The Grain-size distribution and structural dimension analysis of the accumulation zone of the debris flow was accomplished with the graphic method and fractal theory. Results show that the giant debris flow deposits in Hou gully

Xiongjia gully and Majingzi gully are bad sorting

very bad sorting

and very bad sorting

and the components mainly consist of deposit coarse grain. According to fractal theory

it can be known that those three giant debris flow gullies are viscous

and their grain sizes are non-uni-form. Results show that comprehensive utilization of grain-size distribution and structural dimension analysis could understand sorting

grain-size distribution and type of "7·4" giant debris-flow deposits very well. It also can provide reference data to formation

movement

accumulation characteristics

numerical simulation

etc.