土体介质直剪力学特性颗粒尺度效应的理论与试验研究

doi:10.13722/j.cnki.jrme.2014.0742

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摘要土体是一种复杂的颗粒体系，其强度与变形具有显著的颗粒尺度效应。为考虑土体不同尺度土颗粒对其宏观力学特性的影响，根据土颗粒间相互作用产生的黏聚和摩擦物理效应，划分土颗粒尺度层次以构造反映土体内部材料信息和颗粒特征信息的土体胞元；基于土体不同尺度结构层次上力学响应的特征，引入协调微裂纹的概念，建立具有多尺度分层次理论框架的土体胞元模型，求解土体不同尺度结构层次之间的变形和应力转换关系，把微细观土力学理论从定性分析推进到定量计算的水平。采用多种颗粒组合制备土体胞元模型的饱和重塑土试样，进行一系列直接快剪试验，对土体直剪力学特征的颗粒尺度效应进行测试，同时定量计算土体胞元模型中的应变梯度和內禀尺度等微细观模型参数。试验结果表明：土体的屈服强度随加强颗粒体分比的增加而增加；当加强颗粒体分比较小时(≤0.125)，土体的屈服强度随加强颗粒粒径的减小而略为增加；当加强颗粒体分比较大时(≥0.177)，土体的屈服强度随加强颗粒粒径的增加而略为增加。加强颗粒诱发其邻近基体产生应变梯度和协调微裂纹，是土体力学特性产生颗粒尺度效应的微细观物理机制。土体胞元模型建立的土体剪切屈服强度计算公式初步验证试验结果与模型预测的一致性。

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	冯德銮1
	房营光1
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关键词 ：土力学, 颗粒尺度效应, 土体胞元模型, 多尺度框架, 物理机制

Abstract：Soil is a complex granular medium and its strength and deformation characteristics behave strong particle size effect. On the basis of the physical effects of cohesion and friction generated by the interactions between soil particles at different scales，a soil cell element that can describe the internal material information and particle characteristics of soil was constructed by dividing particle size into different scales to investigate the influence of soil particles at different scales on the macro-scale mechanical properties of soil. According to the mechanical responses of soil at various scales，the notion of coordinated micro-cracks was introduced，and a multi-scale and hierarchical soil cell element model was proposed to establish the conversion relationship of the displacement and stress between different scales. Therefore，the microscopic soil mechanics was promoted from qualitative analysis to quantitative calculation. Moreover，various soil samples with a variety particle combinations were prepared for a series of direct shear tests to study the particle size effect of soil. Meanwhile，microscopic parameters of the model such as the strain gradient and intrinsic length scale were quantitatively studied. The results show that：The yield stress of soil increases with an increase in the volume fraction of the reinforcement particles. When the volume fraction of the reinforcement particles is low(≤0.125)，the yield stress of soil increases with a decrease in the reinforcement particle size whereas when the volume fraction of these particles is high(≥0.177)，the yield stress of soil increases with an increase in the reinforcement particle size. The action of the reinforcement particles that causes the strain gradient and coordinated micro-cracks of soil to appear at the matrix joined with the reinforcement particles is the microscopic physical mechanism of the particle size effect of soil. The yield stress of soil calculated by the soil cell element model is in good agreement with that of the test result.

Key words： soil mechanics particle size effect soil cell element model multi-scale framework physical mechanism

引用本文:

冯德銮1，房营光1，2. 土体介质直剪力学特性颗粒尺度效应的理论与试验研究[J]. 岩石力学与工程学报, 2015, 34(S2): 4307-4319.
FENG Deluan1，FANG Yingguang1，2. THEORETICAL AND EXPERIMENTAL RESEARCH ON PARTICLE SIZE EFFECT OF DIRECT SHEAR MECHANICAL PROPERTIES OF SOIL. , 2015, 34(S2): 4307-4319.

链接本文:

https://rockmech.whrsm.ac.cn/CN/10.13722/j.cnki.jrme.2014.0742 或 https://rockmech.whrsm.ac.cn/CN/Y2015/V34/IS2/4307

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