An energy-based method for uniaxially compressed rocks and its implication

Abstract

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 σ ≥ 0.9σc (σ denotes stress and σc 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 σ < 0.9σc and six unloading stress levels were designated for σ ≥ 0.9σc. The variations in the elastic energy density (ue), dissipative energy density (ud), and energy storage efficiency (C) for the four rock types under GCLU tests were analyzed. Based on the variation of ue when σ ≥ 0.9σc, 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 C0.9 (C at σ ≥ 0.9σc) 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.

Keywords

• Calculation method of peak energy density
• Energy evolution
• Energy storage efficiency
• Damage threshold