1997 Fiscal Year Final Research Report Summary

A study on the liquefaction of gravely soils such as Masa

Research Project

Project/Area Number	08680486
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	Natural disaster science
Research Institution	Tokyo Denki University
Principal Investigator	YASUDA Susumu Tokyo Denki University, Department of Civil Engineering, Professor, 理工学部, 教授 (90192385)
Co-Investigator(Kenkyū-buntansha)	KOBAYASHI Toshio Tokyo Denki University, Department of Civil Engineering, Lecturer, 理工学部, 教授 (80147470)
Project Period (FY)	1996 – 1997
Keywords	ground / earthquake / liquefaction / sandy soil / laboratory test / case history / earthquake design
Research Abstract	Soil conditions of liquefied gravely soils by two earthquakes, 1995 Hyogoken-nambu earthquake and the 1931 Nishi-saitama earthquake was studied by several laboratory tests and literature surveys. In the Hyogoken-nambu earthquake, a gravely sand named Masa was liquefied at many reclaimed lands in and around Kobe City. Liquefaction strength of undisturbed samples was studied at first by cyclic triaxial tests. Then two kinds of efrects on the liquefaction strength of Masa, saturation ratio and alternation of strata were studied. In the first effect, undrained cyclic triaxial tests were carried out to demonstrate the difference of liquefaction strength between saturated and partial saturated samples. Test results showed that liquefaction strength increased with the decrease of saturation ratio. In the second tests, two types of samples, mixed of grains uniformly and sorted of grains into three grain sizes, were prepared. Test results showed that liquefaction strength of two types of samples had no difference. Soil investigation data and reports on the damage were collected for the 1931 Nishi-saitama earthquake. Based on these data, soil condition of liquefied sites were evaluated. Liquefied sites were mainly old river channel and natural levee. Gravely soil layrs were found at some liquefied sites.