围压对节理岩体表征单元体尺寸的影响研究
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摘要
节理岩体的力学特性与其赋存的应力状态密切相关,已有的岩体表征单元体确定方法均没有考虑围压对表征单元体尺寸的影响。以某公路隧道为工程背景,采用三维离散元数值方法,对此问题进行研究。基于现场大量节理量测,统计出研究区岩体的优势节理组,建立岩体结构模型及三维离散元数值模型,模拟岩体的压缩试验,研究不同围压条件下表征单元体尺寸及岩体变形和力学特性的变化规律。结果表明:当围压小于20 MPa时,表征单元体尺寸随围压增加呈正相关增大;当围压大于20 MPa时,表征单元体尺寸不受围压影响,保持不变。当围压小于60 MPa时,岩体承载力随围压增加呈正相关增大;当围压大于60 MPa时,岩体承载力不随围压增加而变化。岩体的轴向应变、横向应变和体积应变随围压的变化规律也表现出明显的围压效应。
The mechanical properties of jointed rock mass are closely related to its occurrence of stress state.None of the existing methods in obtaining representative elementary volume has taken the effect of confining pressure on representative elementary volume(REV) size into account.Based on certain road tunnel project,this issue is studied with 3D discrete element method in this paper.The dominant joint sets of rock mass are calculated based on a large number of joint surveys in our study area.Then,the structure model and 3D discrete element model of rock mass are built,which are further employed to simulate the compression test of rock mass,thereby employing the effect of confining pressure on REV size,deformation and mechanical properties of rock mass.The results indicate but not limit to the following conclusions:when confining pressure is less than 20 MPa,REV size is positively correlated with the increase of confining pressure;when the confining pressure is greater than 20 MPa,REV size keep constant;when the confining pressure is less than 60 MPa,the capacity of rock mass is positively correlated with the increase of confining pressure;when the confining pressure is greater than 60 MPa,the rock mass capacity did not change as the confining pressure increasing.In addition,the axial strain,lateral strain and volumetric strain also showed significant effect of confining pressure.
The mechanical properties of jointed rock mass are closely related to its occurrence of stress state.None of the existing methods in obtaining representative elementary volume has taken the effect of confining pressure on representative elementary volume(REV) size into account.Based on certain road tunnel project,this issue is studied with 3D discrete element method in this paper.The dominant joint sets of rock mass are calculated based on a large number of joint surveys in our study area.Then,the structure model and 3D discrete element model of rock mass are built,which are further employed to simulate the compression test of rock mass,thereby employing the effect of confining pressure on REV size,deformation and mechanical properties of rock mass.The results indicate but not limit to the following conclusions:when confining pressure is less than 20 MPa,REV size is positively correlated with the increase of confining pressure;when the confining pressure is greater than 20 MPa,REV size keep constant;when the confining pressure is less than 60 MPa,the capacity of rock mass is positively correlated with the increase of confining pressure;when the confining pressure is greater than 60 MPa,the rock mass capacity did not change as the confining pressure increasing.In addition,the axial strain,lateral strain and volumetric strain also showed significant effect of confining pressure.
引文
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[11]WITHERSPOON P A,WANG J S Y,IWAI K,et al.Validity of cubic law for fluid flow in a deformable rock fracture[J].Water Resources Research,1980,16(6):1 016–1 024.
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[13]ODA M.Permeability tensor for discontinuous rock masses[J].Geotechnique,1985,35(4):483–495.
[14]中华人民共和国国家标准编写组.GB18306—2001中国地震动参数区划图[S].北京:中国标准出版社,2001.(The National Standards Compilation Group of People′s Republic of China.GB18306—2001 Seismic ground motion parameter zonation map of China[S].Beijing:Standards Press of China,2001.(in Chinese))
[2]王思敬.中国岩石力学与工程的世纪成就与历史使命[J].岩石力学与工程学报,2003,22(6):867–871.(WANG Sijing.Century achievements and new historical mission of rock mechanics and engineering in China[J].Chinese Journal of Rock Mechanics and Engineering,2003,22(6):867–871.(in Chinese))
[3]BEAR J.Dynamics of fluid in porous media[M].New York:American Elsevier,1972:19–21.
[4]孙广忠.岩体结构力学[M].北京:科学出版社,1988:23–61.(SUN Guangzhong.Mechanics of rock mass structure[M].Beijing:Science Press,1988:23–61.(in Chinese))
[5]周火明,盛谦,陈殊伟,等.层状复合岩体变形试验尺寸效应的数值模拟[J].岩石力学与工程学报,2004,23(2):289–292.(ZHOU Huoming,SHENG Qian,CHEN Shuwei,et al.Numerical simulation on size-effect in deformation test of layer composite rock mass[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(2):289–292.(in Chinese))
[6]刘顺桂,池永翔,王思敬,等.柱状节理玄武岩体抗剪强度参数尺寸效应研究[J].工程地质学报,2009,17(3):367–370.(LIU Shungui,CHI Yongxiang,WANG Sijing,et al.Size effect on shear strength of basalt rock mass with columnar joints[J].Journal of Engineering Geology,2009,17(3):367–370.(in Chinese))
[7]朱道建,杨林德,蔡永昌.柱状节理岩体各向异性特性及尺寸效应研究[J].岩石力学与工程学报,2009,28(7):1 405–1 414.(ZHU Daojian,YANG Linde,CAI Yongchang.Reaserch on anisotropic characteristics and size effect of columnar jointed rock mass[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(7):1405–1414.(in Chinese))
[8]周创兵,於三大.论岩体表征单元体积REV——岩体力学参数取值的一个基本问题[J].工程地质学报,1999,7(4):332–336.(ZHOU Chuangbing,YU Sanda.Representative elementary volume REV—a fundamental problem for selecting the mechanical parameters of jointed rock mass[J].Journal of Engineering Geology,1999,7(4):332–336.(in Chinese))
[9]周创兵,陈益峰,姜清辉.岩体表征单元体与岩体力学参数[J].岩土工程学报,2007,29(8):1 135–1 142.(ZHOU Chuangbing,CHEN Yifeng,JIANG Qinghui.Representative elementary volume and mechanical parameters of fractured rock masses[J].Chinese Journal of Geotechnical Engineering,2007,29(8):1 135–1 142.(in Chinese))
[10]向文飞,周创兵.裂隙岩体表征单元体研究进展[J].岩石力学与工程学报,2005,24(增2):5 686–5 692.(XIANG Wenfei,ZHOU Chuangbing.The advances in investigation of representative elementary volume for fractured rock mass[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(Supp.2):5 686–5 692.(in Chinese))
[11]WITHERSPOON P A,WANG J S Y,IWAI K,et al.Validity of cubic law for fluid flow in a deformable rock fracture[J].Water Resources Research,1980,16(6):1 016–1 024.
[12]LONG J C S,WITHERSPOON P A.The relationship of the degree of interconnection to permeability in fracture networks[J].Journal of Geophysical Research,1985,90(B4):3 087–3 098.
[13]ODA M.Permeability tensor for discontinuous rock masses[J].Geotechnique,1985,35(4):483–495.
[14]中华人民共和国国家标准编写组.GB18306—2001中国地震动参数区划图[S].北京:中国标准出版社,2001.(The National Standards Compilation Group of People′s Republic of China.GB18306—2001 Seismic ground motion parameter zonation map of China[S].Beijing:Standards Press of China,2001.(in Chinese))
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