摘要
脆性颗粒材料的多尺度模型一般包含微观尺度的基本粒子、细观尺度的颗粒和宏观尺度的颗粒堆积体3个尺度。基于离散元方法(DEM)构建多尺度模型,并将该模型应用于动态加载。首先,对多尺度模型所涉及的两种接触模型和两种黏结模型的参数进行分析,详细讨论微细观模型参数与宏观材料常数之间的联系。然后,选用Hertz-Mindlin接触模型[1]和平行键黏结模型,建造石英砂的动态多尺度模型。通过选择合适的强度和局部阻尼参数发现,模型宏细观尺度上的动态压缩响应与对石英砂的相关试验结果吻合很好。利用多尺度模型和选定的参数,探讨与动态加载密切相关的局部阻尼机制对多尺度模型各个尺度上力学响应的影响。结果表明,阻尼越大则颗粒材料对波的衰减能力越强,但过高的阻尼会使团簇强度和模型的宏观压缩曲线都表现出异常的加载速度效应(后者实际是阻尼引起的微惯性效应)。另外,高阻尼会过度衰减颗粒破碎过程产生的应力波,从而阻碍颗粒破碎。最后,应用改进的动态多尺度模型,对脆性颗粒材料的动态破碎特性进行研究,发现该模型不但能给出与试验相吻合的颗粒级配曲线,还能揭示出颗粒破碎过程中微裂纹分布的空间不均匀性,即颗粒破碎过程中波的产生机制和衰减机制相互作用导致的微裂纹聚团分布的现象。
The multiscale model for brittle granular materials generally involves three scales： elementary particles at the microscale, grains at the mesoscale, and grain piles at the macroscale. The multiscale model was created based on the discrete element method （DEM）. To apply it to dynamic loading, parameters for two contact models and two bonding models were firstly analyzed, and connections between the micro and meso model parameters and the macro material constants were also discussed. Then, the dynamic multiscale model for quartz sand was created with the Hertz-Mindlin contact model and the parallel-bond model. Through selecting appropriate strength and local damping parameters, it is observed that the dynamic compression properties of the simulated sand agree well with the experimental results on quartz sand at both the meso and macro scale. With the calibrated model, the influence of the local damping mechanism which is closely related to dynamic loading, on the dynamic responses of the multiscale model was investigated. Results show that a higher damping level results in a stronger wave-attenuation ability of brittle granular materials. However, excessively high damping will result in an aberrant loading-velocity effect at both the meso and macro scale （the latter is actually the micro inertial effect induced by high damping）. In addition, high damping can attenuate the waves emitted during the particle breakage process and reduce the breakage extent. At last, the multi-scale model was slightly modified and used to study the dynamic particle breakage property of brittle granular materials. The modified model can yield grain-size-distribution curves consistent with the experimental ones. Moreover, it can reveal the heterogeneous distribution of particle breakage at the space scale, which refers to the clustering phenomenon of microcracks caused by the, interactions between the wave-producing and wave-attenuation mechanism in the particle breakage process.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2013年第4期922-932,共11页
Rock and Soil Mechanics
基金
国家自然科学基金资助(No.40874093
No.90916026)
高等学校博士学科点专项科研基金资助(No.20113402110008)
关键词
脆性颗粒材料
动态多尺度模型
颗粒破碎
动态加载
阻尼
brittle granular material
dynamic multi-scale model
particle breakage
dynamic loading
local damping
