Abstract: The content of breakstone in red-bed mudstone has a direct influence on the rheological property, permeability, strength and subgrade deformation of the fillings after compaction. To investigate the fractal features of red-bed mudstone, we analyzed the particle size distribution, crushing rate, and fractal dimension of red-bed mudstone specimens of different moisture contents and coarse grain to fine grain ratios after compaction test. Results reveal that the particle size distribution of crushed mudstone is of typical fractal features, with the fractal dimension ranging between 2.418 and 2.529. With the increase of moisture content, the rate of crushing and the fractal dimension both increase correspondingly. When the initial content of P₅ is relatively large, moisture content has a big influence on the growth of fractal dimension, but with the increase of initial coarse grain, the growth of fractal dimension slows down. Therefore we conclude that the rate of crushing and the fractal dimension have some correlation following the Gaussian normal distribution. They both increase with the increase of moisture content, and are in negative relationship with the initial content of P₅.

Key words: red-bed mudstone, compaction test, crushing of particles, rate of crushing, fractal features, normal distribution