非饱和重塑与结构性黄土等向压缩试验离散元分析
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摘要
为了研究非饱和重塑与结构性黄土在等向压缩条件下宏微观力学性质,进行了等向压缩室内试验的离散元数值分析。运用本团队提出的非饱和结构性黄土三维胶结接触模型,根据室内真三轴试验标定三维接触模型参数,进行了非饱和重塑与结构性黄土的等向压缩离散元模拟,并与室内试验结果进行了对比,在此基础上分析了其宏微观力学机理。结果表明:离散元模拟结果能较好的定性反映黄土的力学特征,非饱和黄土的孔隙比随平均应力先缓慢下降,后在屈服压力附近开始过渡到快速下降;胶结接触在达到某阈值平均应力时开始发生破坏;胶结开始发生大量破坏的阈值与压缩曲线上的结构屈服应力有很好的对应关系。
The macroscopic and microscopic mechanical responses of remolded and structured unsaturated loess are investigated under isotropic compression using the distinct element method(DEM). A three-dimensional(3D) cementation contact model developed for unsaturated structural loess is employed in the DEM with its parameters calibrated from the true triaxial tests on Chinese loess. After preparing the numerical unsaturated remolded and structured loess specimens, the isotropic compression tests are carried out. The DEM results show that the simulation can reproduce qualitatively the main mechanical behavior of the loess. The void ratio of unsaturated loess decreases slowly at first with the mean stress, and then begins to transit to a rapid reduction near the yield stress. When the mean stress of a certain threshold is reached, the cementing contact begins to break. There is a well correspondence between the threshold that a lot of contacts break down and the yield stress of the structure on the compression curve.
The macroscopic and microscopic mechanical responses of remolded and structured unsaturated loess are investigated under isotropic compression using the distinct element method(DEM). A three-dimensional(3D) cementation contact model developed for unsaturated structural loess is employed in the DEM with its parameters calibrated from the true triaxial tests on Chinese loess. After preparing the numerical unsaturated remolded and structured loess specimens, the isotropic compression tests are carried out. The DEM results show that the simulation can reproduce qualitatively the main mechanical behavior of the loess. The void ratio of unsaturated loess decreases slowly at first with the mean stress, and then begins to transit to a rapid reduction near the yield stress. When the mean stress of a certain threshold is reached, the cementing contact begins to break. There is a well correspondence between the threshold that a lot of contacts break down and the yield stress of the structure on the compression curve.
引文
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[4]李涛.非饱和结构性黄土三维离散元模拟与本构模型研究[D].上海:同济大学,2017.(LI Tao.Three-dimensional DEM simulation and constitutive model of unsaturated structural loess[D].Shanghai:Tongji University,2017.(in Chinese))
[5]李涛,蒋明镜,张鹏等.非饱和结构性黄土侧限压缩和湿陷试验三维离散元分析[J].岩土工程学报,2018,40(增刊1):39-44.(LI Tao,JIANG Ming-jing,ZHANG Peng.DEM analyses of oedo-meter and wetting tests on the unsaturated structured loess[J].Chinese Journal of Geotechnical Engineering,2018,40(S1):39-44.(in Chinese))
[6]JIANG M J,KONRAD J M,LEROUOEIL S.An efficient technique for generating homogeneous specimens for DEMstudies[J].Computers and Geotechnics,2003,30(7):579-597.
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[2]CUNDALL P A,STRACK O D L.A discrete numerical model for granular assemblies[J].Géotechnique,1979,29(1):47-65.
[3]JIANG M J,LI T,HU H J,et al.DEM analyses of one-dimensional compression and collapse behaviour of unsaturated structural loess[J].Computers and Geotechnics,2014,60:47-60.
[4]李涛.非饱和结构性黄土三维离散元模拟与本构模型研究[D].上海:同济大学,2017.(LI Tao.Three-dimensional DEM simulation and constitutive model of unsaturated structural loess[D].Shanghai:Tongji University,2017.(in Chinese))
[5]李涛,蒋明镜,张鹏等.非饱和结构性黄土侧限压缩和湿陷试验三维离散元分析[J].岩土工程学报,2018,40(增刊1):39-44.(LI Tao,JIANG Ming-jing,ZHANG Peng.DEM analyses of oedo-meter and wetting tests on the unsaturated structured loess[J].Chinese Journal of Geotechnical Engineering,2018,40(S1):39-44.(in Chinese))
[6]JIANG M J,KONRAD J M,LEROUOEIL S.An efficient technique for generating homogeneous specimens for DEMstudies[J].Computers and Geotechnics,2003,30(7):579-597.
[7]THORNTON C.Numerical simulations of deviatoric shear deformation of granular media[J].Géotechnique,2000,50(1):43-53.
[8]SATAKE M,Fabric tensor in granular materials[C]//Proceedings of IUTAM Symposium on Deformation and Failure of Granular Materials.Delft:Rotterdam,1982:63-68.
[9]BARRETO D,O’SULLIVAN C,ZDRAVKOVIC L.Quantifying the evolution of soil fabric under different stress paths[C]//Powders and Grains 2009:Proceedings of the 6th International Conference on Micromechanics of Granular Media.Golden,2009:181-184.