Multiple occurrence of sand liquefaction has been reported in the past case histories worldwide, including those on the 2010-2011 Christchurch Earthquakes in New Zealand and on the 2011 Off the Pacific Coast of Tohoku Earthquake in Japan. In order to reveal the multiple-liquefaction behavior, a series of 1-g shaking table tests on level ground and another series of cyclic stacked-ring shear tests on hollow cylindrical specimen with/without initial static shear are conducted. It is observed that, though overall densification is observed in the two series of tests, the response of sands during the current liquefaction stage is more predominantly affected by the liquefaction history in the immediate-past stage. In case of the cyclic stacked-ring shear tests with initial static shear, significant effect of anisotropy induced by the immediate-past liquefaction history is also observed.
Speaker: Dr. Junichi Kosek
Dr. Junichi Koseki is a professor at Department of Civil Engineering, the University of Tokyo (UTokyo), Japan. He obtained his Bachelor, Master and Doctoral degrees from UTokyo. During the period of 1987-1994, he worked as a researcher at Public Works Research Institute, Ministry of Construction, Japan. In 1994, he moved to UTokyo as an associate professor at the Institute of Industrial Science. After promotion to professor in 2003, he moved to his current position in 2014. His research fields include liquefaction and its countermeasures, deformation and strength properties of geomaterials, and seismic behavior of earth structures. He received the C.A. Hogentogler Award from Committee D-18 on Soil and Rock, ASTM in 2000 and 2004, and the Best Paper Award from the Japanese Geotechnical Society in 2007, 2009, 2010, 2012, 2016 and 2021. He was also the 2010-2011 Mercer Lecturer endorsed jointly by the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE) and the International Geosynthetics Society, and the 2019 Bishop Lecturer of ISSMGE.