Characterizing the spatial variability of soil particle size distribution in an underground coal mining area: An approach combining multi-fractal theory and geostatistics

Abstract

Long-term underground coal mining activities results in severe surface deformation and land subsidence, altering soil physical properties significantly. Soil particle size distribution (PSD) is a fundamental physical attribute affecting many other soil properties. Therefore, understanding the variability of PSD is crucial to conduct targeted land rehabilitation. In present study, a novel method combining multi-fractal theory and geostatistics was advanced to characterize the spatial variability of soil PSD in a coal-mined subsidence area. Three independent field plots, i.e., one unmined plot (UMP), one subsided plots (SUP), and one reclaimed plot (RCP), in NO.3 Pingshuo Anjialing underground coal-mine in Shanxi province of China, were selected to perform this study. Four multi-fractal attributes of PSD of individual soil samples, i.e., D(0), D(1), Δα(q) and Δf(α), in three plots were calculated, and geo-statistics was employed to quantify the spatial variability of multi-fractal attributes of PSD. This combining method showed some advantages in characterizing the variability of soil PSD compared to single multi-fractal, single geo-statistics or traditional statistics, and it can characterize the spatial variability of overall PSD characteristics in detail, quantifying the spatial variability of soil PSD range, PSD concentration degree, PSD non-uniformity, and PSD non-symmetry. The soil PSD range, PSD concentration degree, PSD non-uniformity and PSD non-symmetry in this underground coal mining area didn't present a high spatial variability. Combining multi-fractal theory and geostatistics is an effective method to characterize the spatial variability of soil PSD in underground coal-mine area, and this method is universal and can be popularized and applied in other unmined areas.