fracture network (DFN), consisting of artificially induced unloading joints and reactivated natural discontinuities, was investigated by a portable air permeameter and combined microscopic imaging with automatic evaluation. Geomechanical and geophysical characterization of the claystone was conducted based on needle penetrometer testing at the exposed rock surface. Within the EDZ, permeable fractures with a mean hydraulic aperture of 84 ± 23 µm are present. Under open conditions, self-sealing of fractures is suppressed, and cyclic long-term fracture aperture oscillations in combination with closure resulting from convergence processes is observed. Based on measured needle penetration indices, a uniaxial compressive strength of 30 ± 13 MPa (normal to bedding) and 18 ± 8 MPa (parallel to bedding) was determined. Enhanced strength and stiffness are directly related to near-surface desaturation of the claystone and a sharp decrease in water content from 6.6 wt % to 3.7 wt %. The presented methodological approach is particularly suitable for time-dependent monitoring of EDZs since measurements are nondestructive and do not change the actual state of the rock mass. This allows for a spatially resolved investigation of hydraulic and mechanical fracture apertures, fracture surface roughness, and physico-mechanical rock parameters and their intra-facies variability.

中文翻译：

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瑞士 Mont Terri 岩石实验室 Opalinus 粘土中开挖损坏区 (EDZ) 的机械和水力特性

在地下建造空洞总是伴随着开挖损坏。特别是在深部地质核废料处置的背景下，安放隧道近场不断演变的开挖破坏区（EDZ）对于安全问题至关重要。由于 EDZ 由于增强的水力透射率和改变的地质力学行为而不同于完整的主岩，因此关于水力和力学特性的合理且与位置相关的输入数据至关重要。因此，在本研究中，瑞士 Mont Terri 地下岩石实验室的 EDZ 的流体力学特性是使用三种不同的手持设备进行的：(1) 空气渗透计，(2) 显微相机和 (3) 针式渗透计。离散断裂网络（DFN），由人工诱导的卸载接头和重新激活的自然不连续性组成，通过便携式空气渗透计和显微成像与自动评估相结合进行了研究。粘土岩的地质力学和地球物理特征是基于裸露岩石表面的针入度计测试进行的。在 EDZ 内，平均水力孔径为 84 的可渗透裂缝 ±  23  µm存在。在开放条件下，裂缝的自封闭受到抑制，并且观察到周期性的长期裂缝孔径振荡与收敛过程导致的闭合相结合。根据测得的针刺指数，单轴抗压强度为 30  ±  13 MPa（垂直于床上用品）和 18  ± 8 MPa（平行于垫层）被确定。增强的强度和刚度与粘土岩的近表面去饱和和含水量从 6.6 wt% 急剧下降到 3.7 wt% 直接相关。所提出的方法特别适用于 EDZ 的时间相关监测，因为测量是非破坏性的，不会改变岩体的实际状态。这允许对水力和机械裂缝孔径、裂缝表面粗糙度和物理力学岩石参数及其相内变化进行空间解析研究。