To testify the Mogi-Coulomb criterion in triaxial unloading test and based on available unloading testing data, the Mogi-Coulomb strength criterion with a linear fitting method was used in the conventional triaxial unloading tests and the true triaxial unloading tests, respectively. A comprehensive comparative analysis was presented for the related strength parameters according to the fitting results and combination of the failure characteristics of rock specimens. The results showed that the Mogi-Coulomb strength criterion has a good applicability to rock samples under conventional triaxial unloading conditions. However, under true triaxial unloading tests, even though the fitting degree is very good, the fitting parameter a is negative which leads to a negative cohesion of rock samples. This is impossible in practice. Since the Mogi-Coulomb strength criterion is based on the assumption that rock fails in shear, it cannot describe the failure of rock under true triaxial unloading conditions in which the failure modes of rocks specimens may change from shear to extensional slabbing or rock burst. Therefore, for combined shear and tensile failure processes of rocks under true triaxial unloading conditions, it is necessary to build a new strength criterion to describe its constitutive relationships, which is important for deep rock mechanics.
[1] 李建林. 卸荷岩体力学[M]. 北京: 中国水利水电出版社, 2003. Li Jianlin. Unloading rock mass mechanics[M]. Beijing: China Water & Power Press, 2003.
[2] 张春生, 陈祥荣, 侯靖, 等. 锦屏二级水电站深埋大理岩力学特性研究 深埋大理岩力学特性研究[J]. 岩石力学与工程学报, 2010, 29(10): 1999-2009. Zhang Chunsheng, Chen Xiangrong, Hou Jing, et al. Study of mechanical behavior of deep-buried marble at Jinping II hydropower station[J]. Chinese Journal of Rock Mechanics and Engineering, 2010, 29(10): 1999-2009.
[3] 李新平, 肖桃李, 汪斌, 等. 锦屏二级水电站大理岩不同应力路径下加 卸载试验研究[J]. 岩石力学与工程学报, 2012, 31(5): 882-889. Li Xinping, Xiao Taoli, Wang Bin, et al. Experimental study of Jinping II hydropower station marble under loading and unloading stress paths[J]. Chinese Journal of Rock Mechanics and Engineering, 2012, 31(5): 882-889.
[4] 刘立鹏, 汪小刚, 贾志欣, 等. 锦屏二级水电站大理岩复杂加卸载应力 路径力学特性研究[J]. 岩土力学, 2013, 34(8): 2287-2294. Liu Lipeng, Wang Xiaogang, Jia Zhixin. Experiment study of marble mechanical properties of Jinping II hydropower station under complex loading and unloading conditions [J]. Rock and Soil Mechanics, 2013,34 (8): 2287-2294.
[5] 孙卓恒, 侯哲生, 张爱萍. 锦屏二级水电站大理岩拉张型板裂化破坏 研究[J]. 水利与建筑工程学报, 2012, 10(2): 24-27. Sun Zhuoheng, Hou Zhesheng, Zhang Aiping. Research on tensile slabbing failure of marble at Jinping II hydropower station[J]. Journal of Water Resources and Architectural Engineering, 2012, 10(2): 24-27.
[6] 何满潮, 赵菲, 杜帅,等. 不同卸载速率下岩爆破坏特征试验分析[J]. 岩土力学, 2014, 35(10): 2737-2747. He Manchao, Zhao Fei, Du Shuai, et al. Rockburst characteristics based on experimental tests under different unloading rates [J]. Rock and Soil Mechanics, 2014, 35(10): 2737-2747.
[7] 邱士利, 冯夏庭, 张传庆, 等. 不同卸围压速率下深埋大理岩卸荷力学 特性试验研究[J]. 岩石力学与工程学报, 2010, 29(9): 1807-1817. Qiu Shili, Feng Xiating, Zhang Chuanqing, et al. Experimental research on mechanical properties of deep-buried marble under different unloading rates of confining pressures[J]. Chinese Journal of Rock Mechanics and Engineering, 2010, 29(9): 1807-1817.
[8] Wu F, Liu T, Liu J, et al. Excavation unloading destruction phenomena in rock dam foundations[J]. Bulletin of Engineering Geology and the Environment, 2009, 68(2): 257-262.
[9] 吕颖慧, 刘泉声, 胡云华. 基于花岗岩卸荷试验的损伤变形特征及其 强度准则[J]. 岩石力学与工程学报, 2009, 28(10): 2096-2103. Lü Yinghui, Liu Quansheng, Hu Yunhua. Damage deformation characteristics and its strength criterion based on unloading experiments of granites[J]. Chinese Journal of Rock Mechanics and Engineering, 2009, 28(10): 2096-2103.
[10] 张黎明, 王在泉, 石磊. 硬质岩石卸荷破坏特性试验研究[J]. 岩石力 学与工程学报, 2011, 30(10): 2012-2018. Zhang Liming, Wang Zaiquan, Shi Lei. Experimental study of hard rock failure characteristic under unloading condition[J]. Chinese Journal of Rock Mechanics and Engineering, 2011, 30(10): 2012-2018.
[11] Al-Ajmi A M, Zimmerman R W. Relation between the Mogi and the Coulomb failure criteria[J]. International Journal of Rock Mechanics and Mining Sciences, 2005, 42(3): 431-439.
[12] Al-Ajmi A M, Zimmerman R W. Stability analysis of vertical boreholes using the Mogi-Coulomb failure criterion[J]. International Journal of Rock Mechanics and Mining Sciences, 2006, 43(8): 1200-1211.
[13] Jimenez R, Ma X. A note on the strength symmetry imposed by Mogi's true-triaxial criterion[J]. International Journal of Rock Mechanics and Mining Sciences, 2013, 64(Complete): 17-21.
[14] 尤明庆. 统一强度理论应用于岩石的讨论[J]. 岩石力学与工程学报, 2013, 32(2): 258-265. You Mingqing. Discussion on the unified strength theories for rocks[J]. Chinese Journal of Rock Mechanics and Engineering 2013, 32(2): 258-265.
[15] 尤明庆. 统一强度理论的试验数据拟合及评价[J]. 岩石力学与工程 学报, 2008, 27(11): 2193-2204. You Mingqing. Fitting and evaluation of test data using unified strength theory[J]. Chinese Journal of Rock Mechanics and Engineering, 2008, 27(11): 2193-2204.
[16] Mogi K. Experimental rock mechanics[M]. London: CRC Press, 2007.
[17] 石磊. 不同加卸荷条件下大理岩力学及声发射特性试验及理论研究[D]. 青岛: 青岛理工大学, 2011. Shi Lei. Experimental and theoretical research of mechanical and acoustic emission characteristics of marble under different loading and unloading conditions[D]. Qingdao: Qingdao Technological University, 2011.
[18] 刘豆豆. 高地应力下岩石卸载破坏机理及其应用研究[D]. 济南: 山 东大学, 2008. Liu Doudou. Research on unloading failure mechanism of rock under high stress and its application[D]. Jinan: Shandong University, 2008.
[19] 何满潮, 苗金丽, 李德建, 等. 深部花岗岩试样岩爆过程实验研究[J]. 岩石力学与工程学报, 2007, 26(5): 865-876. He Manchao, Miao Jinli, Li Dejian, et al. Experimental study on rockburst processes of granite specimen at great depth[J]. Chinese Journal of Rock Mechanics and Engineering, 2007, 26(5): 865-876.
[20] 向天兵, 冯夏庭, 陈炳瑞, 等. 开挖与支护应力路径下硬岩破坏过程 的真三轴与声发射试验研究[J]. 岩土力学, 2008, 27(增1): 500-507. Xiang Tianbing, Feng Xiating, Chen Bingrui, et al. True triaxial and acoustic emission experimental study of failure process of hard rock under excavating and supporting stress paths[J]. Rock and Soil Mechanics, 2008, 27(Suppl 1): 500-507.
[21] 杜坤. 真三轴卸载下深部岩体破裂特性及诱发型岩爆机理研究[D]. 长沙: 中南大学, 2013. Du Kun. Study on the failure characteristics of deep rock and the mechanism of strainburst under true triaxial unloading condition[D]. Changsha: Central South University, 2013.
[22] 陈景涛. 高地应力下硬岩本构模型的研究和应用[D]. 北京: 中国科 学院研究生院, 2006. Chen Jingtao. Study on constitutive model for hard rock under high geostress condition and its applications in engineering[D]. Beijing: Chinese Academy of Sciences, 2006.
[23] 苗金丽. 岩爆的能量特征实验分析[D]. 北京: 中国矿业大学(北京), 2009. Miao Jinli. Experimental analysis on the energy characteristics of rockburst[D]. Beijing: China University of Mining and Technology (Beijing),2009.
[24] 周火明, 单治钢, 李维树, 等. 深埋隧洞大理岩卸载路径真三轴强度 参数研究[J]. 岩石力学与工程学报, 2012, 31(8): 1524-1529. Zhou Huoming, Shan Zhigang, Li Weishu, et al. Study of true triaxial strength parameters in unloading path of marbles in deep tunnel[J]. Chinese Journal of Rock Mechanics and Engineering, 2012, 31(8): 1524-1529.
[25] 李地元. 高应力硬岩脆性板裂破坏和应变型岩爆机理研究[D]. 长 沙: 中南大学, 2010. Li Diyuan. Study on the spalling failure of hard rock and the mechanism of strainburst under high in-situ stresses[D]. Changsha: Central South University, 2010.
