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对于岩土类的颗粒材料,在特定的应变加载路径下会发生非局部化的失稳现象,此时应力状态处于Mohr-Coulomb屈服面内,试样整体急剧失稳。采用颗粒离散元方法,研究抗转动特性对颗粒材料在等比例应变加载路径下宏、细观力学特性的影响。模拟发现,较为松散的试样更易发生分散性失稳,此时颗粒集合体的应力-应变状态满足Hill材料失稳准则。采用考虑颗粒转动的接触模型进行离散元模拟,通过改变颗粒间接触的转动摩擦系数,从宏观和细观层面分析等比例应变加载路径中颗粒材料的稳定性。颗粒抗转动能力的增强可以降低材料发生分散性失稳的可能性,随着转动摩擦系数的增加,应力路径由应变软化逐渐转为应变硬化,原本会发生分散性失稳的松散颗粒集合体表现出与密实颗粒集合体相似的宏观力学特性;颗粒集合体的内部结构表现出相应的细观作用机制,转动摩擦系数的增加有效地抑制了颗粒转动,虽然降低了颗粒体系的配位数,但增加了颗粒之间的接触力,增强了颗粒体系力链结构的稳定性和各向异性,形成稳定的结构持续抵抗外荷载的施加,从而试样整体不会形成松散的接触状态而失去稳定性。
For the geotechnical granular material, the non-localized instability occurs under the specific strain loading path, and the stress state is in the Mohr-Coulomb yield plane, and the whole specimen is rapidly unstable. The influence of the anti-rotation property on the mechanical properties of macroscopic and micromechanical properties of granular materials under equal strain loading is studied by using the particle discrete element method. The simulation shows that the loose specimens are more susceptible to dispersion instability, and the stress-strain state of the particle aggregates satisfies the Hill material instability criterion. Discrete elemental modeling is carried out by using the contact model considering particle rotation, and the stability of the granular material in the equal-strain loading path is analyzed from the macroscopic and meso-scale aspects by changing the rotational friction coefficient of the contact between the particles. Increasing the anti-rotation ability of particles can reduce the possibility of dispersion instability of materials. With the increase of rotational friction coefficient, the stress path gradually changes from strain softening to strain hardening, and loose particle aggregates, The macroscopic mechanical properties are similar to those of the dense particle assembly. The internal structure of the particle assembly shows a corresponding meso-mechanism. The increase of the rotational friction coefficient effectively suppresses the rotation of the particles. Although the coordination number of the particle system is reduced, Increases the contact force between the particles and enhances the stability and anisotropy of the force chain structure of the particle system to form a stable structure that continuously resists the application of external loads so that the whole sample will not form a loose contact state and lose stability .