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T. Kokusho
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Geotechnical damage due to the 2016 Kumamoto Earthquake and future challenges H. Hazarika; T. Kokusho; R.E. Kayen; S. Dashti; H. Fukuoka; T. Ishizawa; Y. Kochi; D. Matsumoto; H. Furuichi; T. Hirose; T. Fujishiro; K. Okamoto; M. Tajiri; M. Fukuda
Lowland Technology International Vol 19 No 3, Dec (2017)
Publisher : International Association of Lowland Technology

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The 2016 Kumamoto earthquake with a moment magnitude of 7.0 (Japanese intensity = 7) that struck on April 16 brought devastation in many areas of Kumamoto Prefecture and partly in Oita Prefecture in Kyushu Region, Japan. The earthquake preceded a foreshock of magnitude 6.5 (Japanese intensity = 7) on April 14. This paper summarizes the damage brought to geotechnical structures by the two consecutive earthquakes within a span of twenty-eight hours. The paper highlighted some of the observed damage and identifies reasons for such damage. The geotechnical challenges towards mitigation of losses from such earthquakes are also suggested.
Evaluation of seismically induced slope displacement by energy approach and applicability to a Case Study related to the 2016 Kumamoto Earthquake T. Ishizawa; T. Kokusho
Lowland Technology International Vol 19 No 4, March (2018)
Publisher : International Association of Lowland Technology

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The energy approach for slope failure evaluation has been developed by examining the energy balance in the rigid block model, comparing it to innovative shake table tests of sand model slope. As a result, previous studies have shown evaluation method is proposed in which residual slope displacement can be given from the earthquake energy. Moreover, a framework of performance-based design for slopes during earthquakes has been proposed. However, this energy method needs to have more research to upgrade the energy method to a reliable design tool. Therefore, the energy-based method was applied to a case history during the 2016 Kumamoto earthquake. The input earthquake energy defined as a base layer of the slope was extrapolated from severalstrong motion records. This paper discusses applicability of the energy-based method to a case history, during the 2016 Kumamoto earthquake, of the sliding-mass was travelled gentle slope along the clear slip plane, as a simplified rigid block model.
Deformation and failure characteristics of Volcanic soil at landslides site due to the 2016 Kumamoto Earthquake W. O. Sumartini; H. Hazarika; T. Kokusho; S. Ishibashi; D. Matsumoto; B. Chaudhary
Lowland Technology International Vol 19 No 4, March (2018)
Publisher : International Association of Lowland Technology

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A chain of earthquakes with a maximum moment magnitude of 7.3 MW struck Kumamoto prefecture and its vicinity from April 14-16th, 2016. It generated widespread landslides not only on steep slopes but also on gentle slopes. The landslides caused huge damages to nature, infrastructure, and loss of lives. Thus, it is crucial to determine the failure mechanism of those slopes which were formed by volcanic soil and to elucidate the effect of cyclic loading on strength characteristics of the soil. A series of investigations of the soil, which is orange colored, was conducted. Undrained static and cyclic triaxial tests were performed. Also, x-ray powder diffraction test, x-ray fluorescence test, and scanning electron microscope test were performed for further understanding of the material behavior. The triaxial test revealed semi dilative behavior under monotonic loading with small confining stress and contractive behavior on high confining stress. In the cyclic triaxial tests under in situ confining stress, cyclic mobility by lower cyclic stress and flow failure by higher cyclic stress was observed. Also, soil fabric, chemical composition, and mineral composition, which describe the deformation behavior and failure characteristics of the soil has been reported.
Analysis of liquefaction of volcanic soil during the 2016 Kumamoto Earthquake based on boring data K. Ogo; H. Hazarika; T. Kokusho; D. Matsumoto; S. Ishibashi; W. O. Sumartini
Lowland Technology International Vol 19 No 4, March (2018)
Publisher : International Association of Lowland Technology

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On April 16th, 2016 Kumamoto earthquake registering 7 on Japanese scale caused liquefaction in many places around Kumamoto plain. However, considering the magnitude and the distance from the hypocenter, the liquefaction-induced damage was not so huge. Most of sand boiling was observed where liquefaction is likely to happen such as near waters and on an old river channel. In addition, black sand which seems to be volcanic soil was observed as ejecta of liquefaction in many places. This paper deals with the liquefaction characteristics of volcanic soil through physical and mechanical testing, microscopic observation by SEM and liquefaction susceptibility evaluation based on boring data. According to the physical testing, the grain size distribution was typical of liquefaction susceptible sand. Many of sand boils happened on the alluvial ground, and the thick strata of volcanic soil were found there. Based on the results of liquefaction evaluation, some locations have shown the liquefaction susceptibility in spite the fact that little occurrence of liquefaction took place at those locations.
Geotechnical extreme-event reconnaissance (GEER) investigation to the 2016 Mw6.0, Mw6.2and Mw7.0 Kumamoto Japan Earthquakes R. Kayen; T. Kokusho; H. Hazarika; S. Dashti; J. R. Calderon; T. K. Franke; N. K. Oettle; B. Wham; G.P. Louis-Kayen; R. Sitar; N.M. Louis-Kayen
Lowland Technology International Vol 19 No 4, March (2018)
Publisher : International Association of Lowland Technology

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The Kumamoto, Kyushu, Japan earthquakes began with an earthquake (M6.2) on the Hinagu Fault on April 14, 2016 followed by a second (M7.0) event on the Futagawa Fault, that on April 16. These shallow 10-11 deep km events are the strongest earthquakes recorded in Kyushu prefecture during the modern instrumental era. The United States’ National Science Foundation (US NSF) supported Geotechnical Extreme Events Reconnaissance (GEER) Association conducted a reconnaissance of the region. These earthquakes resulted in substantial damage to infrastructure, buildings, cultural heritage of Kumamoto castle, roads and highways, slopes, and river embankments. Surface fault rupture produced offset to roads, buildings, river levees, and an agricultural dam. Surprisingly, given the extremely intense earthquake motions, liquefaction-induced damage was mostly limited to a few districts of Kumamoto City and in port areas, indicating that either the volcanic soils were largely unsusceptible to liquefaction or the presence of fines reduced the surficial manifestation of liquefaction and its effects. The important case histories identified by the study are [1] fault rupture through OhKirihata Dam; [2] subsidence in Aso Caldera; [3] fault rupture through Shimojin-Cho River Canal; [4] surprising paucity of liquefaction and its effects; and [5] possible identification of a nearly non-displacement lateral spread.
Co-Authors B. Chaudhary B. Wham D. Matsumoto G.P. Louis-Kayen H. Fukuoka H. Furuichi H. Hazarika J. R. Calderon K. Ogo K. Okamoto M. Fukuda M. Tajiri N. K. Oettle N.M. Louis-Kayen R. Kayen R. Sitar R.E. Kayen S. Dashti S. Ishibashi T. Fujishiro T. Hirose T. Ishizawa T. K. Franke W. O. Sumartini Y. Kochi