DEM analysis of evolution law of bond degradation for structured soils
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摘要: 结构性土体通常指粒间含有胶结的土体,可看成一种特殊的胶结颗粒材料,探明结构性土体的胶结破损演化规律是加深结构性土体宏微观力学性质认识及建立结构性土本构模型的关键。由于试验手段难以定量获取胶结破损信息,通过离散单元法分析了结构性土体的胶结破损演化规律。首先采用相对完备的胶结接触模型建立了结构性土体离散元试样,接触模型考虑了颗粒及胶结物质的抗转动和抗扭转作用以及胶结尺寸对刚度和强度的影响；然后开展了结构性土侧限压缩、等向压缩、等应力比压缩以及常规三轴和真三轴试验的离散元数值分析,再现了结构性土的主要宏观力学特征；在此基础上的胶结破损演化分析表明胶结破损参量B0演化具有明显的应力路径相关性,而新提出的破损参量Bσ应力路径相关性低,通过Bσ与等效塑性应变的指数函数关系,可以描述结构性土体的胶结破损演化情况。
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关键词:
- 结构性土 /
- 胶结颗粒材料（理想结构性土） /
- 离散单元法 /
- 胶结破损演化 /
- 本构模型
Abstract: The evolution of bond degradation is essential for analyzing the macro-and micro-scopic behaviors and establishing constitutive models for structured soils with cementation bond which is a kind of bonded granular material. The discrete element method is employed to analyze the evolution of bond degradation on account of the disadvantage of laboratory tests in bond breakage quantitative analysis. First, the discrete numerical sample is generated by installing a relatively completed bond contact model incorporating the interparticle rolling and twisting resistances and the influences of bond size on the contact stiffness and strength. The DEM simulation reproduces the key mechanical behaviors of one-dimensional compression, isotropic and anisotropic compressions, conventional triaxial and true triaxial tests on the DEM sample. The results show that the evolution of the degradation variable B0 is stress-path-dependent, while a new degradation variable Bσ is roughly stress-path-independent. An exponential function is recommended for Bσto describe the degradation of soil structure. -
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图 6 不同应力路径下破损参量B0随塑性体应变和塑性偏应变的演化规律
Figure 6. Evolution of degradation variable B0 versus plastic volumetric and deviator strain for DEM sample under different stress paths
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图 7 不同应力路径下破损参量B0随等效塑性应变的演化规律
Figure 7. Evolution of degradation variable B0 versus equivalent plastic strain for DEM sample under different stress paths
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