Title : Study of an unsaturated slope failure due to rainfall infiltration in wenshan district of taipei city

Page : PP.277-286

Author(s) : Horn-Da Lin, Jhih-Rou Huang, Wei-Chien Wang, and Chao-Wei Chen

Keyword : Unsaturated soil; rainfall infiltration; hydrological responses; slope stability; colluvium

Abstract : 

Traditionally, the analysis of the rainfall-induced slope failure was assumed to be under saturated condition. Nevertheless, lots of colluvium slopes are unsaturated in the normal condition in Taiwan. Unsaturated slopes have matric suction, contributing to their high slope stabilities in the dry season. With the rainfall infiltration, the decrease of matric suction may lead to the failure of the slope. This paper presents the numerical analysis of a case located in Wenshan Dist., Taipei City, Taiwan. The slope collapsed during Typhoon Jangmi in September 2008. Since the remediation program was urgent then, there was not enough time to comprehensively figure out the failure mechanism of the case. Consequently, this study conducts the site investigation and performs the numerical analysis to better understand the real failure mechanism of this slope. Results reveal that the failure is shallow and progressive. Additionally, the toe of colluvium was the most susceptible part of the whole slope during infiltration. Furthermore, the critical volumetric water content existed, when the slope collapsed. Accordingly, the monitoring system ought to be set in the toe of the colluvium and the volumetric water content may be considered as an index parameter for the early warning system of landslide disasters in the future.

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