Features and mechanism of slope failure induced by the 2017 July Northern Kyushu torrential rainfall disaster in Japan

Shigeo Yamamoto, H. Hemanta

Research output: Contribution to conferencePaperpeer-review

Abstract

The torrential rain which occurred on July 5-6, 2017 in northern Kyushu (Fukuoka and Oita Prefecture), caused many landslides, debris flows and flooding of rivers. Especially, Asakura City in Fukuoka Prefecture suffered extensive damage, and a large amount of sediment movement was observed in the Akatani River and its tributary; the Otoishi River. In this research, detailed field survey in those areas was conducted and occurred slope failures were classified, then the mechanism of each failure was discussed. Based on the results, it is revealed that there was the difference of failure type between the distribution area of granite and crystalline schist. In the area of granite, it can be categorized into two types: surface failure of hardly weathered granite; and bedrock failure. On the other hand, in the area of crystalline schist, it can be classified into 3 types: collapse of surface failure; failure relating to fault; and large-scale of landslide. Among those types of failure, surface failure of weathered granite was mostly observed. Samples were also collected from the representative area and constant volume direct shear test was conducted. The test results revealed that the value of apparent internal friction angle was low, and it is found that the mass movement from the surface failure in granite areas can be highly fluidized soil. This is consistent with the result of observation which decomposed granite soil were flowed in the basin of those rivers. Therefore, it is considered that the mechanism of the slope failure in the region of granite is fluidized failure with long travel distance.

Original languageEnglish
Publication statusPublished - 2020
Event16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019 - Taipei, Taiwan, Province of China
Duration: Oct 14 2019Oct 18 2019

Conference

Conference16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019
Country/TerritoryTaiwan, Province of China
CityTaipei
Period10/14/1910/18/19

All Science Journal Classification (ASJC) codes

  • Geotechnical Engineering and Engineering Geology

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