法向卸荷条件下含单裂隙砂岩剪切强度与破坏特征试验研究
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摘要
在地下工程及边坡开挖和河谷下切等人为和自然因素作用下,岩体应力将沿至少某一个方向卸荷,造成复杂的岩体应力重新分布。这种卸荷易诱发岩体工程灾变,其中法向应力卸荷诱发岩体剪切破坏尤为突出。采用法向应力逐渐卸荷而剪切应力保持恒定的直剪试验方法,模拟开挖卸荷诱发岩体剪切破坏的力学机制。研究法向应力卸荷条件下,裂隙与剪切方向的夹角(后面简称夹角)及应力水平对单裂隙砂岩试样剪切变形、强度及破裂演化的影响规律。随着夹角从0°向180°增加,破坏模式依次表现为剪切破坏、张拉破坏、张剪混合破坏及剪切破坏的过渡。卸荷过程中法向位移和剪切位移均随初始法向应力的增大逐渐增大,而随初始剪应力的增大均逐渐减小。卸荷过程中法向位移随夹角的增大呈现先减小后增大的变化,而剪切位移对夹角不敏感。破坏时法向应力卸荷量随初始法向应力的增大逐渐增大,随初始剪应力的增大逐渐减小,随夹角的增大先减小后增大,夹角为60°时试样最容易发生破坏。通过对破裂面的应力状态分析,从力学机制的角度解释了破坏模式与夹角的相关性。研究成果丰富了卸荷岩体力学基础理论,为岩体工程开挖灾害防治提供理论支撑。
Under the influence of anthropogenic and natural factors such as underground engineering,slope excavation and valley cutting,the rock mass stress will release at least in one direction,which induces complex stress redistribution of rock mass. Such unloading easily induces rock mass engineering disasters,and the shear failure due to normal stress unloading is particularly prominent. The direct shear test with gradually unloading the normal stress but keeping the shear stress constant was performed to simulate the shear mechanical behavior of rock mass induced by excavating and unloading. The influences of the angle between the flaw and the shear direction and the stress level on deformation,strength and fracture evolution of single flaw sandstone under unloading normal stress were studied. It is revealed that,with increasing the angle from 0°to 180°,single flaw sandstone in sequence shows shear failure,tension failure,mixed tension-shear failure and shear failure. In the process of unloading,the normal and shear displacements increase with increasing the initial normal stress but decrease with rising the initial shear stress. The unloading normal displacement decreases firstly and then increases with increasing the angle,while the unloading shear displacement is not sensitive to the angle. The unloading amount at failure respectively increases,decreases,and decreases firstly and then increases with increasing the initial normal stress,the initial shear stress and the angle. The specimen is most prone to unloading shear failure when the angle is 60°. The correlation between the failure mode and the angle was presented based on the analysis of the stress state of the crack surface. The research results enrich the basic theory of unloading rock mass mechanics and have reference value for the prevention and treatment of excavation disasters in rock mass engineering.
Under the influence of anthropogenic and natural factors such as underground engineering,slope excavation and valley cutting,the rock mass stress will release at least in one direction,which induces complex stress redistribution of rock mass. Such unloading easily induces rock mass engineering disasters,and the shear failure due to normal stress unloading is particularly prominent. The direct shear test with gradually unloading the normal stress but keeping the shear stress constant was performed to simulate the shear mechanical behavior of rock mass induced by excavating and unloading. The influences of the angle between the flaw and the shear direction and the stress level on deformation,strength and fracture evolution of single flaw sandstone under unloading normal stress were studied. It is revealed that,with increasing the angle from 0°to 180°,single flaw sandstone in sequence shows shear failure,tension failure,mixed tension-shear failure and shear failure. In the process of unloading,the normal and shear displacements increase with increasing the initial normal stress but decrease with rising the initial shear stress. The unloading normal displacement decreases firstly and then increases with increasing the angle,while the unloading shear displacement is not sensitive to the angle. The unloading amount at failure respectively increases,decreases,and decreases firstly and then increases with increasing the initial normal stress,the initial shear stress and the angle. The specimen is most prone to unloading shear failure when the angle is 60°. The correlation between the failure mode and the angle was presented based on the analysis of the stress state of the crack surface. The research results enrich the basic theory of unloading rock mass mechanics and have reference value for the prevention and treatment of excavation disasters in rock mass engineering.
引文
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[18]陈卫忠,李术才,邱祥波,等.岩石裂纹扩展的实验与数值分析研究[J].岩石力学与工程学报,2003,22(1):18-23.(CHENWeizhong,LI Shucai,QIU Xiangbo,et al.Experimental and numerical research on crack propagation in rock under compression[J].Chinese Journal of Rock Mechanics and Engineering,2003,22(1):18-23.(in Chinese))
[19]朱维申,陈卫忠,申晋.雁形裂隙扩展的模型试验及断裂力学机制研究[J].固体力学学报,1998,19(4):355-360.(ZHU Weishen,CHEN Weizhong,SHEN Jin.Simulation experiment and fracture mechanism-study on propagation of echelon pattern cracks[J].Acta Mechanics Solida Sinica,1998,19(4):355-360.(in Chinese))
[20]黄达,黄润秋.卸荷条件下裂隙岩体变形破坏及裂纹扩展演化的物理模型试验[J].岩石力学与工程学报,2010,29(3):502-512.(HUANG Da,HUANG Runqiu.Physical model test on deformation failure and crack propagation evolvement of fissured rocks under unloading[J].Chinese Journal of Rock Mechanics and Engineering,2010,29(3):502-512.(in Chinese))
[21]李建林,孟庆义.卸荷岩体的各向异性研究[J].岩石力学与工程学报,2001,20(3):338-341.(LI Jianlin,MENG Qingyi.Anisotropic study of unloaded rock mass[J].Chinese Journal of Rock Mechanics and Engineering,2001,20(3):338-341.(in Chinese))
[22]中华人民共和国行业标准编写组.SL 264-2001水利水电工程岩石试验规程[S].北京:中国水利水电出版社,2001.(The Professional Standards Compilation Group of People?s Republic of China.SL 264-2001 Specifications for rock tests in water conservancy and hydroelectric engineering[S].Beijing:China Water Power Press,2001.(in Chinese))
[23]ZHU T T,HUANG D.Experimental investigation of the shear mechanical behavior of sandstone under unloading normal stress[J].International Journal of Rock Mechanics and Mining Sciences,2019,114(1):186-194.
[2]黄达,黄润秋,王家祥.开挖卸荷条件下大型地下硐室块体稳定性的对比分析[J].岩石力学与工程学报,2007,26(增2):4 115-4 122.(HUANG Da,HUANG Runqiu,WANG Jiaxiang.Contrastive analysis of stability of block in large underground caverns under conditions of excavation and unloading[J].Chinese Journal of Rock Mechanics and Engineering,2007,26(Supp.2):4 115-4 122.(in Chinese))
[3]沈明荣,陈建峰.岩体力学[M].上海:同济大学出版社,2006:12-21.(SHEN Mingrong,CHEN Jianfeng.Rock mass mechanics[M].Shanghai:Tongji University Press,2006:12-21.(in Chinese))
[4]刘红岩,黄妤诗,李楷兵,等.预制节理岩体试件强度及破坏模式的试验研究[J].岩土力学,2013,34(5):1 235-1 241.(LIUHongyan,HUANG Yushi,LI Kaibing,et al.Test study of strength and failure mode of pre-existing jointed rock mass[J].Rock and Soil Mechanics,2013,34(5):1 235-1 241.(in Chinese))
[5]LAJAI E Z.Shear strength of weakness planes in rock[J].International Journal of Rock Mechanics and Mining Sciences,1969,6(7):499-515.
[6]SAVILAHTI T,NORDLUND E,STEPHANSSON O.Shear box testing and modeling of joint bridges[C]//Proceedings of the International Symposium on Rock Joints.[S.l.]:[s.n.],1990:295-300.
[7]GEHLE C,KUTTER H K.Breakage and shear behavior of intermittent rock joints[J].International Journal of Rock Mechanics and Mining Sciences,2003,40(5):687-700.
[8]WONGR H C,CHAUK T,TANG C A,et.a1.Analysis of crack coalescence in rock-like materials containing three flaws-part I:experimental approach[J].International Journal of Rock Mechanics and Mining Sciences,2001,38(7):909-924.
[9]WONG R H C,CHAU K T.Crack coalescence in a rock-like materiel containing two cracks[J].International Journal of Rock Mechanics and Mining Sciences,1998,35(2):147-164.
[10]WONG R H C,HUANG M L,JIAO M R,et al.The mechanisms of crack propagation from surface 3D fracture under uniaxial compression[J].Key Engineering Materials,2004,261-263:219-224.
[11]WONG R H C,LAW C M,CHAU K T,et al.Crack propagation from3D surface fractures in PMMA and marble specimens under uniaxial compression[J].International Journal of Rock Mechanics and Mining Sciences,2004,41(3):360-366.
[12]WONG R H C,GUO Y S,LI L Y,et al.Anti-wing crack study from3D surface flaw in real rock[C]//The 6th European Conference on Fracture.Alexandroupolis:[s.n.],2006:1-8.
[13]WONG L N Y,EINSTEIN H H.Crack coalescence in molded gypsum and carrara marble:part 1.macroscopic observations and interpretation[J].Rock Mechanics and Rock Engineering,2009,42(3):475-511.
[14]刘东燕,朱可善.含断续节理岩体强度的各向异性研究[J].岩石力学与工程学报,1998,17(4):366-371.(LIU Dongyan,ZHU Keshan.A study of strength anisotropy of rock mass containing intermittent joints[J].Chinese Journal of Rock Mechanics and Engineering,1998,17(4):366-371.(in Chinese))
[15]王瑞红,李建林,蒋昱州,等.含预制节理岩体卸荷条件下力学特性试验研究[J].岩土力学,2012,33(11):3 257-3 262.(WANGRuihong,LI Jianlin,JIANG Yuzhou,et al.Experimental research on mechanical property of rock mass with prefabricated joints under unloading condition[J].Rock and Soil Mechanics,2012,33(11):3 257-3 262.(in Chinese))
[16]刘远明.基于直剪试验的非贯通节理岩体扩展贯通研究[博士学位论文][D].上海:同济大学,2007.(LIU Yuanming.Study of failure models and strength of rock mass containing discontinuous joints in direct shear test[Ph.D.Thesis][D].Shanghai:Tongji University,2007.(in Chinese))
[17]刘远明,夏才初.非贯通节理岩体直剪贯通模型和强度研究[J].岩土工程学报,2006,28(10):l 242-1 247.(LIU Yuanming,XIA Caichu.Study of models and strength behavior of rock mass containing discontinuous joints in direct shear[J].Chinese Journal of Geotechnical Engineering,2006,28(10):l 242-l 247.(in Chinese))
[18]陈卫忠,李术才,邱祥波,等.岩石裂纹扩展的实验与数值分析研究[J].岩石力学与工程学报,2003,22(1):18-23.(CHENWeizhong,LI Shucai,QIU Xiangbo,et al.Experimental and numerical research on crack propagation in rock under compression[J].Chinese Journal of Rock Mechanics and Engineering,2003,22(1):18-23.(in Chinese))
[19]朱维申,陈卫忠,申晋.雁形裂隙扩展的模型试验及断裂力学机制研究[J].固体力学学报,1998,19(4):355-360.(ZHU Weishen,CHEN Weizhong,SHEN Jin.Simulation experiment and fracture mechanism-study on propagation of echelon pattern cracks[J].Acta Mechanics Solida Sinica,1998,19(4):355-360.(in Chinese))
[20]黄达,黄润秋.卸荷条件下裂隙岩体变形破坏及裂纹扩展演化的物理模型试验[J].岩石力学与工程学报,2010,29(3):502-512.(HUANG Da,HUANG Runqiu.Physical model test on deformation failure and crack propagation evolvement of fissured rocks under unloading[J].Chinese Journal of Rock Mechanics and Engineering,2010,29(3):502-512.(in Chinese))
[21]李建林,孟庆义.卸荷岩体的各向异性研究[J].岩石力学与工程学报,2001,20(3):338-341.(LI Jianlin,MENG Qingyi.Anisotropic study of unloaded rock mass[J].Chinese Journal of Rock Mechanics and Engineering,2001,20(3):338-341.(in Chinese))
[22]中华人民共和国行业标准编写组.SL 264-2001水利水电工程岩石试验规程[S].北京:中国水利水电出版社,2001.(The Professional Standards Compilation Group of People?s Republic of China.SL 264-2001 Specifications for rock tests in water conservancy and hydroelectric engineering[S].Beijing:China Water Power Press,2001.(in Chinese))
[23]ZHU T T,HUANG D.Experimental investigation of the shear mechanical behavior of sandstone under unloading normal stress[J].International Journal of Rock Mechanics and Mining Sciences,2019,114(1):186-194.
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