With the economic development and technological advancement around the world, many people are now considering the development of underground space engineering such as underground buildings, underground parking lots, river crossing tunnels, subways, and deep mine mining. Underground rock masses belong to a class of discontinuous and heterogeneous anisotropic brittle materials. The crustal movement of millions of years makes the internal structure extremely complex. Brittleness is a key mechanical feature of rock and is critical to a variety of engineering practices. Based on the energy evolution of rock failure process, the evolution law of strain energy such as pre-peak dissipation energy and post-peak fracture energy during the transformation from plastic deformation to brittle fracture under compression is analyzed. Combining these two energies, the brittleness evaluation index which can comprehensively reflect the mechanical characteristics before and after rock failure is established. The brittleness characteristics of different rock materials under different confining pressures are evaluated. The fracture morphology of shale under different bedding angles is analyzed. The results show that the brittleness evaluation index established in this paper can simultaneously reflect the difficulty of brittle fracture and the strength of brittleness. It can not only describe the brittleness of different rock materials with confining pressure, but also describe the law of change for shale brittleness index based on bedding dip.

Yingying Fan. Examination on Brittleness Evaluation Index Based on Energy Evolution of Rock Failure Process. International Journal of Engineering Technology and Construction (2020), Vol. 1, Issue 1: 17-28. https://doi.org/10.38007/IJETC.2020.010102.

[1] Kivi, I. R., Ameri, M., & Molladavoodi, H. (2018) “Shale Brittleness Evaluation Based on Energy Balance Analysis of Stress-Strain Curves”, Journal of Petroleum Science & Engineering, 167(11), pp.23 https://doi.org/10.1016/j.petrol.2018.03.061

[2] Ai, C, Zhang, J, Li, Y. W, Zeng, J, Yang, X. L, & Wang, J. G. (2016) “Estimation Criteria for Rock Brittleness Based on Energy Analysis During the Rupturing Process”, Rock Mechanics and Rock Engineering, 49(12), pp.4681-4698. https://doi.org/10.1007/s00603-016-1078-x

[3] Zhang, J, Chi, A. I, Yuwei, L. I, Zeng, J, & Qiu, D. (2017) “Brittleness Evaluation Index Based on Energy Variation in the Whole Process of Rock Failure”, Chinese Journal of Rock Mechanics & Engineering, 36(6), pp.25.

[4] Wang, X, Ge, H, Wang, D, Wang, J, & Chen, H. (2017) “A Comprehensive Method for the Fracability Evaluation of Shale Combined with Brittleness and Stress Sensitivity”, Journal of Geophysics & Engineering, 14(6), pp.10-25. https://doi.org/10.1088/1742-2140/aa7ffd

[5] Lizcano-Hernández, Edgar G, Nicolás-López, Rubén, Valdiviezo-Mijangos, O. C, & Meléndez-Martínez, Jaime. (2017) “Estimation of Brittleness Indices for Pay Zone Determination in a Shale-Gas Reservoir by Using Elastic Properties Obtained from Micromechanics”, Journal of Geophysics and Engineering, 19(8), pp.110-225

[6] Chen, G, Jiang, W, Sun, X, Zhao, C, & Qin, Chang’An. (2019) “Quantitative Evaluation of Rock Brittleness Based on Crack Initiation Stress and Complete Stress–Strain Curves”, Bulletin of Engineering Geology and the Environment, 25(11), pp.95

[7] Tan, W. H., Ba, J, Guo, M. Q., Li, H., Zhang, L., & Yu, T. (2018) “Brittleness Characteristics of Tight Oil Siltstones”, Applied Geophysics, 15(2), pp.175-187. https://doi.org/10.1007/s11770-018-0680-y

[8] Qamar, Y, Qizhen, D, Sohail, G. M., & Atif, I. (2018) “Fracturing Index-Based Brittleness Prediction from Geophysical Logging Data: Application to Longmaxi Shale”, Geomechanics and Geophysics for Geo-Energy and Geo-Resources, 16(4), pp.153-166. https://doi.org/10.1007/s40948-018-0088-4

[9] Li, Z, Li, L, Li, M, Zhang, L., Zhang, Z., & Huang, B. (2018) “A Numerical Investigation on the Effects of Rock Brittleness on the Hydraulic Fractures in the Shale Reservoir”, Journal of Natural Gas Science & Engineering, 50(10), pp.22-32. https://doi.org/10.1016/j.jngse.2017.09.013

[10] Zhou, X. P., Lian, Y. J, Wong, L. N. Y., & Berto, F. (2018) “Understanding the Fracture Behavior of Brittle and Ductile Multi-Flawed Rocks by Uniaxial Loading by Digital Image Correlation”, Engineering Fracture Mechanics, 183(3), pp.199-210. https://doi.org/10.1016/j.engfracmech.2018.06.007

[11] Jadoon, Q. K, Roberts, E. M, Henderson, R. A, Blenkinsop, T. G, & Wust, R. A. J. (2018) “Mineralogical Variability of the Permian Roseneath and Murteree Shales from the Cooper Basin, Australia: Implications for Shale Properties and Hydrocarbon Extraction”, Journal of Petroleum Science and Engineering, 73(9), pp.98-112. https://doi.org/10.1016/j.petrol.2017.12.022

[12] Hernandez-Uribe, L. A, Aman, M., & Espinoza, D. N. (2017) “Assessment of Mudrock Brittleness with Micro-Scratch Testing”, Rock Mechanics & Rock Engineering. 10(7), pp.17. https://doi.org/10.1007/s00603-017-1279-y