Abstract：The current indices used to evaluate the shale brittleness consider mostly the mechanical properties before or after the peak separately and cannot reflect the brittleness characteristics in the whole process of rock failure. In this paper，the variation of the various types of strain energy of rock materials in the process of plastic deformation to brittle fracturing was analysed based on the complete stress-strain curves. The levels of the pre-peak dissipation energy and the post-peak fracturing energy are the key factors to determine whether the brittle fracturing occurs. The brittleness estimation indices which represent comprehensively the mechanical properties of rock in pre-peak and post-peak periods were proposed by combining the pre-peak dissipation energy and the post-peak fracturing energy. The brittle characteristics of different rock materials under different confining pressures and the anisotropy of shale brittleness were evaluated with these brittleness indices. The results show that the proposed brittleness indices can simultaneously reflect the difficulty of brittle failure and the scale of brittleness and can evaluate the change of brittle characteristics under different mechanical conditions. The pre-peak dissipation energy and post-peak fracturing energy of different rock materials increase with the increase of the confining pressure. The brittleness decreases constantly with the increase of the confining pressure，but the decrease trends are different. The red sandstone and shale show the transformation of brittleness-plasticity at low and high confining pressures，while the granite has the strong brittleness in the whole process of the confining pressure increasing. The brittleness of shale is anisotropic. The brittleness of shale specimens with different inclination angles of bedding plane has significant difference. The shale brittleness shows a transition process of stable，increase to decrease as the inclination angle of bedding planes ? increases. When ? = 0°，the degree of brittleness of shale is stronger than that of ? = 90°. When ? = 60°，shale has the weakest brittleness and shows the plastic characteristic.
张 军，艾 池，李玉伟，曾 佳，仇德智. 基于岩石破坏全过程能量演化的脆性评价指数[J]. 岩石力学与工程学报, 2017, 36(6): 1326-1340.
ZHANG Jun，AI Chi，LI Yuwei，ZENG Jia，QIU Dezhi. Brittleness evaluation index based on energy variation in the whole process of rock failure. , 2017, 36(6): 1326-1340.
[1] 蒋裕强，董大忠，漆 麟，等. 页岩气储层的基本特征及其评价[J]. 天然气工业，2010，30(10)：7–12.(JIANG Yuqing，DONG Dazhong， QI Lin，et al. Basic features and evaluation of shale gas reserviors[J]. Nature Gas Industry，2010，30(10)：7–12.(in Chinese))
[2] WANG F P，REED R M. Pore networks and fluid flow in gas shale[R]. New Orleans：Society of Petroleum Engineers，2009.
[3] MATT B，BILL G. Special techniques tap shale gas[J]. Exploration and Production in Hart Energy，2007，80(3)：89–93.
[4] 李庆辉，陈 勉，WANG F P，等. 工程因素对页岩气产量的影响——以北美Haynesville页岩气藏为例[J]. 天然气工业，2012，32(4)：54–59.(LI Qinghui，CHEN Mian，WANG F P，et al. Influences of engineering factors on shale gas production—take the Haynesville shale gas reservoir in North America for example[J]. Journal of Natural Gas Industry，2012，32(4)：54–59.(in Chinese))
[5] BECK D A，BRADY B H G. Evaluation and application of controlling parameters for seismic events in hard-rock mines[J]. International Journal of Rock Mechanics and Mining Sciences，2002，39(5)：633–642.
[6] 张镜剑，傅冰骏. 岩爆及其判据和防治[J]. 岩石力学与工程学报，2008，27(10)：2 034–2 042.(ZHANG Jingjian，FU Bingjun. Rock burst and its criteria and control[J]. Chinese Journal of Rock Mechanics and Engineering，2008，27(10)：2 034–2 042.(in Chinese))
[7] MORLEY A. Strength of materials[M]. London：Longmans Green and Company，1944：71–72.
[8] HETENYI M. Handbook of experimental stress analysis[M]. New York：John Wiley，1966：23–25.
[9] RAMSAY J G. Folding and fracturing of rocks[M]. London：McGraw-Hill，1967：44–47.
[10] OBERT L，DUVALL W I. Rock mechanics and the design of structures in rock[M]. New York：John Wiley，1967：78–82.
[11] ANDREEV G E. Brittle failure of rock material-test results and constitutive models[M]. Rotterdam：A. A. Balkema，1995：123–128.
[12] GOKTAN R M，GUNES Y N. A new methodology for the analysis of the relationship between rock brittleness index and drag pick cutting efficiency[J]. The South African Institute of Mining and Metallurgy，2005，105：727–734.
[13] 李庆辉，陈 勉，金 衍，等. 页岩气储层岩石力学特性及脆性评价[J]. 石油钻探技术，2012，40(4)：17–22.(LI Qinghui，CHEN Mian，JIN Yan，et al. Rock mechanical properties and brittleness evaluation of shale gas reservoir[J]. Petroleum Drilling Techniques，2012，40(4)：17–22.(in Chinese))
[14] HNODA H，SANADA Y. Hardness of coal[J]. Fuel，1956，35：451.
[15] HUCKA V，DAS B. Brittleness determination of rocks by different methods[J]. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts，1974，11(10)：389–392.
[16] BISHOP A W. Progressive failure with special reference to the mechanism causing it[C]// Proceedings of the Geotechnical Conference. Oslo，Norway：[s.n.]，1967：142–150.
[17] 周 辉，孟凡震，张传庆，等. 基于应力–应变曲线的岩石脆性特征定量评价方法[J]. 岩石力学与工程学报，2014，33(6)：1 114–1 122. (ZHOU Hui，MENG Fanzhen，ZHANG Chuanqing，et al. Quantitative evaluation of rock brittleness based on stress-strain curve[J]. Chinese Journal of Rock Mechanics and Engineering，2014，33(6)：1 114–1 122. (in Chinese))
[18] RICKMAN R，MULLEN M，PETRE E，et al. A practical use of shale petrophysics for stimulation design optimization：All shale plays are not clones of the Barnett Shale[R]. Denver，Colorado，USA：Society of Petroleum Engineers，2008.
[19] JARVIE D M，HILL R J，RUBLE T E，et al. Unconventional shale-gas systems：the mississippian barnett shale of north-central texas as one model for thermogenic shale-gas assessment[J]. The American Association of Petroleum Geologists，Bulletin，2007，91(4)：475–499.
[20] ALTINDAG R，GUNEY A. Predicting the relationships between brittleness and mechanical properties(UCS，TS and SH) of rocks[J]. Scientific Research and Essays，2010，5(16)：2 107–2 118.
[21] MIKAEIL R，ATAEI M，YOUSEFI R. Correlation of production rate of ornamental stone with rock brittleness indexes[J]. Arabian Journal of Geosciences，2011，6(1)：115–121.
[22] 王 宇，李 晓，武艳芳，等. 脆性岩石起裂应力水平与脆性指标关系探讨[J]. 岩石力学与工程学报，2014，33(2)：264–275.(WANG Yu，LI Xiao，WU Yanfang，et al. Research on relationship between crack initiation stress level and brittleness indices for brittle rocks[J]. Chinese Journal of Rock Mechanics and Engineering，2014，33(2)：264–275.(in Chinese))
[23] HAJIABDOLMAJID V，KAISER P. Brittleness of rock and stability assessment in hard rock tunneling[J]. Tunnelling and Underground Space Technology，2003，18：35–48.
[24] AUBERTIN M，Gill D E. Use méthodologie d'évaluation du potentile de coups de terrain dans les mines d'Abitibi[C]// Proceedings Colloque sur le Controle de Terrain(AMMQ). [S. l.]：[s. n.]，1988：47–77.
[25] BATOUGINA I M，PETOUKHOV I M，VINOKUR B S，et al. Methodological instructions for rock burst prophylaxis accounting the deposit geodynamics[M]. Leningrad：VNIMI，1983：132–135.
[26] BARON L I. Determination of properties of rocks[M]. Moscow：Gozgotekhizdat，1962：231–233.
[27] KIDYBINSKI A. Bursting liability indices of coal[J]. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts，1981，18(4)：295–304.
[28] TARASOV B G，POTVIN Y. Universal criteria for rock brittleness estimation under triaxial compression[J]. International Journal of Rock Mechanics and Mining Sciences，2013，59(4)：57–69.
[29] TARASOV B G，RANDOLPH M F. Superbrittleness of rocks and earthquake activity[J]. International Journal of Rock Mechanics and Mining Sciences，2011，48(6)：888–898.
[30] 杨圣奇，徐卫亚，苏承东. 大理岩三轴压缩变形破坏与能量特征研究[J]. 工程力学，2007，24(1)：136–142.(YANG Shengqi，XU Weiya，SU Chengdong. Study on the deformation failure and energy properties of marble specimen under triaxial compression[J]. Engineering Mechanics，2007，24(1)：136–142.(in Chinese))
[31] 张国凯，李海波，夏 祥，等. 岩石单轴压缩下能量与损伤演化规律研究[J]. 岩土力学，2015，36(增1)：94–100.(ZHANG Guokai，LI Haibo，XIA Xiang，et al. Research on energy and damage evolution of rock under uniaxial compression[J]. Rock and Soil Mechanics，2015，36(Supp.1)：94–100.(in Chinese))
[32] 谢和平，彭瑞东，鞠 杨. 岩石变形破坏过程中的能量耗散分析[J]. 岩石力学与工程学报，2004，23(21)：3 565–3 570.(XIE Heping，PENG Ruidong，JU Yang. Energy dissipation of rock deformation and fracture[J]. Chinese Journal of Rock Mechanics and Engineering，2004，23(21)：3 565–3 570.(in Chinese))
[33] 尤明庆，华安增. 岩石岩样单轴压缩的破坏形式与承载能力的降低[J]. 岩石力学与工程学报，1998，17(3)：292–296.(YOU Mingqing，HUA Anzeng. Fracture of rock specimen and decrement of bearing capacity in uniaxial compression[J]. Chinese Journal of Rock Mechanics and Engineering，1998，17(3)：292–296.(in Chinese))
[34] 张志镇，高 峰. 单轴压缩下红砂岩能量演化实验研究[J]. 岩石力学与工程学报，2012，31(5)：953–961.(ZHANG Zhizhen，GAO Feng. Experimental research on energy evolution of red sandstone samples under uniaxial compression[J]. Chinese Journal of Rock Mechanics and Engineering，2012，31(5)：953–961.(in Chinese))
[35] 张志镇. 岩石形破坏过程中的能量演化机制[博士学位论文][D]. 北京：中国矿业大学，2013.(ZHANG Zhizhen. Energy evolution mechanism during rock deformation and failure[Ph. D. Thesis][D]. Beijing：China University of Mining and Technology，2013.(in Chinese))
[36] 谢和平，彭瑞东，鞠 杨，等. 岩石破坏的能量分析初探[J]. 岩石力学与工程学报，2005，24(15)：2 603–2 608.(XIE Heping，PENG Ruidong，JU Yang，et al. On energy analysis of rock failure[J]. Chinese Journal of Rock Mechanics and Engineering，2005，24(15)：2 603– 2 608.(in Chinese))
[37] 谢和平，鞠 杨，黎立云，等. 岩体变形破坏过程的能量机制[J]. 岩石力学与工程学报，2008，27(9)：1 729–1 739.(XIE Heping，JU Yang，LI Liyun，et al. Energy mechanism of deformation and failure of rock masses[J]. Chinese Journal of Rock Mechanics and Engineering，2008，27(9)：1 729–1 739.(in Chinese))
[38] 陈 昀，金 衍，陈 勉. 基于能量耗散的岩石脆性评价方法[J]. 力学学报，2015，47(6)：984–992.(CHEN Yun，JIN Yan，CHEN Mian. A rock brittleness evaluation method based on energy dissipation[J]. Chinese Journal of Theoretical and Applied Mechanics，2015，47(6)：984–992.(in Chinese))
[39] 苏承东，李怀珍，张 盛，等. 应变速率对大理岩力学特性影响的实验研究[J]. 岩石力学与工程学报，2013，32(5)：943–950.(SU Chengdong，LI Huaizhen，ZHANG Sheng，et al. Experimental investigation on effect of strain rate on mechanical characteristics of marble[J]. Chinese Journal of Rock Mechanics and Engineering，2013，32(5)：943–950.(in Chinese))
[40] 张志镇，高 峰，高亚楠，等. 高温后花岗岩应力脆性跌落系数的实验研究[J]. 实验力学，2010，25(5)：589–596.(ZHANG Zhizhen，GAO Feng，GAO Yanan，et al. Experimental study of brittle stress drop coefficient of granite endured high temperature[J]. Journal of Experimental Mechanics，2010，25(5)：589–596.(in Chinese))
[41] 张志镇，高 峰. 单轴压缩下岩石能量演化的非线性特性研究[J]. 岩石力学与工程学报，2012，31(6)：1 198–1 202.(ZHANG Zhizhen， GAO Feng. Research on nonlinear characteristics of rock energy evolution under uniaxial compression[J]. Chinese Journal of Rock Mechanics and Engineering，2012，31(6)：1 198–1 202.(in Chinese))
[42] 张志镇，高 峰. 3种岩石能量演化特征的实验研究[J]. 中国矿业大学学报，2015，44(3)：416–422.(ZHANG Zhizhen，GAO Feng. Experimental investigations on energy evolution characteristics of coal，sandstone and granite during loading process[J]. Journal of China University of Mining and Technology，2015，44(3)：416–422.(in Chinese))
[43] 张志镇，高 峰. 受载岩石能量演化的围压效应研究[J]. 岩石力学与工程学报，2015，34(1)：1–10.(ZHANG Zhizhen，GAO Feng. Confining pressure effect on rock energy[J]. Chinese Journal of Rock Mechanics and Engineering，2015，34(1)：1–10.(in Chinese))
[44] TARASOV B G. Super-brittleness of rocks at high confining pressure[C]// Deep Mining 2010 of Australian Centre for Geomechanics. Perth：[s.n.]，2010：119–133.
[45] TARASOV B G. Universal scale of brittleness for rocks failed at compression[C]// The 13th International Conference of the International Association for Computer Methods and Advances in Geomechanics. Sydney：[s.n.]，2011：669–673.
[46] RECHES Z. Mechanisms of slip nucleation during earthquakes[J]. Earth and Planetary Science Letters，1999，170：475–486.
[47] RECHES Z，LOCKNER D A. Nucleation and growth of faults in brittle rocks[J]. Journal of Geophysical Research Atmospheres，1994，99(B9)：18 159–18 173.
[48] COX S J D，SCHOLZ C H. On the formation and growth of faults：an experimental study[J]. Journal of Structural Geology，1988，10：413–430.
[49] PENG S，JOHNSON A M. Crack growth and faulting in cylindrical specimens of Chelmsford granite[J]. International Journal of Rock Mechanics and Mining Sciences，1972，9(1)：37–86.
[50] KING G C P，SAMMIS C G. The mechanisms of finite brittle strain[J]. Pure and Applied Geophysics，1992，138(4)：611–640.
[51] ORTLEPP W D. Rock fracture and rock bursts：an illustrative study[M]. Johannesburg：South African Institute of Mining and Metallurgy，1997：98–100.
[52] ASWEGEN G V. Ortlepp Shears – dynamic brittle shears of S.A. goldmines[C]// Conference：First Southern Hemisphere International Rock Mechanics Symposium. Perth：[s.n.]，2008：1–9.
[53] 左建平，黄亚明，熊国军，等. 脆性岩石破坏的能量跌落系数研究[J]. 岩土力学，2014，35(2)：321–327.(ZUO Jianping，HUANG Yaming，XIONG Guojun，et al. Study of energy-drop coefficient of brittle rock failure[J]. Rock and Soil Mechanics，2014，35(2)：321–327.(in Chinese))
[54] 苏为华. 多指标综合评价理论与方法问题研究[博士学位论文][D]. 厦门：厦门大学，2000.(SU Weihua. Research on the theory and method of multi index comprehensive evaluation[Ph. D. Thesis][D]. Xiamen：Xiamen University，2000.(in Chinese))
[55] 苏为华. 我国多指标综合评价技术与应用研究的回顾与认识[J]. 统计研究，2012，29(8)：98–107.(SU Weihua. Review and recognition on the research of multi-indicators comprehensive evaluation in China[J]. Statistical Research，2012，29(8)：98–107.(in Chinese))
[56] 孙建孟，韩志磊，秦瑞宝，等. 致密气储层可压裂性测井评价方法[J]. 石油学报，2015，36(1)：74–80.(SUN Jianmeng，HAN Zhilei，QIN Ruibao，et al. Log evaluation method of fracturing performance in tight gas reservoir[J]. Acta Petrolei Sinica，2015，36(1)：74–80.(in Chinese))
[57] GUO Z Q，CHAPMAN M，LI X Y. A shale rock physics model and its application in the prediction of brittleness index，mineralogy，and porosity of the Barnett Shale[R]. [S.l.]：[s.n.]，2012.
[58] MARSH H W，WEN Z，HAU K T. Structural equation models of latent interactions：evaluation of alternative estimation strategies and indicator construction[J]. Psycho Logical Methods，2004，9(3)：275–300.
[59] 周 辉，孟凡震，卢景景，等. 硬岩裂纹起裂强度和损伤强度取值方法探讨[J]. 岩土力学，2015，35(4)：913–925.(ZHOU Hui，MENG Fanzhen，LU Jingjing，et al. Discussion on methods for calculating crack initiation strength and crack damage strength for hard rock[J]. Rock and Soil Mechanics，2015，35(4)：913–925.(in Chinese))
[60] 李庆辉，陈 勉，金 衍，等. 页岩脆性的室内评价方法及改进[J]. 岩石力学与工程学报，2012，31(8)：1 680–1 689.(LI Qinghui，CHEN Mian，JIN Yan，et al. Indoor evaluation method for shale brittleness and improvement[J]. Chinese Journal of Rock Mechanics and Engineering，2012，31(8)：1 680–1 689.(in Chinese))
[61] 李庆辉，陈 勉，金 衍，等. 含气页岩破坏模式及力学特性的实验研究[J]. 岩石力学与工程学报，2012，31(增2)：3 763–3 773.(LI Qinghui，CHEN Mian，JIN Yan，et al. Experimental research on failure modes and mechanical behaviors of gas-bearing shale[J]. Chinese Journal of Rock Mechanics and Engineering，2012，31(Supp.2)：3 763–3 773.(in Chinese))
2017, Vol. 36 
