A New Brittleness Index Considering Radial Strain Energy Dissipation

Brittleness index is a significant mechanical parameter of rocks, widely applied in various geotechnical engineering. However, existing methods for evaluating brittleness indices have their limitations. In this study, we analyzed the energy evolution characteristics before and after peak stress in both radial and axial directions and proposed a new brittleness index considering radial strain energy evolution. The proposed method was validated through experiments. The results indicate that as confining pressure increases, rock brittleness gradually decreases. The widely used rock strength-based, elastic parameter-based, and modulus-based brittleness indices fail to reflect this trend. Only energy-based brittleness indices and the new brittleness index proposed in this paper align with this trend. However, existing energy-based indices do not consider radial energy evolution. For rocks with similar axial energy evolution characteristics but significant radial energy evolution differences, the energy-based brittle index will give the same brittleness index, which fails to evaluate brittleness characteristics accurately. The brittleness index proposed in this paper can provide accurate value for brittleness index and objective evaluations. Therefore, this new method in this study is more precise and exhibits significant advantages, compared with other mentioned brittleness index evaluation methods.