Development of an Analysis Methods for the Progressive Failure of Discontinuous Solids

以高放废物处置库模型隧洞为研究对象，对开挖扰动区的变形进行了研究。试验是在平面应变条件下用人工软岩进行的。变形测量是由一个新开发的测量系统，该系统包括一个显微镜和一个高精度的X-Y工作台。试验结果表明，在应力重分布过程中形成了楔形损伤区。根据试验结果，提出了新的隧道设计概念，将楔形损伤区的形成视为隧道破坏的最终阶段。通过引入界面单元，发展了一种数值分析方法，使我们能够分析破裂区的扩展和楔形损伤区的形成。分析表明，在开挖扰动带中采用破裂带的形式，可使设计深度加深。本文还采用人造软岩进行了蠕变试验，以阐明蠕变破裂机理。在实验中，位移场的测量系统在本研究中开发的。从实验中可以看出，在高应力状态下，在与材料承载能力相当的高应力水平下，从应力状态的第一阶段开始，变形场就是不均匀的。在低应力水平下，变形场几乎是均匀的，而在高应力水平下，几乎从试验开始就观察到的剪切带直到蠕变断裂发生才形成。从试验结果可以看出，为了评价地下结构的长期安全性，建立一个基于蠕变断裂机理和局部化模式的模型是必不可少的，其中蠕变断裂是一个有待澄清的主要问题。

Deformation in excavation disturbed zone is investigated by a model tunnel of high level nuclear waste repository. The experiment is conducted using artificial soft rock under a plane strain condition. The deformation is measured by a newly developed measurement system which consists of a microscope and a high precision X-Y stage. From the experiment, it is clarified that a wedge shaped damaged zone is formed during the course of stress redistribution. Taking into account the result of the experiment new tunnel design concept is proposed, in which the formation of the wedge shaped damaged zone is considered to be the final stage of tunnel breakage. A numerical analysis method is developed by introducing an interface element which enables us to analyze propagation of rupture zone and the formation of the wedge shaped damaged zone. From the analysis, it is shown that the design depth is deepened by adopting a formation of rapture zone in the excavation disturbed zone. In the present study, creep experiment is also conducted using artificial soft rock, in order to clarify the mechanism of creep rapture. In the experiment, displacement field is measured by the measurement system developed in the present study. From the experiment, the deformation field is heterogeneous from the very first stage of stress state, in the case of high state, in the case of high stress level which is comparable with the capacity of the material. On the contrary, in the cased of low stress level, the deformation field is almost homogeneous and the shear band which is observed almost from the beginning of a test in the case of high stress level is not formed until the creep rapture takes place. From the experiment, it is clarified that the development of a model based on the mechanism of creep rapture and localization mode is indispensable in order to evaluate long term safety of underground structures, in which the creep rupture becomes a dominant problem to be clarified.