Journal of Mountain Science

, Volume 14, Issue 3, pp 417–431 | Cite as

Experimental study on the moving characteristics of fine grains in wide grading unconsolidated soil under heavy rainfall

Article

Abstract

The initiation mechanism of debris flow is regarded as the key step in understanding the debris-flow processes of occurrence, development and damage. Moreover, migration, accumulation and blocking effects of fine particles in soil will lead to soil failure and then develop into debris flow. Based on this hypothesis and considering the three factors of slope gradient, rainfall duration and rainfall intensity, 16 flume experiments were designed using the method of orthogonal design and completed in a laboratory. Particle composition changes in slope toe, volumetric water content, fine particle movement characteristics and soil failure mechanism were analyzed and understood as follows: the soil has complex, random and unstable structures, which causes remarkable pore characteristics of poor connectivity, non-uniformity and easy variation. The major factors that influence fine particle migration are rainfall intensity and slope. Rainfall intensity dominates particle movement, whereby high intensity rainfall induces a large number of mass movement and sharp fluctuation, causing more fine particles to accumulate at the steep slope toe. The slope toe plays an important role in water collection and fine particle accumulation. Both fine particle migration and coarse particle movement appears similar fluctuation. Fine particle migration is interrupted in unconnected pores, causing pore blockage and fine particle accumulation, which then leads to the formation of a weak layer and further soil failure or collapses. Fine particle movement also causes debris flow formation in two ways: movement on the soil surface and migration inside the soil. The results verify the hypothesis that the function of fine particle migration in soil failure process is conducive for further understanding the formation mechanism of soil failure and debris flow initiation.

Keywords

Wide grading unconsolidated soil Fine particle migration Soil failure Landslide Debris flow initiation Flume test Heavy rainfall 

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Notes

Acknowledgement

This research was supported by the key international collaborative project of Natural Science Foundation of China (No.41520104002).

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Copyright information

© Science Press, Institute of Mountain Hazards and Environment, CAS and Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  1. 1.Department of Civil and Environmental EngineeringHong Kong University of Science and TechnologyClear Water Bay, Hong KongChina
  2. 2.China Merchants Chongqing Communications Research & Design InstituteChongqingChina
  3. 3.Fujian Academy of Building ResearchFujian Key Laboratory of Green Building TechnologyFuzhouChina
  4. 4.Fuzhou UniversityFuzhouChina

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