An improved method to calculate the rock brittleness index PEECR based on linear energy storage law
Fengqiang Gong*, Yiru Zuo, Song Luo, Yunliang Wang
Deep Resources Engineering. 2024, 1(1): 100005. 
doi.org10.1016j.deepre.2024.100005.pdf
Abstract: Thepeak elastic strain energy consumption ratio (PEECR) is a rock brittleness index proposed by Gong and Wang. In the present study, based on the linear energy storage law of rock under triaxial compression, a new method was proposed to calculate the PEECR. The PEECR uses a simplified method to calculate the peak elastic strain energy. To solve this problem accurately, triaxial cyclic loading-unloading compression tests were carried out on shale. Strain energy parameters were calculated from the test curves. The results show that there is a linear relationship between the elastic strain energy and input strain energy, indicating that the linear energy storage law in rock is applicable to triaxial compression state. The universality of the linear energy storage law of rock under triaxial compression is also verified by the data in the published literature. Then, the peak elastic strain energy can be accurately determined using the linear energy storage law, and the PEECR is improved based on this. Finally, the PEECR and the improved PEECR were compared using the triaxial cyclic loading-unloading compression tests on three rocks (shale, red sandstone and granite), and the improved PEECR was compared with 11 existing energy-based brittleness indexes. The results show that the improved PEECR can further reflect the rock brittleness more accurately.
Highlights:
• The linear energy storage law is applicable to rock under triaxial compression.
• The universality of linear energy storage law under triaxial compression is verified according to published test data.
• The peak elastic strain energy of rock can be accurately calculated using linear energy storage law.
• An improved method to calculate the rock brittleness index PEECR was presented.
• The improved rock brittleness index PEECR can judge rock brittleness scientifically.
Keywords: Rock brittleness index; Linear energy storage law; Peak elastic strain energy; Triaxial cyclic loading-unloading compression test
Cite: Gong, F.Q.; Zuo, Y.R.; Luo, S.; Wang, Y.L., An improved method to calculate the rock brittleness index PEECR based on linear energy storage law. Deep Resources Engineering 2024, 1 (1): 100005. https://doi.org/10.1016/j.deepre.2024.100005
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