含不同随机缺陷数目岩样的破坏过程、前兆及全部变形特征
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摘要
利用拉格朗日元法模拟了平面应变单轴压缩条件下具有初始随机材料缺陷的岩石试样的破坏过程、前兆和宏观力学响应.利用若干FISH函数于岩样内部规定初始缺陷并计算全部变形特征.比密实岩石弱的缺陷在破坏之后经历理想塑性行为密实岩石在破坏之后先是经历线性应变软化行为,然后是理想塑性行为.随着缺陷数目的增加,剪切带间距缩小;岩样的强度下降.在应变软化阶段,最大不平衡力的明显的突增是由于被剪切带切割的试样块体发生了沿剪切带方向的运动.试样内部的缺陷数目越少,应变软化阶段最大不平衡力的峰值越高.无论从单元破坏角度,还是从侧向应变-轴向应变曲线、体积应变-轴向应变曲线、计算得到的泊松比-轴向应变曲线角度,都得到了相同的结论(即,缺陷越多,破坏前兆越明显).采用两条倾斜的扫描线对岩样最终的破坏形态进行了扫描,发现当扫描线间距等于半个至1个单元长度时,初始随机缺陷位置与岩样最终破坏形态具有很好的相关性.
The failure processes, precursors to failure and macroscopically mechanical responses of heterogeneous rock specimens with initially random material imperfections in uniaxial plane strain compression are numerically modeled using FLAC.FISH functions are used to generate initial imperfections and to calculate overall deformational characteristics. Beyond the failure of the imperfection that is weaker than the intact rock element, it undergoes ideal plastic behavior, while the intact rock element exhibits linear strain-softening behavior and then ideal plastic behavior once failure occurs. With an increase of the number of imperfections, the shear band spacing decreases and the strength of the specimen decreases. In the strain-softening stage, the rapid increase in the maximum unbalanced force is due to the movement of rock blocks separated by shear bands. The lower the number of imperfections is, the higher the maximum unbalanced force in strain-softening stage is. Both the failure process of the rock specimen and the overall deformation (lateral strain-axial strain curve, volumetric strain-axial strain curves and calculated Poisson's ratio-axial strain curve) show that the precursors to failure become apparent as the number of imperfections increases. Using two scanning lines, the final failure pattern of a specimen is scanned. It is found that when the spacing of scanning lines is in the range of half and one element length, both the initial imperfection distribution and the final failure pattern have a good correlation.
The failure processes, precursors to failure and macroscopically mechanical responses of heterogeneous rock specimens with initially random material imperfections in uniaxial plane strain compression are numerically modeled using FLAC.FISH functions are used to generate initial imperfections and to calculate overall deformational characteristics. Beyond the failure of the imperfection that is weaker than the intact rock element, it undergoes ideal plastic behavior, while the intact rock element exhibits linear strain-softening behavior and then ideal plastic behavior once failure occurs. With an increase of the number of imperfections, the shear band spacing decreases and the strength of the specimen decreases. In the strain-softening stage, the rapid increase in the maximum unbalanced force is due to the movement of rock blocks separated by shear bands. The lower the number of imperfections is, the higher the maximum unbalanced force in strain-softening stage is. Both the failure process of the rock specimen and the overall deformation (lateral strain-axial strain curve, volumetric strain-axial strain curves and calculated Poisson's ratio-axial strain curve) show that the precursors to failure become apparent as the number of imperfections increases. Using two scanning lines, the final failure pattern of a specimen is scanned. It is found that when the spacing of scanning lines is in the range of half and one element length, both the initial imperfection distribution and the final failure pattern have a good correlation.
引文
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[20] Bardet J P. Orientation of shear bands in frictional soils[J]. Journal of Engineering Mechanics, ASCE, 1991, 117(7) :1466-1484．
[21] 王学滨,赵福成,潘一山.孔隙压力对含随机缺陷岩石破坏过程及全部变形特征的影响[J].防灾减灾工程学报,2009,29(1) :1-8． Wang X B, Zhao F C, Pan Y S. Effect of pore pressure on failure processes and overall deformational characteristics of rock specimen with random defects[J]. Journal of Disaster Prevention and Mitigation Engineering, 2009, 29(1) :1-8．
[2] 张楚汉.论岩石、混凝土离散接触断裂分析[J].岩石力学与工程学报,2008,27(2) :217-235． Zhang C H. Discrere-contact-fracture analysis of rock and concrete [J]. Chinese Journal of Rock Mechanics and Engineering, 2008, 27(2) :217-235．
[3] Scholz C H. Microfracturing and the inelastic deformation of rock in compression [J]. Journal of Geophysical Research, 1968, 73(4) : 1417-1432．
[4] 李世愚,腾春凯,卢振业,等.地震破裂的集结及其前兆意义[J].地震学报,2000,22(2) :201-209． Li S Y, Teng C K, Lu Z Y, et al. Nucleation of earthquake rupture and its significance as precursors [J]. Acta Seismologica Sinica, 2000, 22(2) :201-209．
[5] Hall S A, De Sanctis F, Viggiani G. Monitoring fracture propagation in a soft rock (Neapolitan tuff) using acoustic emissions and digital images [J]. Pure and Applied Geophysics, 2006, 163(10) :2171-2204．
[6] Kuksenko V, Tomilin N, Damaskinskaya E, et al. A two-stage model of fracture of rocks[J]. Pure and Applied Geophysics, 1996, 146(2) :253-263．
[7] Tang C A, Kou S Q. Crack propagation and coalescence in brittle materials under compression[J]. Engineering Fracture Mechanics, 1998, 61(3-4) :311-324．
[8] Fang Z, Harrison J P. Development of a local degradation approach to the modeling of brittle fracture in heterogeneous rocks[J]. International Journal of Rock Mechanics and Mining Sciences, 2002, 39(4) :443-457．
[9] 王学滨.软化模量对岩样全部变形特征的影响[J].岩土工程学报,2006,28(5) :600-605． Wang X B. Effect of softening modulus on entire deformational characteristics of rock specimen[J]. Chinese Journal of Geotechnical Engineering, 2006, 28(5) :600-605．
[10] 王学滨.泊松比对岩样破坏模式及全部变形特征的影响[J].地质力学学报,2007,13(3) :220-226． Wang X B. Effects of Poisson's ratio on failure mode and overall deformational characteristics of a rock specimen[J]. Journal of Geomechanics, 2007, 13(3) :220-226．
[11] 王学滨.材料缺陷对岩样变形局部化影响数值模拟[J].岩土力学,2006,27(8) :1241-1247． Wang X B. Numerical simulation of influence of material imperfection on strain localization [J]. Rock and Soil Mechanics, 2006, 27(8) : 1241-1247．
[12] 王学滨.扩容角对初始随机材料缺陷岩石试样破坏过程及力学行为的影响[J].中国有色金属学报,2007,17(7) :1063-1071． Wang X B. Effects of dilation angle on failure process and mechanical behavior for rock specimen with random material imperfections [J]. The Chinese Journal of Nonferrous Metals, 2007, 17(7) : 1063-1071．
[13] 王学滨,潘一山.加载速度对随机缺陷岩样破坏过程的影响[J].岩石力学与工程学报,2007,26(增1) :3493-3497． Wang X B, Pan Y S. Influence of loading velocity on failure process of rock specimen with initially random material imperfections[J]. Chinese Journal of Rock Mechanics and Engineering, 2007, 26(Suppl.1) :3493-3497．
[14] Wang X B. Failure process and stress-strain curve of plane strain rock specimen with initially random material imperfections[J]. Key Engineering Materials, 2007, 353-358:1133-1136．
[15] 王学滨.平面应变双轴压缩岩样剪应力异常及破坏过程模拟[J].地球物理学进展,2008,23(5) :1417-1424． Wang X B. Numerical simulation for anomalies of shear stress and failure process of rock under biaxial plane strain compression[J]. Progress in Geophysics, 2008, 23(5) : 1417-1424．
[16] Hu N, Molinari J F. Shear bands in dense metallic granular materials[J]. Journal of the Mechanics and Physics of Solids, 2004, 52(3) :499-531．
[17] 王学滨,马剑,刘杰,等.基于梯度塑性本构理论的岩样侧向变形分析(Ⅰ):基本理论及本构参数对侧向变形的影响[J].岩土力学,2004,25(6) :904-908． Wang X B, et al. Analysis of lateral deformation of rock specimen based on gradient-dependent plasticity (Ⅰ): basic-theory and effect of constitutive parameters on lateral deformation[J]. Rock and Soil Mechanics, 2004, 25(6) : 904-908．
[18] Vermeer P A. The orientation of shear bands in biaxialtests [J]. Geotechnique, 1990, 40(2) :223-236．
[19] Vardoulakis I. Shear band inclination and shear modulus of sand in biaxial tests[J]. International Journal for Numerical and Analytical Methods in Geomechanics, 1980, 4(2) :103-119．
[20] Bardet J P. Orientation of shear bands in frictional soils[J]. Journal of Engineering Mechanics, ASCE, 1991, 117(7) :1466-1484．
[21] 王学滨,赵福成,潘一山.孔隙压力对含随机缺陷岩石破坏过程及全部变形特征的影响[J].防灾减灾工程学报,2009,29(1) :1-8． Wang X B, Zhao F C, Pan Y S. Effect of pore pressure on failure processes and overall deformational characteristics of rock specimen with random defects[J]. Journal of Disaster Prevention and Mitigation Engineering, 2009, 29(1) :1-8．
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