(3)

To obtain the precise calculation method for the peak energy density and energy evolution properties of rocks subjected to uniaxial compression (UC) before the post-peak stage, particularly at sigma >= 0.9 sigma(c) (sigma denotes stress and sigma(c) is the peak strength), extensive UC and uniaxial graded cyclical loading-unloading (GCLU) tests were performed on four rock types. In the GCLU tests, four unloading stress levels were designated when sigma < 0.9 sigma(c) and six unloading stress levels were designated for sigma >= 0.9 sigma(c). The variations in the elastic energy density (u(e)), dissipative energy density (u(d)), and energy storage efficiency (C) for the four rock types under GCLU tests were analyzed. Based on the variation of u(e) when sigma >= 0.9 sigma(c), a method for calculating the peak energy density was proposed. The energy evolution in rock under UC condition before the post-peak stage was examined. The relationship between C-0.9 (C at sigma >= 0.9 sigma(c)) and mechanical behavior of rocks was explored, and the damage evolution of rock was analyzed in view of energy. Compared with that of the three existing methods, the accuracy of the calculation method of peak energy density proposed in this study is higher. These findings could provide a theoretical foundation for more accurately revealing the failure behavior of rock from an energy perspective. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

来源平台：JOURNAL OF ROCK MECHANICS AND GEOTECHNICAL ENGINEERING