The growth of faults and fracture networks in a mechanically evolving, mechanically stratified rock mass: a case study from Spireslack Surface Coal Mine, Scotland
The growth of faults and fracture networks in a mechanically evolving, mechanically stratified rock mass: a case study from Spireslack Surface Coal Mine, Scotland
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DOI：
10.5194/se-11-2119-2020
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发表时间：
2020-11
期刊：
影响因子：
3.4
通讯作者：
Billy J. Andrews;Z. Shipton;R. Lord;Lucy McKay
中科院分区：
文献类型：
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作者：
Billy J. Andrews;Z. Shipton;R. Lord;Lucy McKay
抽象的。断层结构和裂缝网络演化（以及由此产生的整体水力特性）高度依赖于结构发育时岩石的力学特性。本文研究了机械分层和先存构造对走滑断层和裂缝网络演化的作用。对苏格兰 Spireslack 露天煤矿暴露得非常好的河流-三角洲岩性进行的详细测绘揭示了断层的两个阶段，具有最初的左旋剪切感和后来的右旋剪切感，以及持续的断层前、同断层和断层后节理组。我们发现断层带内部结构取决于断层是否自并置或切割多种岩性、促进地床旋转和断层核透镜体形成的页岩层的存在以及断层时节理和煤割理的方向。在持续变形过程中，裂缝的胶结集中在裂缝网络连接最紧密的地方。这导致了反直觉的结果，即网络中裂缝密度最高的部分通常具有最低的开放裂缝连通性。为了评估变形岩体的最终整体水力特性，了解变形事件的相对时间、同时或随后的胶结作用以及对整体网络连通性的相互关联的影响至关重要。
Abstract. Fault architecture and fracture network evolution (and resulting bulk hydraulic properties) are highly dependent on the mechanical properties of the rocks at the time the structures developed. This paper investigates the role of mechanical layering and pre-existing structures on the evolution of strike–slip faults and fracture networks. Detailed mapping of exceptionally well exposed fluvial–deltaic lithologies at Spireslack Surface Coal Mine, Scotland, reveals two phases of faulting with an initial sinistral and later dextral sense of shear with ongoing pre-faulting, syn-faulting, and post-faulting joint sets. We find fault zone internal structure depends on whether the fault is self-juxtaposing or cuts multiple lithologies, the presence of shale layers that promote bed-rotation and fault-core lens formation, and the orientation of joints and coal cleats at the time of faulting. During ongoing deformation, cementation of fractures is concentrated where the fracture network is most connected. This leads to the counter-intuitive result that the highest-fracture-density part of the network often has the lowest open fracture connectivity. To evaluate the final bulk hydraulic properties of a deformed rock mass, it is crucial to appreciate the relative timing of deformation events, concurrent or subsequent cementation, and the interlinked effects on overall network connectivity.