Fundamental Study of the Geological Disposal of High-Level Nuclear Waste

多屏障概念现已成为大多数国家地质处置方案的支柱。多屏障系统的制造组件构成工程屏障系统（E.B.S）。EBS的设计受到建造处置库的深层地质环境的制约。在这样的环境中，地下水正在减少，流量很小。工程屏障系统由玻璃化废物、外包装和缓冲材料组成。选择的缓冲材料具有非常低的渗透性，因此在EBS中实际上不会发生平流。但是，施工、运营和关闭活动将在对周围围岩地质环境的干扰最小的情况下进行。在施工过程中和施工结束后，准确掌握地质环境至关重要。作者提出的基于细观力学的连续介质（MBC）理论可以反映节理的密度、取向和连通性以及节理的性质。本文采用MBC分析方法对排土洞开挖过程进行了分析，并通过分析讨论了排土洞周围环境的变化，同时考虑了岩体中的节理，从数值结果可以看出：（1）初始应力方向、节理密度及其组合对排土洞围岩的力学行为有很大影响;（2）排土洞的形状或大小对节理变形有影响。（3）隧道开挖改变了渗透性等地质环境。（4）高放废物处置场建设前的数值模拟结果给出了高放废物处置场洞室开挖后环境特性的大致变化。

The multi-barrier concept now forms the backbone of geological disposal programs in most countries. The manufactured components of the multi-barrier system constitute an engineered barrier system(E.B.S). The EBS design is constrained by the deep geological environment where the repository is constructed. In such an environment, groundwater is reducing and fluxes are small. The engineered barrier system consists of the vitriaed waste, overpack and buffer material. The buffer material is selected to have a very low permeability, so that effectively no advective flow occurs in the EBS.However, the construction, operation and closure activities will be carried out with a minimum disturbance to the geological environment in surrounding host rock. It is important to grasp the geological environment accurately during and after the construction. Micromechanics-based continuum(MBC)theory proposed by authors can reflect the effects of density, orientation and connectivity of joints as well as the property of the joints. In this study, the MBC analysis is employed to analyze the excavation of disposal tunnel and the change of the environment around the tunnel is discussed with paying attention to joints in a rock mass through the analyses.From the numerical results, it is concluded that(1)The mechanical behavior of the rock mass is strongly affected by the direction of initial stresses, the joint density, and their combinations.(2)The shape or size of the disposal tunnel has an impact on the joint deformation.(3)These results lead that the excavation of a tunnel changes the geological environment such as permeability.(4)The numerical results before the construction of disposal institution of high-level radioactive waste give us the approximate changes of environmental properties in the institution after the excavation of caverns and tunnels.