Abstract. 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 is crucial. Thus in this study, a hydro-mechanical 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 penetration test. The discrete fracture network (DFN), consisting of artificially induced unloading joints and reactivated natural discontinuities, was investigated by a portable air permeameter as well as 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 is 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 as well as physico-mechanical rock parameters and their intra-facies variability.

中文翻译：

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瑞士Mont Terri岩石实验室的Opalinus粘土中的挖掘破坏区（EDZ）的机械和水力特性

摘要。地下空腔的建造总是伴随着挖掘破坏。特别是在深部地质核废料处置的背景下，就安全方面而言，就座隧道的近场中不断演变的挖掘破坏区（EDZ）至关重要。由于EDZ与完整的基岩不同，这归因于水力传输率的提高和地质力学行为的改变，因此有关水力和机械特性的合理且位置相关的输入数据至关重要。因此，在这项研究中，使用三种不同的手持式设备在瑞士Mont Terri地下岩石实验室中对EDZ进行了水力力学表征：（1）透气度仪，（2）显微相机和（3）针刺测试。离散断裂网络（DFN），通过便携式空气渗透仪以及结合了自动评估的显微成像技术，研究了由人工引起的卸荷缝和重新激活的自然间断组成的结构。粘土的地球力学和地球物理特征是在裸露的岩石表面通过针入针度计测试进行的。在EDZ中，存在平均水力孔径为84±23 µm的渗透性裂缝。在开放条件下，裂缝的自密封性受到抑制，观察到周期性长期裂缝孔径振荡以及由于收敛过程而导致的闭合。根据测得的针刺指数，确定单轴抗压强度为30±13 MPa（垂直于床上用品）和18±8 MPa（平行于床上用品）。强度和刚度的提高直接与粘土岩的近表面去饱和和含水量从6.6 wt .-％急剧降低到3.7 wt .-％直接相关。所提出的方法学方法特别适合于EDZ的时变监测，因为测量结果无损且不会改变岩体的实际状态。这样就可以对水力压裂和机械压裂孔径，压裂表面粗糙度以及物理力学岩石参数及其相内变异性进行空间分辨研究。所提出的方法学方法特别适合于EDZ的时变监测，因为测量结果无损且不会改变岩体的实际状态。这样就可以对水力压裂和机械压裂孔径，压裂表面粗糙度以及物理力学岩石参数及其相内变异性进行空间分辨研究。所提出的方法学方法特别适合于EDZ的时变监测，因为测量结果无损且不会改变岩体的实际状态。这样就可以对水力压裂和机械压裂孔径，压裂表面粗糙度以及物理力学岩石参数及其相内变异性进行空间分辨研究。