Abstract: According to the specification of scale reduction, four different scale reduction methods, including scalping method, equal-weight replacement method, similar grading method and mixing method, are used to reduce the scale of a coarse-grained soil into a grading with smaller particles, namely 20 mm, 40 mm and 60 mm.. A number of the maximum dry density tests are conducted by the vibrating method. Based on the test results and fractal theory, a normalizing method is proposed to describe the relationship between maximum dry density, grading and content of fine grains. Based on the newly proposed normalizing method, the relationship of dry density versus fractal dimension before tests and the content of grains smaller than 5 mm and maximum particle size is found. According to the founded relation, the maximum dry density of the real gradation is determined. In addition, the effect of scale reduction method on the variation amplitude of grain size distribution curves of coarse-grained soil specimens before and after tests is studied. And the relationship of fractal dimension of particle breakage versus fractal dimension before tests coefficient, the content of grains smaller than 5 mm and the maximum particle size is found. Based on the newly summarized relation, the fractal dimension of particle breakage of the real gradation after filling can be determined.

Key words: coarse-grained soil, fractal dimension, gradation, maximum dry density, scale effect, particle breakage