Japan Geoscience Union Meeting 2015

Presentation information


Symbol H (Human Geosciences) » H-DS Disaster geosciences

[H-DS25] Geohazards in humid, tectonically active countries and their precursors

Wed. May 27, 2015 12:00 PM - 12:45 PM 101A (1F)

Convener:*Masahiro Chigira(Disaster Prevention Research Institute, Kyoto University), Satoru Kojima(Department of Civil Engineering, Gifu University), Hiroshi YAGI(Faculty of Art, Science and Education, Yamagata University), Taro Uchida(National Institute for Land and Infrastructure Management), Chair:Tomoyuki Iida(防災科学技術研究所), Hiroshi Kobayashi(Aero Asahi Corporation)

12:33 PM - 12:36 PM

[HDS25-P14] Soil structure and shallow landslides on hillslopes underlain by granite and hornfels

3-min talk in an oral session

*Takuma WATAKABE1, Yuki MATSUSHI2, Masahiro CHIGIRA2, Ching-ying TSOU2, Yasuto HIRATA1 (1.Graduate school of science, Kyoto University, 2.Disaster prevention research institute, Kyoto University)

Keywords:shallow landslides, granite, hornfels, soil stracture

In 22 August 2014, a heavy rainstorm triggered numerous shallow landslides and debris flows in hillslopes of granite and hornfels in Hiroshima, southwest Japan. The landslide density was larger in granite area than in hornfels area even they received almost same rainfall amount (~150 mm/3h). Soil thickness on hornfels was thicker than that on granite. We investigated hillslope with shallow landslides to understand the difference in soil layer structure and soil properties. In the granite area, hydraulic conductivity ranged 10-5-10-2 cm/s, decreasing gradually with increasing soil depth. In the hornfels area, hydraulic conductivity ranged 10-8-10-4 cm/s and impermeable layer emerged just below the slip surface. These results suggest that soil properties are different between granite and hornfels. The soil from hornfels contains finer in grain size, higher in clay and more cohesive minerals than that from granite. These differences may affect the subsurface water behavior and slope destabilization process in each area, and hence potential of shallow landsliding by heavy rainstorms.