摘要
颗粒破碎是影响砂土宏-微观力学性质的重要因素。采用改进型的可破碎颗粒生成方法,通过设置不同强度的平行黏结键模拟不同强度的可破碎颗粒,并借用基于离散元方法(DEM)的双轴压缩试验详细研究了可破碎性土在剪切过程中颗粒破碎率/平均破碎程度、微观尺度上的能量耗散分配机制、剪切破碎带形成以及断裂键各向异性的演化过程。结果表明,颗粒破碎强烈地影响砂土在宏观尺度上的力学响应、颗粒尺度上的能量分配机制以及剪切过程中的颗粒的组织结构演化。颗粒破碎主要影响小应变阶段各能量耗散元的分配机制,而在临界状态下剪切带内的颗粒摩擦以及破碎耗能是消耗外界功的主要因素。数值结果亦表明,颗粒的破碎伴随着整个剪切过程,但破碎率的增长速度却随着剪切应变的发展逐渐降低。另外,在剪切过程中,对于低破碎性土,在临界状态下剪切破碎带基本形成,带内的原有组织结构被打乱,断裂键的各向异性也随之弱化。
Detailed knowledge of crushability evolution and particle-scale energy allocation behavior under the influence of particle breakage is of fundamental importance to the development of micromechanics-based constitutive models of sands. This study reports original results of the particle development, energy input/dissipation and shear band formation of idealized crushable sands using 2D discrete elements simulations. Particle breakage is modeled as the disintegration of synthetic agglomerate particles which are made up of parallel-bonded elementary discs. Simulation results show that the particle crushability strongly affect the mechanical response in macroscopic level and energy allocation in particle-scale level of the soil both at small and large strains. The major role of particle breakage, which itself only dissipates a negligible amount of input energy, is found to advance the soil fabric change and promote the inter-particle friction dissipation. At large strains where particle breakage is greatly reduced, a steady energy dissipation by inter-particle friction and mechanical damping is observed. Furthermore, it is found that the amount of particle breakage keeps increasing during the whole shearing process;but the rate of particle breakage decreases gradually with the applied axial strain. And a clear shear band can be found in low-crushable soil and the anisotropy of the broken bonds becomes weaker and weaker as the development of shearing.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2014年第9期2709-2716,共8页
Rock and Soil Mechanics
基金
地质灾害防治与地质环境保护国家重点实验室开放基金项目(No.SKLGP2012K019)
国家自然科学基金青年基金项目(No.51109182)
国家自然科学基金(No.41372296)
科技部十二五支撑计划项目(No.2012BAK10B02)
关键词
离散元
破碎率
能量耗散
剪切带
各向异性
discrete elements
crushing ratio
energy dissipation
shear band
anisotropy
