Investigating the effects of specimen diameter on the relationships between mechanical and physical properties of limestone

Engineering applications, either on or within rock bodies, typically require detailed characterizations of rock physical and mechanical properties, as both properties affect the design process and construction phase and are also related to safety and sustainability of structures. Various in-situ and laboratory tests have been used to quantify rock properties. However, the tests are expensive, time consuming and require high quality test samples, especially for laboratory tests. Additionally, available core samples may not meet test standards, which require about 54 mm (NX size) core, as suggested by the American Society for Testing and Materials (ASTM) and the International Society of Rock Mechanics (ISRM). This study aims to investigate the effects of core sample diameter on the relationships between mechanical and physical properties of rock, using the example of limestone as a test material. 190 limestone core samples were prepared in five different diameters: 24.94, 38.07, 47.7, 53.99 (NX) and 63.16 mm. Uniaxial compressive strength (UCS), diametrical and axial point load index (PLI_D-A), indirect tensile strength (ITS), Schmidt hammer (SHV), natural unit weight (γ_n), specific gravity (G_s), water content (w_c) and porosity (n) tests were performed on these core samples. The results indicate that sample diameter clearly affects the relationships between mechanical and physical properties of limestone rock, leading to broad measurement variations for most tests. Substantial agreement was found between this study and previous studies of NX size samples of limestone.