Long term behavior of hydrogeological structures associated with faulting: An example from the deep crystalline rock in the Mizunami URL, Central Japan
Long term behavior of hydrogeological structures associated with faulting: An example from the deep crystalline rock in the Mizunami URL, Central Japan
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DOI：
10.1016/j.enggeo.2016.04.026
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发表时间：
2016-06-24
影响因子：
7.4
通讯作者：
Yuguchi, Takashi
中科院分区：
文献类型：
--
作者：
Ishibashi, Masayuki;Yoshida, Hidekazu;Yuguchi, Takashi
在结晶岩石（如花岗岩）中，断层（损伤区）周围的断裂带可以充当重要的运输通道，因为断裂网络系统可能会增加活动断层周围损伤区的渗透性。了解破坏带沿着较小规模断层的特征和长期行为，对于造山带深岩体地下设施的安全评估非常重要，例如，高放射性废物处置设施。因此，本文描述了一个损害区的特点和长期行为的水文地质结构与断层在地下环境中的基础上的地质和水力调查结果300和500米以下的米祖伊地下研究实验室，日本中部。详细的钻孔和廊道壁调查显示了受损区及其周围的裂缝、裂缝填充物、主要裂缝方向、地下水流入点和水力透射率的分布。研究结果表明，水文地质构造的发育可分为三个阶段。第一阶段为背景裂缝的形成，背景裂缝是花岗岩体温度降低后，经历韧-脆性转变，在脆性变形条件下形成裂缝。第二个阶段是形成一个损害区和相应的增加，在水力渗透率的结果，形成相对较小的裂缝与断层。第三阶段是由于地下水通过破坏区渗透，降低了该区域的水力渗透性，形成裂缝填充物。在第三阶段晚期，松散的粘土质填充物形成于与断层相关的大裂缝中，导致断层周围损害带中裂缝的渗透性降低。这些结果强调了了解造山带岩体的发展阶段以评估断裂作用的重要性。(C)© 2016 Elsevier B. V.版权所有。
Fracture zones around faults (damage zones) in crystalline rocks such as granite can act as significant transport pathways because the permeability of damage zones around active faults will likely be increased by the fracture network system. Understanding the characteristics and long-term behavior of damage zones along smaller scale faults is important for the safety assessment of deep underground facilities in the plutons of an orogenic belt; for example, facilities for the disposal of high-level radioactive waste. Therefore, this paper describes the features of a damage zone and the long-term behavior of its hydrogeological structures associated with faulting in an underground environment based on the results of geological and hydraulic investigations 300 and 500 m below ground level at the Mizunami Underground Research Laboratory, Central Japan. Detailed borehole and gallery wall investigations show the distributions of fractures, fracture fillings, predominant fracture orientations, groundwater inflow points, and hydraulic transmissivity in and around a damage zone. The results indicate that there are three stages in the development of hydrogeological structures. The first stage is the formation of background fractures that formed after the temperature of granitic plutons decreased through the ductile-brittle transition, forming fractures under brittle deformation conditions. The second stage is the formation of a damage zone and corresponding increase in hydraulic permeability as a result of the formation of relatively small fractures associated with faulting. The third stage is the formation of fracture fillings because of the infiltration of groundwater through the damage zone, decreasing the hydraulic permeability of the zone. In the late third stage, unconsolidated clayey fillings form in the large fractures associated with faulting resulting in decreased permeability of the fractures in the damage zone around the fault. These results underline the importance of understanding the development stages to evaluate the effect of faulting in orogenic belt plutons. (C) 2016 Elsevier B.V. All rights reserved.