Multi-scale Study on Material Particle Size Characteristics of Source Deposit Area Based on Landslides and Debris Flows

This study investigates the particle size characteristics of materials from landslide and debris flow sources and deposits in Baoshan City, Yunnan Province. Laboratory experiments, including sieving, laser particle size analysis, mineral identification, scanning electron microscope, and X-ray diffraction, were conducted to systematically analyze soil particles within three size fractions: dgravel < 40.00 mm, dsand < 2.00 mm, and dsilt < 0.075 mm. Using multi-scale analysis, correlations among various particle size parameters, gradation characteristics, and fractal dimension were explored. The research results indicate that: (1) clay mineral content, primarily kaolinite, is influenced by regional lithology and aligns with macroscopic grading patterns. (2) The upper size limit significantly constrains particle distribution; a lower limit reduces inter-group differences. (3) Landslide deposits exhibit a relatively scattered particle size distribution, whereas debris flow deposits show a more concentrated peak. The fractal dimension (D) strongly depends on fine particle content, with clay proportion showing a positive logarithmic correlation with D. (4) Using sand-sized particles (d < 2.00 mm) instead of gravel (d < 40.00 mm) for physical and mechanical experiments is highly feasible. This multi-scale approach establishes a detailed evaluation framework that highlights differences between source and accumulation areas. It provides a theoretical and practical basis for assessing engineering properties and the potential for recycling similar disaster deposits.