[H-DS07] 地すべりおよび関連現象

[HDS07-11] Role of halloysite in causing flow-like landslides: examples from New Zealand and Japan

★Invited Papers

*Max Oke Kluger¹、Vicki G Moon¹、David J Lowe¹、Masahiro Chigira² (1.School of Science/Te Aka Matuatua, University of Waikato, Hamilton, New Zealand、2.Fukada Geological Institute, Public Interest Incorporated Foundation, Honkomagome, Bunkyo-ku, Tokyo)

キーワード：Landslides, Halloysite, Soil sensitivity, New Zealand, 2018 Hokkaido Eastern Iburi Earthquake, 1949 Imaichi Earthquake

Halloysite originates typically from synthesis of the dissolution products of the weathering of glass and felsic minerals in rhyolitic (silica-rich) volcanic ash (i.e., tephra) materials under generally wet or slow-draining conditions. Halloysite-rich soils are known to support steep slopes that fail because of earthquakes or rainfall triggers. As stable slopes, halloysite-rich soils commonly exhibit high friction angles, which are dramatically reduced once failure is triggered, this property being associated with high soil sensitivities. The low post-failure friction of these materials results in flow-like landslides with long run-out distances and dimensions that are difficult to predict. Flow slides in halloysite-rich soils have been reported from various areas in East Asia, including Hong Kong, Indonesia, and Japan, and in New Zealand. It has been posited from research at the Omokoroa flow slide on the eastern coast of North Island, New Zealand, that the charge distribution of deformed spheroidal particles of halloysite plays a crucial role in forming soils with high sensitivities¹. In this invited lecture we first discuss the role of spheroidal halloysite in the formation of sensitive soils. Then we present examples of landslides that were triggered during four major earthquakes in Japan (1949 Imaichi, 2011 Tohoku, 2016 Kumamoto, 2018 Hokkaido Eastern Iburi), with special emphasis on the quantification of different halloysite particle shapes. Finally, we compare these landslides with the Omokoroa flow slide.

¹ Kluger, M.O., Moon, V.G., Kreiter, S., Lowe, D.J., Churchman, G.J., Hepp, D.A., Seibel, D., Jorat, M.E., Mörz, T. 2017. A new attraction-detachment model for explaining flow sliding in clay-rich tephras. Geology 45, 131-134.