Multifractal characteristics of the pore structures of physically amended sandy soil and the relationship between soil properties and multifractal parameters

Pore structures of physically amended sandy soils exhibit significant multifractal characteristics, which are influenced by many soil physical properties. This study investigated the influences of adding fly ash and Montmorillonite-enriched sandstone (MS) on the physical properties and multifractal characteristics of pore structures in a sandy soil. Scanning electron microscope (SEM) was used to obtain the pore structures. MATLAB scripts were developed for calculating the Holder index (alpha(q)) and generalized dimensions (D-q) of binary SEM images. The results showed that particle compositions and water retention capacity are improved after adding the two materials. The amplitudes of D-q (Delta D) was reduced by 6.9% to 35.6% in the amended soils, which means smaller scaling diversities of pore structures. The right branches of multifractal spectrum (alpha(r)) showed higher amplitudes than that of left branches (alpha(l)), indicating that smallest pores were more diverse than the largest pores after adding the two materials. Multifractal parameters showed significant linear relationships with the sand and silt content, bulk density and total porosity. The result indicate that multifractal parameters could be used to describe the changes of pore characteristics and to quantify the characteristics of pore structures in the amended sandy soils.