【作者】 赵力；

【导师】 李霞；

【作者基本信息】 东南大学 ， 岩土工程， 2021， 硕士

【摘要】 颗粒材料在土木工程领域应用广泛,其内部结构离散性大,物理力学特征十分复杂。级配作为颗粒材料的基本特性之一,研究其对颗粒材料物理力学特性的影响具有重要意义。本文选择砂土材料为研究对象,基于选取的级配函数,通过离散元法研究粒径跨度和级配曲线形状参数对代表单元堆积特性及力学特性的影响,同时结合宏细观分析方法,将试样的宏观力学行为与细观结构变化联系起来。本文的主要研究内容和结论如下:(1)建立了各向同性压缩试验模型,发现试样的堆积密度随着粒径跨度的增加而增加,随着形状参数的增大表现出先增大后减小的趋势,在形状参数为0.7时达到峰值,同时该形状参数下试样的颗粒连通性较好,达到最优堆积。(2)建立了常规三轴试验模型,发现试样的抗剪强度及剪胀性随粒径跨度的增大而减小,随形状参数的增大而增大,同时级配不影响试样的临界状态应力比,但影响临界状态线在e-p’平面上的位置,粒径跨度小或形状参数大的试样临界状态线位置高,同时斜率较大。(3)细观分析后发现粒径跨度的增大使得体系内悬浮颗粒含量增加,力学配位数降低,而形状参数对其几乎没有影响,剪切过程对粒径跨度较小或形状参数较大试样的配位数概率分布有较大影响。接触力网络中弱接触占大多数,对大颗粒携带的强接触起到支撑作用,粒径跨度较大或形状参数较小的试样接触力分布范围更广。(4)临界状态下组构张量与应力张量的联合不变量与平均主应力有唯一对应关系,并且是级配相关的,随着粒径跨度的增大或形状参数的减小而下移。基于应力—力—组构关系发现试样在临界状态下的各向异性参数与级配无关,趋向于同一值,从细观尺度解释了临界状态应力比相同的现象。(5)验证了状态相关本构模型的适用性,分析了部分模型参数的级配相关性,提出了考虑粒径跨度及级配曲线形状参数的临界状态线预测模型并验证。更多还原

【Abstract】 Granular materials are widely used in the field of civil engineering,with large discrete internal structures and complex physical and mechanical characteristics.Particle size distribution is one of the basic characteristics of granular materials,and it is of great significance to study its influence on the physical and mechanical properties of granular materials.This study is focus on sand materials,based on the selected gradation function,the discrete element method is used to study the influence of particle size span and gradation curve shape parameters on the packing characteristics and mechanical characteristics of the representative volume element.At the same time,combined with the macro-micro analysis method,the macroscopic mechanical behavior of the specimen is related to the microstructure change.The main research contents and conclusions of this article are as follows:(1)An isotropic compression test model was established,and it is found that the packing density of the sample increases with the increase of the particle size span,and shows a trend of first increasing and then decreasing with the increase of the shape parameter,reaching the peak when the shape parameter was 0.7.At the same time,the particle connectivity of the sample under this shape parameter is better,and the optimal packing is achieved.(2)A conventional triaxial test model was established,and it is found that the shear strength and dilatancy of the sample decreases with the increase of the particle size span,and increases with the increase of the shape parameter,and the gradation dose not affect the critical stress ratio of the sample,but affects the position of the critical state line on the e-p’plane.The critical state line of the sample with a small particle size span or a large shape parameter has a higher position and a larger slope.(3)After micro analysis,it is found that the increase of the particle size span increases the content of floating particles in the system,and the mechanical coordination number decreases,while the shape parameter has almost no effect on it.The shearing process has a greater impact on the probability distribution of the coordination number of the sample with a smaller particle size span or a larger shape parameter.In the contact force network,the weak contact accounts for the majority,which supports the strong contact carried by the large particles.The contact force distribution range of the sample with a larger particle size span or a smaller shape parameter is wider.(4)The joint invariant of the fabric tensor and the stress tensor in the critical state has a unique corresponding relationship with the average principal stress,and is gradation-related,and moves downward with the increase of the particle size span or the decrease of the shape parameter.Based on the stress-force-fabric relationship,it is found that the anisotropy parameters of the sample in the critical state have no relation with the gradation,and tend to the same value.The phenomenon of the same critical state stress ratio is explained from the micro-scale.(5)The applicability of the state-dependent constitutive model is verified,the gradation correlation of some model parameters is analyzed,and the critical state line prediction model considering the particle size span and the shape parameters of the gradation curve is proposed and verified.更多还原