Morphological Characteristics and Depth Distribution of Fractures in Crystalline Rock: A Case Study in Central Korea; 결정질 암반 내 단열의 형태학적 특성 및 심도별 분포 연구: 한국 중부지역 사례

초록

Ensuring the long-term isolation of radioactive nuclides is essential when constructing deep geolo gical repositories for high-level radioactive waste disposal. This study analyzed the morphological characteristics and depth distributions of fractures within biotite granite in central Korea based on drill-core samples obtained to a depth of 1,000 m. The fractures were categorized into single open fractures, single closed fractures, fractured zones, and fault zone fractures. Open fractures are charac terized by euhedral minerals (calcite, pyrite) and pore spaces, suggesting recent tectonic activity and providing potential pathways for groundwater. Closed fractures, filled completely by minerals, restrict fluid flow but could potentially be reactivated as a result of long-term geological change or anthro pogenic disturbance. Fractured zones and fault zones affect the hydrogeological flow and mechanical stability as a result of extensive rock fragmentation and alteration. In the core, fracture density increased down to ~400 m depth, after which it decreased rapidly. Rock quality designation (RQD) and average core length analyses indicated localized fractured zones at certain depths, highlighting the necessity of additional engineered barriers for repository safety. Fracture dip angle analysis revealed the dominance of low-angle (0–30°) fractures, with local increases in the proportion of high-angle (60–90°) fractures, suggesting localized tectonic influences. The results enhance our understanding of fracture evolution and hydrogeological behavior in crystalline rock, providing essential baseline data for site selection and safety assessments of high-level radioactive waste disposal repositories.

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