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http://dx.doi.org/10.7474/TUS.2021.31.2.125

Effect of Excavation and Thermal Stress on Slip Zone and Aperture Change Around Disposal Hole and Tunnel in Fractured Rock  

Hong, Suyeon (Department of Nuclear Safety Research, Korea Institute of Nuclear Safety)
Kwon, Saeha (Research Institute of Energy and Resources)
Min, Ki-Bok (Department of Energy Systems Engineering, Seoul National University)
Ji, Sung-Hoon (Radwaste Disposal Research Division, Korea Atomic Energy Research Institute)
Publication Information
Tunnel and Underground Space / v.31, no.2, 2021 , pp. 125-144 More about this Journal
Abstract
Deep geological disposal is one of the most prominent option for the permanent disposal of high-level radioactive waste(HLW) generated from nuclear power. There is a need for studies considering coupled thermo-hydro-mechanical behavior to assess the performance of the repository. In particular, the comprehensive analysis considering rock fracture properties and geometry is necessary. Therefore, in this study, sensitivity analyses are conducted using two-dimensional distinct element method simulator to quantitatively analyze the effects of joint angle, friction angle and stress ratio on slip zone and aperture around the disposal tunnel and hole in the fractured rocks. As a result of stress modeling after excavation, the effect of shear dilation dramatically increased as the friction angle decreased. The area where the aperture change was about 1.5 times of the initial aperture varied from 2.8 to 4.8 times, 4.3 to 10.7 times and 2.6 times to 4.2 times for the variation of joint angle, friction angle and stress ratio, respectively. The results obtained in the discrete fracture network model were similar to the uniformly jointed model, and the slip zone occurred within the region not exceeding three times of the opening radius in all models at the friction angle of 30°. As a result of modeling considering thermal stress in the disposal hole model, the aperture was closed in all models and most of the slip zone disappeared which had been caused by the excavation. This study can be used as basic data in the site selection guidelines for HLW disposal repository, and can be used for performance assessment of geological repository for HLW.
Keywords
Radioactive waste; Deep geological disposal; Aperture; Discrete fracture network; Slip zone; Discrete element method;
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