Stress field analysis: Construction of site descriptive model of underground research site in KAERI

Abstract

This study aims to integrate geological investigation data and construct a rock mechanical site descriptive model relative to site selection research for deep geological disposal of spent nuclear fuel. As preliminary research for the model construction process, a sub-divided numerical domain was introduced by adopting existing fracture zone in the site region of an underground research facility in KAERI. The spatial properties of the domain were decided based on the rock classification information of core specimens obtained from several boreholes. Stress field estimation modeling was performed using the constructed domain and the results were compared with the in-situ state of the field test. When the depth-dependent stress ratio was assigned to the model condition, it was confirmed that an appropriate stress state was ensured with the similarity of the in-situ stress along the depths. Additionally, uncertainties of the input properties in the stress estimation model were also assessed. The effect of uncertainties could be considered through a sensitivity analysis of rock mass and fracture zone properties to identify stress dependence on mechanical properties. Significant stress distribution was not indicated with a variation in the rock mass properties. However, weak fracture zone modeling induced a slightly disturbed stress in a shallow depth range. These results indicated that the uncertainty of the rock mechanical site descriptive model could be increased due to the fracture zone properties. This study is a case of prior research in Korea on the site evaluation model that is already applied in leading foreign countries related to site selection research for nuclear fuel disposal. The applicability based on the achievement of this study can be improved through consideration of derived equivalent properties of fractured rock. And more reliable results can be succeeded by assigning properly defined boundary conditions for the simulation of various geological scenarios.