基于真实块石形态的土石混合体细观力学三维数值直剪试验研究

Meso-mechanics of soil-rock mixture with real shape of rock blocks based on 3D numerical direct shear test

块石形态是影响土石混合体细观结构及宏细观力学特性的一个重要因素。提出一种基于真实块石形态的土石混合体细观力学研究方法,首先采用三维扫描技术建立块石三维形态数据库,然后根据粒度组成生成试样内部块石三维空间分布模型,从而构建土石混合体的数字模型。利用所提出的基于多球颗粒均匀接触的复杂块体表征算法,实现任意复杂形态块体的多球颗粒均匀、紧密接触填充。基于上述方法,建立土石混合体离散元数值计算分析模型,并协同现场试验结果开展三维数值直剪试验研究。根据土体的现场试验结果反演得到离散元数值试验中土颗粒的细观接触力学参数,将其应用于土石混合体数值试验得到了较好的效果。通过数值试验研究表明,土石混合体在剪切过程中的块石效应,使剪切带变得更加宽厚和曲折,在宏观上造成了试样的内摩擦角有增高趋势;而由于块石含量增加,使得其黏结作用的土体含量减小,从而在宏观上表现为试样黏聚力呈略有降低趋势。

The shape of the rock block influence greatly the meso-structure and macro-meso mechanical behaviour of soil-rock mixture（S-RM）. In this paper,a method for the study of meso-mechanics of S-RM based on the real shape of rock blocks was presented. Firstly,the database of 3D geometric model of rock blocks was built based on 3D scanning technology. Then,with the database and the block size distribution,a special 3D model of S-RM with rock blocks was generated. A numerical model of S-RM sample was also generated. Furthermore,using the proposed multi-sphere modelling method of complex blocks,arbitrary particles can be modelled with the multi-spheres contacted uniformly and closely. As a result,a 3D DEM meso-structural model of S-RM sample was generated. In accordance with the field test,a series of 3D numerical direct shear tests were carried out. The meso-mechanical parameters of the soil particles used in the DEM numerical test were obtained from the field tests. The results of numerical tests indicated that the rock blocks made the shear zone of the S-RM sample wider and more zigzag than that of the soil sample,which induced the higher friction angle of the former. However, with the increase of the rock block content,the content of the fine soil particles with binding function decreased. As a result,the cohesion of S-RM was smaller than that of the soil sample.