张杰, 李萍, 李同录, 等. 2021. 黄土沉积过程及微结构模型的非连续变形分析[J]. 工程地质学报, 29(4): 1199-1206. doi: 10.13544/j.cnki.jeg.2019-517.
    引用本文: 张杰, 李萍, 李同录, 等. 2021. 黄土沉积过程及微结构模型的非连续变形分析[J]. 工程地质学报, 29(4): 1199-1206. doi: 10.13544/j.cnki.jeg.2019-517.
    Zhang Jie, Li Ping, Li Tonglu, et al. 2021. Discontinuous deformation simulation of loess sedimentation process and microstructure model [J]. Journal of Engineering Geology, 29(4): 1199-1206. doi: 10.13544/j.cnki.jeg.2019-517.
    Citation: Zhang Jie, Li Ping, Li Tonglu, et al. 2021. Discontinuous deformation simulation of loess sedimentation process and microstructure model [J]. Journal of Engineering Geology, 29(4): 1199-1206. doi: 10.13544/j.cnki.jeg.2019-517.

    黄土沉积过程及微结构模型的非连续变形分析

    DISCONTINUOUS DEFORMATION SIMULATION OF LOESS SEDIMEN-TATION PROCESS AND MICROSTRUCTURE MODEL

    • 摘要: 黄土是一种具有特殊结构的多孔隙、弱胶结的松散沉积物,存在典型的微观架空结构,其力学行为是微观结构变形与破坏的宏观体现。从本质上揭示黄土的力学行为,需从黄土微结构出发,而黄土的物质组成和微结构特征受其特殊的风积成因所控制,基于此本文提出了一种模拟黄土沉积过程并构建其初始结构模型的方法。为了生成黄土沉积后所形成的微结构模型,并对其进行变形模拟,首先在确定黄土颗粒形态的基础上利用Monte Carlo法生成沉积前的黄土颗粒群,然后引入非连续变形分析方法(DDA)模拟颗粒的下落,该方法能够模拟颗粒下落过程中的相互碰撞及摩擦,由此建立与实际比较接近的黄土初始结构模型。从模型中可以识别出大、中、小3类孔隙结构和台阶(staircase)、重叠(stack)、点接触(point contact)、T型4种接触形式。对所生成的黄土结构模型进行不同压力下的压缩试验,选择不同部位的颗粒作出了径向分布函数,从微观角度说明了黄土在压缩过程中大孔隙和架空结构会首先被破坏。设计了与数值模拟相同条件下的物理模型试验,将两者试验结果进行对比,结果表明数值模拟与物理模型试验的e-lgp压缩曲线的趋势大致相同,表明所提出方法是可行的。该方法为进一步开展黄土力学行为的微观分析提供了基础。

       

      Abstract: Loess is a porous,weakly cemented loose sediments with typical open structure. The mechanical characteristics of loess are typically the macro reflection of its deformation and failure in microstructure. To reveal the mechanical behavior of loess,it is necessary to start from the microstructure of loess since the material composition and microstructure characteristics are controlled by its special aeolian genesis. Based on this,a method to simulate the process of loess deposition and construct its initial structure model is proposed. In order to generate the microstructure model formed by the loess deposition process and simulate the deformation,firstly,the particle group of loess before deposition is generated by Monte Carlo method on the basis of determining the morphology of loess particles. Then the discontinuous deformation analysis method(DDA) is adopted to establish the structure model of loess and to simulate the falling process of loess particles considering the collision force and friction force between particles. From the model,three pore types and four major contact structures can be identified. The consolidation test of the loess initial structure model under different pressures is carried out. The radial distribution function is obtained by selecting particles from different parts. It microscopically illustrates that the macropores and open structures of the loess can be destroyed first during the compression process. The numerical results are compared with the results of physical model test under the same conditions. The results show that the trend of the e-lgp compression curve of the numerical simulation and the physical model test is about the same,indicating that the proposed method is feasible. This method provides a basis for further microscopic analysis of loess mechanical behavior.

       

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