Investigation of shallow landslides triggered by heavy rainfall during typhoon Wipha (2013), Izu Oshima Island, Japan

Hufeng Yang,Masakatsu Miyajima,Fawu Wang

doi:10.1186/s40677-015-0023-8

Hufeng Yang, Masakatsu Miyajima + Show 1 more

Open Access

https://doi.org/10.1186/s40677-015-0023-8

Copy DOI

Abstract

Typhoon Wipha struck Izu Oshima Island on 16 October 2013, bringing heavy rainfall. It triggered widespread landslides on the western slopes of Izu Oshima Island, and caused significant loss of life and serious property damage. Authors have conducted both field investigations and laboratory experiments in an effort to understand the initiation mechanism of the shallow landslides triggered by heavy rainfall. Pyroclastic-fall deposits on the slopes are well-graded fine sand with silt, and with high specific gravity and void ratio. These soil properties will affect the mechanical and hydraulic characteristics of soil. The results of consolidated-undrained triaxial tests show that the effective internal friction angle of soil is 38.7 degrees. The results of triaxial tests using pore-water pressure control show that static liquefaction can occur in porous pyroclastic-fall deposit layers due to rainfall infiltration. The effective strength of pyroclastic-fall deposits on the upper slope is quite high. Even though the slope is very steep (over 30 degrees), it can remain stable while in an unsaturated condition. Due to heavy rainfall and the porosity of the pyroclastic-fall deposits, rainfall can quickly infiltrate into soil layer. Moreover, the interface above the underlying basalt will stop groundwater infiltration, acting as an impervious boundary. With increase of groundwater level, the effective strength of the porous soil will decrease. Finally, static liquefaction can be triggered, leading to the generation of shallow landslides on the upper slopes.

Highlights

Typhoon Wipha struck Izu Oshima Island on 16 October 2013, bringing heavy rainfall
Grain size distribution of sample shows that the soil is well-graded fine sand with silt (ASTM D2487-06 2006)
After the occurrence of shallow landslides, these fine materials on steep slopes can transform into debris flow during heavy rainfall

Summary

Introduction

Typhoon Wipha struck Izu Oshima Island on 16 October 2013, bringing heavy rainfall It triggered widespread landslides on the western slopes of Izu Oshima Island, and caused significant loss of life and serious property damage. Authors have conducted both field investigations and laboratory experiments in an effort to understand the initiation mechanism of the shallow landslides triggered by heavy rainfall. Most regions on the typhoon track, especially the Izu Oshima Island, suffered heavy rainfall It triggered widespread shallow landslides on the western slopes of Izu Oshima Island (Fig. 2). High speed debris flows flooded the settlement of Motomachi, which is situated at the toe of the slopes This disaster caused serious loss of life and property damage.

Methods

Results

Discussion

Conclusion