It is very important to determine reasonably the maximum grain size, graded sizes and gradation of the coarse aggregate.

Considering the features of the construction of this line specific requirements are specified in the filling such as filling with fine earth, coarse mountain surface soil and graded crushed stones.

And it comes to a conclusion that the permeation damage slope of the coarse-grained soil of well graded with a definite proportion of fine granule is higher than that of poorly graded.