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T. Uchimura
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Civil Engineering, Building, Construction & Architecture Engineering Transportation

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Experimental study on the effects of rainwater infiltration and cyclic loading on unsaturated silica sand P.H.H. Giang; T. Uchimura; L.G. Lam; W. Haegeman
Lowland Technology International Vol 17 No 4, March (2016)
Publisher : International Association of Lowland Technology

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This paper presents the result of cyclic loading tests followed by water infiltration on unsaturated sandy samples to study possible slope failures in earthquake areas. The cyclic tri-axial tests and dynamic measurements were carried out on Edosaki sand, silica sand taken from a natural slope in Chiba prefecture in Japan. The specimens were first consolidated in anisotropic condition with a principal stress ratio (K = 2), and then cyclically loaded under un-drained conditions. After cyclic loading, water infiltration was applied to the specimens until failure after different periods of waiting time. During the tests, the elastic wave velocities were continuously measured. Test results clearly show the variation of stiffness during cyclic loading and infiltration attributed to changes in relative density. Test results also confirm that there is a possible threshold value for the cyclic amplitude that causes a rearrangement of the soil skeleton and gives rise to higher failure resistance during water infiltration after reconsolidation. In short, it is very useful to monitor the stiffness and pore water pressure in a slope after an earthquake in areas with high and frequent rainfall.
An early warning monitoring of Earthquake-induced slope failures by monitoring inclination changes in multi-point tilt sensors L. Wang; S. Nishie; L. Su; H. Yamaguchi; S. Yamamoto; T. Uchimura; S.N. Tao
Lowland Technology International Vol 19 No 4, March (2018)
Publisher : International Association of Lowland Technology

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An early warning monitoring system is one of the most effective ways to reduce disasters induced by slope instability. The 2016 Ms 7.3 Kumamoto earthquake, which occurred in Kumamoto prefecture, Japan, induced more than 190 large scales of slope failures (123), debris flows (57) and landslides (10). A system of distributed tilt sensors for early warning monitoring of earthquake-induced landslides and slope failures has been proposed. Tilt angles in the surface layer of a slope were monitored using this method and, in several case studies, distinct behaviors in tilt angles in pre-failure stages were detected. Based on this behavior, it is recommended, from a regulatory perspective, a precaution be issued when the tilting rate of a slope is 0.01°/h, and a warning be issued when the tilting rate is 0.1°/h.
Co-Authors H. Yamaguchi L. Su L. Wang L.G. Lam P.H.H. Giang S. Nishie S. Yamamoto S.N. Tao W. Haegeman