Ultra-long-term storage of spent nuclear fuel and other waste products is most likely to be accomplished through the construction and safe closure of deep geological repositories (DGRs). Around the world, numerous countries are planning, designing and in some cases, building such repositories in sound rock between 400 and 1000 m below surface. In Ontario, Canada, both crystalline (granite, gneiss, etc.) and sedimentary (limestone) are being considered as host formations. A critical element of the host rock (the geo-barrier) is the susceptibility to excavation-induced damage and the long-term evolution of this fracture damage over the lifetime of the repository. The excavation damage zone, EDZ, can form a pathway for the migration of radionuclides from the repository, bypassing seals and internal barrier structures. The Cobourg Limestone is a candidate formation for DGR construction in Ontario, Canada. The long-term performance of this barrier rock may be controlled in part by internal structures including pseudo-bedding in the form of varying clay mineral content and an argillaceous/calcite nodular structure. Typically, geotechnical assessment, analysis and design are based on standard rock properties obtained from laboratory testing on 50–75 mm diameter samples and the occurrence (if any) of jointing. Neglected are the impacts of the internal texture within the limestone. The potential impacts of these structures on EDZ evolution are numerically explored in this paper to provide a schematic illustration of their potential importance for ultra-long-term behaviour. It is evident from this scoping study that the physical (and geological) nature of the bedding structures as well as the internal intra-bed fabric plays as significant a role in behaviour as does the nominal as-measured bulk properties.

乏核燃料和其他废物产品的超长期储存最有可能通过建造和安全关闭深层地质处置库 (DGR) 来实现。在世界范围内，许多国家正在计划、设计并在某些情况下在地表以下 400 至 1000 m 的健全岩石中建造此类储存库。在加拿大安大略省，晶体（花岗岩、片麻岩等）和沉积物（石灰岩）都被视为寄主地层。主岩（地质屏障）的一个关键因素是对开挖引起的损坏的敏感性以及在储存库的整个生命周期内这种裂缝损坏的长期演变。开挖损伤区 EDZ 可形成放射性核素从储存库迁移、绕过密封件和内部屏障结构的通道。Cobourg Limestone 是加拿大安大略省 DGR 建设的候选地层。这种屏障岩的长期性能可能部分受内部结构控制，包括不同粘土矿物含量形式的假层理和泥质/方解石结节结构。通常，岩土工程评估、分析和设计基于从实验室对 50-75 毫米直径样品和节理的出现（如果有）测试获得的标准岩石特性。被忽视的是石灰石内部结构的影响。本文以数值方式探讨了这些结构对 EDZ 演化的潜在影响，以提供它们对超长期行为的潜在重要性的示意图。