考虑颗粒强度尺寸效应的堆石体缩尺效应研究

Scale effects of rockfill materials considering size effect of particle strength

统计分析了国内外堆石体尺寸效应室内试验研究成果,认为采用相同试验颗粒来源及相同制样方法时,缩尺效应主要是由颗粒强度的尺寸效应所产生。将能够描述不同粒径颗粒的强度表达式引入到服从Weibull分布的生存概率模型,并以此来考虑颗粒强度的尺寸效应。采用连续-离散耦合分析方法,研究了颗粒强度的尺寸效应对堆石体室内试验缩尺效应的影响,从细观层面揭示了室内试验尺寸效应的产生机制。数值模拟结果表明:缩尺效应主要是由法向接触力各向异性差异造成的;在相同颗粒强度尺寸效应参数?下,峰值内摩擦角随最大粒径的增大而减小,而破坏点对应的体积应变呈现出相反的变化趋势;对于同一尺寸试验,峰值内摩擦角随颗粒强度尺寸效应参数?的减小而减小,体积应变随?的减小而增大;考虑颗粒强度尺寸效应后,颗粒强度c?随粒径的增大而减小,颗粒平均法向和切向接触力随最大粒径的增大而增大,因此不同尺寸试样表现出明显的缩尺效应。

By statistical analysis of previous studies and laboratory tests on scale effects of rockfill materials, it could be argued thatthe size effect of particle strength should be the major cause for the scale effect obtained in the condition of the same particle source and the same sample preparation method. Then, in this study an expressionfor describing the strength of particles with different sizes was integrated into a survival probability model based on the Weibull distributions, and the size effect of particle strength was calculated using a combined finite-discrete element method （FDEM）. The mechanism of scale effect was also examined at meso-scopic level. The simulation results show that the scale effect was dominated by anisotropy in normal contact force. With the same size effect parameter of particle strength, peak internal friction angle was decreased with the increasein the maximum particle size, while volume strain at damage point took a reverse trend. For the tests of same particle size, a decrease in the size effect parameter led to a decrease in peak internal friction angle but an increase in volume strain. When the size effect of particle strength was considered, increasing the maximum particle size caused the particle strength to decrease and the average particle normal and tangential contact forcesto increase. This explains why particles with different sizes show an obvious scale effect in laboratory tests.