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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。
Soil is a complex particle system with significant grain-scale effects on its strength and deformation. In order to consider the influence of soil particles with different scales on the macroscopic mechanical properties of soil, according to the cohesion and frictional physical effects caused by the interaction between soil particles, the soil-particle-scale hierarchy is divided to construct the soil that reflects the information of soil material and particle features Based on the characteristics of mechanical response at different levels of soil structure, the concept of coordinating microcracks was introduced and a soil cell model with multi-scale hierarchical theory was established to solve the deformation between different scales And stress conversion relations, the micro-mechanics theory from qualitative analysis to the level of quantitative analysis. In this paper, a series of direct quick shear tests were carried out on soil remnant remnants with different combinations of particles to test the particle scale effect of the direct shear mechanics characteristics of soil. Simultaneously, The strain gradient and intrinsic scale and other micro-model parameters. The test results show that the yield strength of soil increases with the increase of soil particle fraction. When the soil mass fraction is relatively small (≤0.125), the yield strength of soil increases slightly with the decrease of particle size. When the mass fraction of reinforcing particles is relatively large (≥0.177), the yield strength of soil increases slightly with the increase of particle size. Strengthening the particle-induced strain gradients and coordinating microcracks in the adjacent matrix is a micro-physical mechanism that produces particle-scale effects on soil mechanics. Calculation formula of soil shear yield strength established by soil cell model. Preliminary consistency between test results and model prediction.