煤岩两体模型变形破坏数值模拟
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摘要
采用拉格朗日元法,在弹性岩石与弹性-应变软化煤体所构成的平面应变两体模型的上、下端面上不存在水平方向摩擦力条件下,模拟了模型的破坏过程、岩石高度对模型及煤体全程应力-应变曲线、煤体变形速率、煤体破坏模式及剪切应变增量分布的影响。结果表明,当模型的全程应力-应变曲线达到峰值时煤体内部的剪切带图案已经十分明显,在模型的应变硬化阶段,煤体中的应变局部化可视为模型失稳破坏的前兆,随岩石高度的增加,模型应力-应变曲线的软化段变得陡峭,这与单轴压缩条件下的解析解在定性上是一致的;煤体应力-应变曲线的软化段变得平缓,煤体消耗能量的能力增强;弹性阶段煤体的变形速率降低;煤体内部的剪切应变增量增加。煤体应力-应变曲线的软化段的斜率、弹性阶段煤体的变形速率、煤体内部的剪切应变增量及塑性耗散能都受岩石高度的影响,说明了岩石几何尺寸对煤体的影响(煤岩相互作用)是不容忽视的。
The failure process of plane strain two bodies model composed of rock specimen that is always elastic and coal specimen that is elastic prior to the peak stress and strain-softening beyond the peak and the effect of height of rock specimen on the complete stress-strain curves of model and coal specimen,the deformation rate and failure mode of coal specimen as well as the shear strain increment within coal specimen were numerically modeled by FLAC under the condition of smooth ends(no end-restraint effect).Numerical results show that when the peak stress of complete stress-strain curve of model is reached,the pattern of shear bands within coal specimen is very apparent.In strain-hardening stage of model,strain localization of coal specimen can be seen as a precursor to the unstable failure of model.Longer rock specimen leads to(1) steeper strain-softening branch of stress-strain curve of model,as is in qualitative agreement with the previous analytical solution that longer specimen results in steeper post-peak stress-strain in uniaxial compression;(2) more ductile strain-softening branch of stress-strain curves of coal specimen and higher plastic dissipated energy consumed by coal specimen;(3) lower deformation rate of coal specimen in stage elastic;and(4) higher shear strain increment within coal specimen.The slope of complete stress-strain curve beyond the peak stress of coal specimen,the deformation rate of coal specimen in stage elastic,the shear strain increment within coal specimen and the plastic dissipated energy consumed by coal specimen are influenced by the height of rock specimen,which reflects that the effect of geometrical size of rock specimen on the deformation and failure of coal specimen and the interaction between coal and rock specimens cannot be neglected.
The failure process of plane strain two bodies model composed of rock specimen that is always elastic and coal specimen that is elastic prior to the peak stress and strain-softening beyond the peak and the effect of height of rock specimen on the complete stress-strain curves of model and coal specimen,the deformation rate and failure mode of coal specimen as well as the shear strain increment within coal specimen were numerically modeled by FLAC under the condition of smooth ends(no end-restraint effect).Numerical results show that when the peak stress of complete stress-strain curve of model is reached,the pattern of shear bands within coal specimen is very apparent.In strain-hardening stage of model,strain localization of coal specimen can be seen as a precursor to the unstable failure of model.Longer rock specimen leads to(1) steeper strain-softening branch of stress-strain curve of model,as is in qualitative agreement with the previous analytical solution that longer specimen results in steeper post-peak stress-strain in uniaxial compression;(2) more ductile strain-softening branch of stress-strain curves of coal specimen and higher plastic dissipated energy consumed by coal specimen;(3) lower deformation rate of coal specimen in stage elastic;and(4) higher shear strain increment within coal specimen.The slope of complete stress-strain curve beyond the peak stress of coal specimen,the deformation rate of coal specimen in stage elastic,the shear strain increment within coal specimen and the plastic dissipated energy consumed by coal specimen are influenced by the height of rock specimen,which reflects that the effect of geometrical size of rock specimen on the deformation and failure of coal specimen and the interaction between coal and rock specimens cannot be neglected.
引文
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[2]林鹏,唐春安,陈忠辉,等.二岩体系统破坏全过程的数值模拟和实验研究[J].地震,1999,19(4):413-418.LIN Peng,TANG Chun-an,CHEN Zhong-hui,et al.Numerical and experimental study of deformation and failure behavior in a double rock specimen system[J].Earthquake,1999,19(4):413-418.
[3]陈忠辉,傅宇方,唐春安.单轴压缩下双试样相互作用的实验研究[J].东北大学学报(自然科学版),1997,18(4):382-385.CHEN Zhong-hui,FU Yu-fang,TANG Chun-an.Experimental study of interaction of two rock specimen under uniaxial compression[J].Journal of Northeastern University(Natural Science),1997,18(4):382-385.
[4]潘岳,王志强.狭窄煤柱冲击地压的折迭突变模型[J].岩土力学,2004,25(1):23-30.PAN Yue,WANG Zhi-qiang.Fold catastrophic model of rockburst in narrow coal pillar[J].Rock and Soil Mechanics,2004,25(1):23-30.
[5]李长洪,蔡美峰,乔兰,等.岩石全应力-应变曲线与岩爆的关系[J].北京科技大学学报,1999,21(6):513-515.LI Chang-hong,CAI Mei-feng,QIAO Lan,et al.Rock complete stress-strain and its relationship to rock burst[J].Journal of University of Science and Technology Beijing,1999,21(6):513-515.
[6]Brady B H G,Brown E T.Rock Mechanics for Underground Mining[M].UK:George Allen&Unwin,1985.
[7]WANG Xue-bin.Analysis of progressive failure of pillar and instability criterion based on gradient-dependent plasticity[J].Journal of Central South University of Technology(English Edition),2004,11(4):445-450.
[8]王淑坤,张万斌.复合模型力学性质试验研究[J].矿山压力与顶板管理,1994,(1):51-54.WANG Shu-kun,ZHANG Wan-bin.Experimental study on mechanical properties of compound model[J].Ground Pressure and Strata Control,1994,(1):51-54.
[9]齐庆新.层状煤岩体结构破坏的冲击矿压理论与实验研究[D].北京:煤炭科学研究总院北京开采研究所,1996.
[10]刘波,杨仁树,郭东明,等.孙村煤矿-1 100 m水平深部煤岩冲击倾向性组合试验研究[J].岩石力学与工程学报,2004,23(14):2 402-2 408.LIU Bo,YANG Ren-shu,GUO Dong-ming,et al.Burst-prone experiments of coal-rock combination-1100m level in Suncun coal mine[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(14):2 402-2 408.
[11]王学滨,潘一山,丁秀丽,等.平面应变状态下岩石剪切带网络数值模拟研究[J].岩土力学,2002,23(6):717-720.WANG Xue-bin,PAN Yi-shan,DING Xiu-li,et al.Simulation of multiple shear bands in strain softening rock in plane strain[J].Rock and Soil Mechanics,2002,23(6):717-720.
[12]王学滨,潘一山,盛谦,等.岩体假三轴压缩及变形局部化剪切带数值模拟[J].岩土力学,2001,22(3):323-326.WANG Xue-bin,PAN Yi-shan,SHENG Qian,et al.Simulation of triaxial compression and localization of deformation[J].Rock and Soil Mechanics,2001,22(3):323-326.
[13]WANG Xue-bin,PAN Yi-shan.Effect of relative stress on post-peak uniaxial compression fracture energy of concrete[J].Journal of Wuhan University of Technology-Materials Science Edition,2003,18(4):89-92.
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