A FRACTAL IVIODEL FOR SOIL PARTICLES AGGREGATES

We propose a scaling model far incoherent soil particles aggregates. We assume that the surface of the aggregate fraction whose characteristic length is greater than x is scaled by a factor x 2 -D. Consequently we derive an expression far the sediment grading curve which is valid between an inner and an outer cutoff length scales. The proposed probability distribution is proved to fit a wide nu1nber of soil samples coming out from different geological environments. A number of soil samples are then numerically simulated under the assumption of a settling process driven by the gravity action only. The resulting aggregates are then regarded as porous media and their geometrical characteristics are analyzed. Particularly the void volume is found to be scaled by a factor x3-D. By means of the usual Carman approach a simple expression is derived for the hydraulic conductivity. This is found to depend upon the inner and outer cutoffs and the parameter D only. This last can be regarded as a fractal dimension typical of each aggregate. A number of rock fragmentation models are then reviewed which are in agreement with our work. Particularly the physical meaning of D is discussed for these fractal aggregates as a .. trace of the1r morphogenetic process.