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ABSTRACT: Rocks exhibit anisotropy in various properties, including ultrasonic waves and diametrical deformation in the radial direction. While previous studies have attempted to analyze rock failure and anisotropy using several cores, the aim of this research is to evaluate the properties and anisotropic characteristics of rock materials through non-destructive experimental analysis of a single core. This analysis focuses on three physical properties: diametrical change, P-wave velocity, and compressive elastic modulus. The specimens were shaped into disks, with a diameter of 50 mm and thickness ranging from 26 to 29 mm. They were subjected to mechanical loading, ultrasonic waves, and diameter measurements in rotating radial directions to quantify anisotropic traits. These experiments revealed significant variations in diameter change, elastic modulus, and P-wave velocity across different orientations, indicating a substantial degree of anisotropy in the rock specimens. Consequently, this research performed non-destructive analysis of rock cores, characterizing physical properties, and analyzing anisotropy, confirming that the diameter and P-wave velocity maintain nearly perpendicular angles. Additionally, X-ray CT analysis has shown that rocks with lower homogeneity exhibit more pronounced anisotropy. 1. INTRODUCTION Rock anisotropy is primarily influenced by structural features such as cleavage, foliation, bedding planes, schistosity, along with various joints and fissures ranging from micro to macro in size, and is also determined by two main mechanisms when subjected to structural loads: the alignment of minerals and particles, and the arrangement of pores and microcracks, which vary based on the rock's composition (Phillips and Phillips, 1980). Rocks possess hydraulic, mechanical, thermal, dynamic, and physical properties, and these anisotropy of structural properties causes these characteristics to vary depending on the direction (Johnston and Christensen, 1995; Amadei, 1996). Understanding the importance of rock anisotropy is essential, as it directly influences different applications such as seismic wave propagation in oil and gas exploration, fault stress distribution, which is critical to earthquake preparedness, impacts the structural integrity of dams, dictates the containment of radioactive materials, affects heat extraction rates in geothermal operations, and guides excavation strategies in tunnel construction.
Kim et al. (Sun,) studied this question.