堆石料单粒强度尺寸效应的颗粒流模拟方法研究

Numerical simulation of effect of size on crushing strength of rockfill grains using particle flow code

围绕堆石料单粒强度尺寸效应的颗粒流模拟方法展开研究。首先,基于FISH二次开发建立了堆石料的随机不规则单粒模型,充分考虑堆石料的形状特征和破碎现象;然后,建立了堆石料单粒强度尺寸效应的等效模拟方法,以单粒强度随其粒径的变化规律为基础,推导了堆石料模型中细观黏结强度与堆石料等效粒径的负指数经验公式;其次,基于建立的数值模型对堆石料的室内单粒压缩试验进行仿真模拟,验证数值模型的正确性和合理性,并对较大粒径堆石料的单粒强度进行模拟预测,突出数值试验的优势;最后,基于建立的数值模型对相同粒径不同形状特征堆石料的单粒强度分布特征进行模拟研究。研究结果表明:(1)堆石料内部缺陷含量和尺寸随粒径增加对其单粒强度所产生的尺寸效应,可通过堆石料模型中细观强度参数随粒径折减进行等效模拟;(2)形状特征对堆石料的破裂机制具有重要影响,方形颗粒为压剪破裂,单粒强度较高,而随机不规则颗粒和圆形颗粒为拉剪或劈裂,单粒强度相对较低;(3)拉剪或劈裂条件下,堆石料形状越不规则,其单粒强度的离散程度越高,反之则离散程度越低。相关研究成果可为进一步研究荷载作用下堆石体内各粒径段堆石料的破碎量奠定基础,从而更加真实地反映堆石体的级配演化规律。

Effect of size on crushing strength of rockfill grains is studied using the particle flow code. Firstly, a discrete model of rockfill grains is developed using secondary development method with FISH language, in which particle shape and breakage behavior of rockfill grains are replicated reasonably. Then an equivalent simulation method is proposed to investigate the effect of size on crushing strength of rockfill grains in various particle sizes. A negative power formula is presented to describe the relationship between crushing strength of rockfill grains and its particle sizes. The meso bond strengths of contacts inside an aggregate model of rockfill grain are dependent on the size of the aggregate itself. Then, one dimensional compression tests of rockfill grains in lab are replicated based on the proposed numerical method to verify its accuracy and validity. At the end, influence of shape of rockfill grains on distribution of crushing strength is studied. Several basic conclusions are obtained： 1） Size effect on crushing strength of rockfill grains due to microcracks can be simulated equivalently by the way that meso strength of contact in the numerical model of rockfill grains decreases while the size of rockfill grains increases; 2） Crushing mechanical of rockfill grains is influenced by the particle shape, and square grains are usually crushed in compression-shear mode, while irregular and round grains fail in tension-shear or splitting mode. As a result, crushing strength of square grain is usually much higher than that of irregular and round grain; 3） When fail in tension-shear or splitting mode, dispersion of crushing strength of rockfill grains is dependent on shape of rockfill grains. The regular particle shape presents higher Weibull modulus, indicating smaller divergence for the crushing strengths. The breakage behavior of rockfill grains with different sizes under load provides a reasonable method to predict the evolution of particle size distribution of rockfill assembly.