Abstract:

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.

Key words: rock and soil material, inner scale ratio, size effect, particle flow code