NHESSD Natural Hazards and Earth System Sciences Discussions NHESSD Nat. Hazards Earth Syst. Sci. Discuss. 2195-9269 Göttingen, Germany 10.5194/nhessd-2-4487-2014 A theoretical model for the initiation of debris flow in unconsolidated soil under hydrodynamic conditions Guo C.-X. 1 2 Zhou J.-W. 3 4 Cui P. 1 Hao M.-H. 4 Xu F.-G. 4 Key Laboratory of Mountain Hazards and Surface Process, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu, Sichuan 610044, China University of Chinese Academy of Science, Beijing, 100049, China State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan 610065, China College of Water Resources & Hydropower, Sichuan University, Chengdu, Sichuan 610065, China 26 06 2014 2 6 4487 4524 Copyright: © 2014 C.-X. Guo et al. 2014 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://nhess.copernicus.org/preprints/2/4487/2014/nhessd-2-4487-2014.html The full text article is available as a PDF file from https://nhess.copernicus.org/preprints/2/4487/2014/nhessd-2-4487-2014.pdf

Debris flow is one of the catastrophic disasters in an earthquake-stricken area, and remains to be studied in depth. It is imperative to obtain an initiation mechanism and model of the debris flow, especially from unconsolidated soil. With flume experiments and field investigation on the Wenjiagou Gully debris flow induced from unconsolidated soil, it can be found that surface runoff can support the shear force along the slope and lead to soil strength decreasing, with fine particles migrating and forming a local relatively impermeable face. The surface runoff effect is the primary factor for accelerating the unconsolidated slope failure and initiating debris flow. Thus, a new theoretical model for the initiation of debris flow in unconsolidated soil was established by incorporating hydrodynamic theory and soil mechanics. This model was validated by a laboratory test and proved to be better suited for unconsolidated soil failure analysis. In addition, the mechanism analysis and the established model can provide a new direction and deeper understanding of debris flow initiation with unconsolidated soil.

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