基于颗粒流数值试验的岩土材料内尺度比研究

内尺度比是材料的最小结构和材料尺寸的比。在细观条件下,岩土材料可以看成是由不同尺度矿物颗粒组成的颗粒集聚体,含有不同尺度的天然缺陷。这些带有尺度特点的材料结构、构造特征无疑会影响岩土材料性质测试的结果和准确性,即岩土材料具有和金属材料一样的内尺度比。利用颗粒流软件fish语言编写程序虚拟实现了岩土材料单轴压缩试验,设计了0.05、0.10、0.20、0.40、0.60、0.80、1.00、1.20、1.40、1.60、1.80、2.00 mm等12种粒径数值试件,分别进行了单轴压缩试验。根据试件的破坏形态、应力-应变曲线,分析了内尺度比对测试结果的影响,发现:粒径小于0.40 mm之后,计算时间急剧增加,计算效率急剧减小;内尺度比小于0.01之后,材料的数值试验结果趋于稳定。这说明岩土材料也存在内尺度比,岩土体的物理力学参数的尺寸效应问题就是材料内尺度问题的一种表现形式。

Study of inner scale ratio of rock and soil material based on numerical tests of particle flow code

Inner scale ratio is a ratio between minimum crystal structure of material and its specimen size. Rock and soil material, being a type of different sizes mineral particles assembler under microscopic conditions, contains different scale raw faults. These size features of material structure will affect accuracy of rock and soil material characteristics test results. That is to say there exists inner scale ratio in rock and soil materials like that of metal material. So virtual uniaxial compression test done by inner embedded fish language of particle flow code is used to study inner scale ratio of geotechnical material. Twelve numerical specimens with twelve types of grain size such as 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8 and 2.0 mm are designed and tested. According to failure shape and stress-strain curve of these specimens, effect of inner scale ratio on test results is analyzed. It is found that the computing time increases dramatically and computing efficiency decreases sharply if grain size less than 0.4 mm; and that test results tend to stability and accuracy if inner scale ratio less than 0.01, so as to prove existence of inner scale ratio in rock and soil material. Size effect in geotechnical material is reflection of inner scale ratio.