CUI Kailin,FAN Weijia,XIANG Lingzhi,et al.Study on the Basic Characteristics and Particle Gradation Fractal Dimension of New Debris Flow Deposits in Wudu Section of Bailong River Basin[J].Journal of Disaster Prevention and Mitigation Engineering,2022,42(04):674-682.
CUI Kailin,FAN Weijia,XIANG Lingzhi,et al.Study on the Basic Characteristics and Particle Gradation Fractal Dimension of New Debris Flow Deposits in Wudu Section of Bailong River Basin[J].Journal of Disaster Prevention and Mitigation Engineering,2022,42(04):674-682. DOI: 10.13409/j.cnki.jdpme.20210120001.
Study on the Basic Characteristics and Particle Gradation Fractal Dimension of New Debris Flow Deposits in Wudu Section of Bailong River Basin
The Bailong River Basin is an area with a high incidence of debris flows in China. A large amount of solid loose materials accumulated in the valleys are prone to form debris flows under the excitation of heavy rainfall. The particle gradation of loose solid matter affects its mechanical properties which in turn have a greater impact on the initiation of debris flow. After great rainfall, large-scale shear failure in the loose accumulation body transforms into debris flow. Taking the 16 new debris flow ditches in the Bailong River Basin as the research objects, representative accumulation samples were collected, and the basic physical and mechanical parameters of the deposits were obtained through indoor geotechnical experiments. The particle gradation of the samples were analyzed by sieving and laser particle size analyzer, and the characteristics, properties, particle size fractal structure and particle gradation relationship of the debris flow deposits were analyzed by statistical graphic method, particle size fractal method and empirical formula method. The results show that: 1. The geological environment of each channel is different, and the lithology is also different, but the particle size distribution of debris flow deposits in the area has good fractal characteristics. 2. The particle size fractal dimension
D
is between 2.5 and 2.6 and increases with the increase of the clay content
P
c
, and the two variables satisfy the relationship
D
=0.115 1ln(
P
c
) +2.509 8. 3. Through empirical formulas, particle size fractal calculations, on-site survey weighing, etc., most of the debris flows in the Wudu section of the Bailong River Basin are proven to be viscous debris flows. 4. There are many clay particles in the accumulation, but the intermediate particle sizes are usually short. The accumulation generally has poor gradation and low shear strength. The physical and mechanical properties of various debris flow deposits are quite different, but their internal friction angle mostly varies between 27° and 30°, showing that the internal friction angle of debris flow deposits in this area has good similarity. In this paper, the physical and mechanical properties of new debris flow accumulations in the studied area were investigated, and the correlation between particle size fractal dimension value and particle size composition, clay content, particle gradation, and soon was accomplished based on fractal theory. This research can provide basic data support for debris flow disaster prevention and mitigation in the studied area.
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