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| EXPERIMENTAL RESEARCH ON SANDSTONE PRE-PEAK UNLOADING PROCESS UNDER HIGH CONFINING PRESSURE |
| (State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China) |
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Abstract A series of pre-peak unloading tests on sandstone from Chongqing Yuzui under the range of initial confining pressure between 10 MPa and 130 MPa have been carried out，in order to analyze rock deformation behavior，failure deformation，peak strength and residual strength criterion，the evolvement property of dilatancy parameter during the process of unloading. The conventional triaxial compression tests of sandstone have been also performed. The results show that：(1) The triaxial compression tests performed under different confining pressures discover that the stress drop of the stress-strain curves does not appear when confining pressure reaches above the value of 130 MPa；so it can be considered as the transition point of brittleness and ductility. (2) Under conventional compression，the dilatancy amount at the pre-peak of deviatoric stress is smaller compared with post-peak；while under unloading stress path，the sample exhibits greater dilatancy amount at pre-peak of deviatoric stress. (3) Under the same initial stress，the variation in stress required for rock unloading failure is comparably less than that of triaxial compressive process，which reveals that unloading stress path make sandstone sample more prone to failure. (4) Under the same confining pressure，the rupture angle of unloading failure is greater than that of loading failure. (5) Shear strength parameters have been evaluated by Coulomb laws；it is found that the cohesion c decreases，but the inner friction angle increases during unloading；under the two loading stress paths，the cohesion c decreases greatly and the inner friction angle has a little change at the residual deformation stage. (6) The restriction on the behavior of dilatancy by confining pressure is significant，when the confining pressure is higher，the peak dilatancy angle would be smaller，the dilatancy angle increases quickly to the peak after the beginning of unloading；the peaks of deviatoric stress and the dilatancy angle exhibit a time asynchrony；moreover，the former lags behind the latter；the dilatancy angle under unloading stress path is greater than that under conventional loading stress path and needs smaller plastic shear strain to arrive at the peak dilatancy angle，which shows that the unloading stress path makes the dilatancy property more significant. These conclusions have revealed the unloading mechanical properties of sandstone under high geostress and provided reliable theoretical reference for the numerical simulation about excavation and design for the stability analysis of deep-buried access tunnel in West China.
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Received: 26 October 2010
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| [1] 尤明庆，华安增. 岩石试样的三轴卸围压试验[J]. 岩石力学与工程学报，1998，17(1)：24–29.(YOU Mingqing，HUA Anzeng. Triaxial confining depressure test of rock sample[J]. Chinese Journal of Rock Mechanics and Engineering，1998，17(1)：24–29.(in Chinese))
[2] 李建林. 卸荷岩体力学理论与应用[M]. 北京：中国建筑工业出版社，1999.(LI Jianlin. Theory and application of rock mass mechanics under unloading conditions[M]. Beijing：China Architecture and Building Press，1999.(in Chinese))
[3] 吕爱钟，焦春茂. 岩石力学中两个基本问题的探讨[J]. 岩石力学与工程学报，2004，23(23)：4 095–4098.(LU Aizhong，JIAO Chunmao. Discussion of two elementary problems in rock mechanics[J]. Chinese Journal of Rock Mechanics and Engineering，2004，23(23)：4 095– 4 098.(in Chinese))
[4] 吕颖慧，刘泉声，江 浩. 基于高应力下花岗岩卸荷试验的力学变形特性研究[J]. 岩土力学，2010，31(2)：337–344.(LU Yinghui，LIU Quansheng，JIANG Hao. Study of mechanical deformation characteristics of granite in unloading experiments of high stress[J]. Rock and Soil Mechanics，2010，31(2)：337–344.(in Chinese))
[5] 周小平，哈秋聆，张永兴，等. 峰前围压卸荷条件下岩石的应力–应变全过程分析和变形局部化研究[J]. 岩石力学与工程学报，2005，24(18)：3 236–3 245.(ZHOU Xiaoping，HA Qiuling，ZHANG Yongxing，et al. Analysis of localization of deformation and complete stress-strain relation for mesoscopic heterogeneous brittle rock materials when axial stress is held constant while lateral confinement is reduced[J]. Chinese Journal of Rock Mechanics and Engineering，2005，24(18)：3 236–3 245.(in Chinese))
[6] 李天斌，王兰生. 卸荷应力状态下玄武岩变形破坏特征的试验研究[J]. 岩石力学与工程学报，1993，12(4)：321–327.(LI Tianbin，WANG Lansheng. An experimental study on the deformation and failure features of a basalt under unloading condition[J]. Chinese Journal of Rock Mechanics and Engineering，1993，12(4)：321–327.(in Chinese))
[7] 李宏哲，夏才初，闫子舰，等. 锦屏水电站大理岩在高应力条件下的卸荷力学特性研究[J]. 岩石力学与工程学报，2007，26(10)：2 104– 2 109.(LI Hongzhe，XIA Caichu，YAN Zijian，et al. Study on marble unloading mechanical properties of Jinping hydropower station under high geostress conditions[J]. Chinese Journal of Rock Mechanics and Engineering，2007，26(10)：2 104–2 109.(in Chinese))
[8] 黄润秋，黄 达. 高地应力条件下卸荷速率对锦屏大理岩力学特性影响规律试验研究[J]. 岩石力学与工程学报，2010，29(1)：21–33.(HUANG Runqiu，HUANG Da. Experimental research on affection laws of unloading rates on mechanical properties of Jinping marble under high geostress[J]. Chinese Journal of Rock Mechanics and Engineering，2010，29(1)：21–33.(in Chinese))
[9] 黄润秋，黄 达. 卸荷条件下花岗岩力学特性试验研究[J]. 岩石力学与工程学报，2008，27(11)：2 205–2 213.(HUANG Runqiu，HUANG Da. Experimental research on mechanical properties of granites under unloading condition[J]. Chinese Journal of Rock Mechanics and Engineering，2008，27(11)：2 205–2 213.(in Chinese))
[10] 汪 斌，朱杰兵，邬爱清，等. 锦屏大理岩加、卸载应力路径下力学性质试验研究[J]. 岩石力学与工程学报，2008，27(10)：2 138– 2 145.(WANG Bin，ZHU Jiebing，WU Aiqing，et al. Experimental study on mechanical properties of Jinping marble under loading and unloading stress paths[J]. Chinese Journal of Rock Mechanics and Engineering，2008，27(10)：2 138–2 145.(in Chinese))
[11] 何满潮，谢和平，彭苏萍，等. 深部开采岩体力学研究[J]. 岩石力学与工程学报，2005，24(16)：2 803–2 813.(HE Manchao，XIE Heping，PENG Suping，et al. Study on rock mechanics in deep mining engineering[J]. Chinese Journal of Rock Mechanics and Engineering，2005，24(16)：2 803–2 813.(in Chinese))
[12] 陈 勉. 中国深层岩石力学研究及在石油工程中的应用[J]. 岩石力学与工程学报，2004，23(14)：2 455–2 462.(CHEN Mian. Review of study on rock mechanics at great depth and its applications to petroleum engineering of China[J]. Chinese Journal of Rock Mechanics and Engineering，2004，23(14)：2 455–2 462.(in Chinese))
[13] 蔡美峰，何满潮，刘东燕. 岩石力学与工程[M]. 北京：科学出版社，2002.(CAI Meifeng，HE Manchao，LIU Dongyan. Rock mechanics and engineering[M]. Beijing：Science Press，2002.(in Chinese))
[14] 赵星光，蔡 明，蔡美峰. 岩石剪胀角模型与验证[J]. 岩石力学与工程学报，2010，29(5)：970–981.(ZHAO Xingguang，CAI Ming，CAI Meifeng. A rock dilation angle model and its verification[J]. Chinese Journal of Rock Mechanics and Engineering，2010，29(5)：970–981.(in Chinese))
[15] VERMEER P A，DE BORST R. Non-associated plasticity for soils，concrete and rock[J]. Heron，1984，29(3)：1–64. |
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2011, Vol. 30 
